esp32-hal-i2c.c

// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at

//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "esp32-hal-i2c.h"
#include "esp32-hal.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/semphr.h"
#include "freertos/event_groups.h"
#include "rom/ets_sys.h"
#include "driver/periph_ctrl.h"
#include "soc/i2c_reg.h"
#include "soc/i2c_struct.h"
#include "soc/dport_reg.h"
#include "esp_attr.h"
#include "esp32-hal-cpu.h" // cpu clock change support 31DEC2018
//#define I2C_DEV(i)   (volatile i2c_dev_t *)((i)?DR_REG_I2C1_EXT_BASE:DR_REG_I2C_EXT_BASE)
//#define I2C_DEV(i)   ((i2c_dev_t *)(REG_I2C_BASE(i)))
#define I2C_SCL_IDX(p)  ((p==0)?I2CEXT0_SCL_OUT_IDX:((p==1)?I2CEXT1_SCL_OUT_IDX:0))
#define I2C_SDA_IDX(p) ((p==0)?I2CEXT0_SDA_OUT_IDX:((p==1)?I2CEXT1_SDA_OUT_IDX:0))

#define DR_REG_I2C_EXT_BASE_FIXED               0x60013000
#define DR_REG_I2C1_EXT_BASE_FIXED              0x60027000

/* Stickbreaker ISR mode debug support

ENABLE_I2C_DEBUG_BUFFER
  Enable debug interrupt history buffer, fifoTx history buffer.
  Setting this define will result in 2570 bytes of RAM being used whenever CORE_DEBUG_LEVEL
  is higher than WARNING. Unless you are debugging a problem in the I2C subsystem,
  I would recommend you leave it commented out.
  */

//#define ENABLE_I2C_DEBUG_BUFFER

#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO) && (defined ENABLE_I2C_DEBUG_BUFFER)
#define INTBUFFMAX 64
#define FIFOMAX 512
static uint32_t intBuff[INTBUFFMAX][3][2];
static uint32_t intPos[2]= {0,0};
static uint16_t fifoBuffer[FIFOMAX];
static uint16_t fifoPos = 0;
#endif

// start from tools/sdk/include/soc/soc/i2c_struct.h

typedef union {
    struct {
        uint32_t byte_num:      8;              /*Byte_num represent the number of data need to be send or data need to be received.*/
        uint32_t ack_en:        1;              /*ack_check_en  ack_exp and ack value are used to control  the ack bit.*/
        uint32_t ack_exp:       1;              /*ack_check_en  ack_exp and ack value are used to control  the ack bit.*/
        uint32_t ack_val:       1;              /*ack_check_en  ack_exp and ack value are used to control  the ack bit.*/
        uint32_t op_code:       3;              /*op_code is the command  0：RSTART   1：WRITE  2：READ  3：STOP . 4:END.*/
        uint32_t reserved14:   17;
        uint32_t done:  1;                      /*When command0 is done in I2C Master mode  this bit changes to high level.*/
    };
    uint32_t val;
} I2C_COMMAND_t;

typedef union {
    struct {
        uint32_t rx_fifo_full_thrhd: 5;
        uint32_t tx_fifo_empty_thrhd:5;         //Config tx_fifo empty threhd value when using apb fifo access * /
        uint32_t nonfifo_en:         1;         //Set this bit to enble apb nonfifo access. * /
        uint32_t fifo_addr_cfg_en:   1;         //When this bit is set to 1 then the byte after address represent the offset address of I2C Slave's ram. * /
        uint32_t rx_fifo_rst:        1;         //Set this bit to reset rx fifo when using apb fifo access. * /
        // chuck while this bit is 1, the RX fifo is held in REST, Toggle it * /
        uint32_t tx_fifo_rst:        1;         //Set this bit to reset tx fifo when using apb fifo access. * /
        // chuck while this bit is 1, the TX fifo is held in REST, Toggle it * /
        uint32_t nonfifo_rx_thres:   6;         //when I2C receives more than nonfifo_rx_thres data  it will produce rx_send_full_int_raw interrupt and update the current offset address of the receiving data.* /
        uint32_t nonfifo_tx_thres:   6;         //when I2C sends more than nonfifo_tx_thres data  it will produce tx_send_empty_int_raw interrupt and update the current offset address of the sending data. * /
        uint32_t reserved26:         6;
    };
    uint32_t val;
} I2C_FIFO_CONF_t;

typedef union {
        struct {
            uint32_t rx_fifo_start_addr: 5;         /*This is the offset address of the last receiving data as described in nonfifo_rx_thres_register.*/
            uint32_t rx_fifo_end_addr:   5;         /*This is the offset address of the first receiving data as described in nonfifo_rx_thres_register.*/
            uint32_t tx_fifo_start_addr: 5;         /*This is the offset address of the first  sending data as described in nonfifo_tx_thres register.*/
            uint32_t tx_fifo_end_addr:   5;         /*This is the offset address of the last  sending data as described in nonfifo_tx_thres register.*/
            uint32_t reserved20:        12;
        };
        uint32_t val;
    } I2C_FIFO_ST_t;
   
// end from tools/sdk/include/soc/soc/i2c_struct.h

// sync between dispatch(i2cProcQueue) and worker(i2c_isr_handler_default)
typedef enum {
    //I2C_NONE=0,
    I2C_STARTUP=1,
    I2C_RUNNING,
    I2C_DONE
} I2C_STAGE_t;

typedef enum {
    I2C_NONE=0,
    I2C_MASTER,
    I2C_SLAVE,
    I2C_MASTERSLAVE
} I2C_MODE_t;

// internal Error condition
typedef enum {
    //  I2C_NONE=0,
    I2C_OK=1,
    I2C_ERROR,
    I2C_ADDR_NAK,
    I2C_DATA_NAK,
    I2C_ARBITRATION,
    I2C_TIMEOUT
} I2C_ERROR_t;

// i2c_event bits for EVENTGROUP bits
// needed to minimize change events, FreeRTOS Daemon overload, so ISR will only set values
// on Exit.  Dispatcher will set bits for each dq before/after ISR completion
#define EVENT_ERROR_NAK (BIT(0))
#define EVENT_ERROR     (BIT(1))
#define EVENT_ERROR_BUS_BUSY  (BIT(2))
#define EVENT_RUNNING   (BIT(3))
#define EVENT_DONE      (BIT(4))
#define EVENT_IN_END    (BIT(5))
#define EVENT_ERROR_PREV  (BIT(6))
#define EVENT_ERROR_TIMEOUT   (BIT(7))
#define EVENT_ERROR_ARBITRATION (BIT(8))
#define EVENT_ERROR_DATA_NAK  (BIT(9))
#define EVENT_MASK 0x3F

// control record for each dq entry
typedef union {
    struct {
        uint32_t  addr: 16; // I2C address, if 10bit must have 0x7800 mask applied, else 8bit
        uint32_t  mode:         1; // transaction direction 0 write, 1 read
        uint32_t  stop:         1; // sendStop 0 no, 1 yes
        uint32_t  startCmdSent: 1; // START cmd has been added to command[]
        uint32_t  addrCmdSent:  1; // addr WRITE cmd has been added to command[]
        uint32_t  dataCmdSent:  1; // all necessary DATA(READ/WRITE) cmds added to command[]
        uint32_t  stopCmdSent:  1; // completed all necessary commands
        uint32_t  addrReq:      2; // number of addr bytes need to send address
        uint32_t  addrSent:     2; // number of addr bytes added to FIFO
        uint32_t  reserved_31:  6;
    };
    uint32_t val;
} I2C_DATA_CTRL_t;

// individual dq element
typedef struct {
    uint8_t *data;           // data pointer for read/write buffer
    uint16_t length;         // size of data buffer
    uint16_t position;       // current position for next char in buffer (<length)
    uint16_t cmdBytesNeeded; // used to control number of I2C_COMMAND_t blocks added to queue
    I2C_DATA_CTRL_t ctrl;
    EventGroupHandle_t queueEvent;  // optional user supplied for Async feedback EventBits
} I2C_DATA_QUEUE_t;

struct i2c_struct_t {
    i2c_dev_t * dev;
#if !CONFIG_DISABLE_HAL_LOCKS
    xSemaphoreHandle lock;
#endif
    uint8_t num;
    int8_t sda;
    int8_t scl;
    I2C_MODE_t mode;
    I2C_STAGE_t stage;
    I2C_ERROR_t error;
    EventGroupHandle_t i2c_event; // a way to monitor ISR process
    // maybe use it to trigger callback for OnRequest()
    intr_handle_t intr_handle;       /*!< I2C interrupt handle*/
    I2C_DATA_QUEUE_t * dq;
    uint16_t queueCount; // number of dq entries in queue.
    uint16_t queuePos; // current queue that still has or needs data (out/in)
    int16_t  errorByteCnt;  // byte pos where error happened, -1 devId, 0..(length-1) data
    uint16_t errorQueue; // errorByteCnt is in this queue,(for error locus)
    uint32_t exitCode;
    uint32_t debugFlags;
};

enum {
    I2C_CMD_RSTART,
    I2C_CMD_WRITE,
    I2C_CMD_READ,
    I2C_CMD_STOP,
    I2C_CMD_END
};

#if CONFIG_DISABLE_HAL_LOCKS
#define I2C_MUTEX_LOCK()
#define I2C_MUTEX_UNLOCK()

static i2c_t _i2c_bus_array[2] = {
    {(volatile i2c_dev_t *)(DR_REG_I2C_EXT_BASE_FIXED), 0, -1, -1,I2C_NONE,I2C_NONE,I2C_ERROR_OK,NULL,NULL,NULL,0,0,0,0,0},
    {(volatile i2c_dev_t *)(DR_REG_I2C1_EXT_BASE_FIXED), 1, -1, -1,I2C_NONE,I2C_NONE,I2C_ERROR_OK,NULL,NULL,NULL,0,0,0,0,0}
};
#else
#define I2C_MUTEX_LOCK()    do {} while (xSemaphoreTakeRecursive(i2c->lock, portMAX_DELAY) != pdPASS)
#define I2C_MUTEX_UNLOCK()  xSemaphoreGiveRecursive(i2c->lock)

static i2c_t _i2c_bus_array[2] = {
    {(volatile i2c_dev_t *)(DR_REG_I2C_EXT_BASE_FIXED), NULL, 0, -1, -1, I2C_NONE,I2C_NONE,I2C_ERROR_OK,NULL,NULL,NULL,0,0,0,0,0,0},
    {(volatile i2c_dev_t *)(DR_REG_I2C1_EXT_BASE_FIXED), NULL, 1, -1, -1,I2C_NONE,I2C_NONE,I2C_ERROR_OK,NULL,NULL,NULL,0,0,0,0,0,0}
};
#endif

/*
 * index     - command index (0 to 15)
 * op_code   - is the command
 * byte_num  - This register is to store the amounts of data that is read and written. byte_num in RSTART, STOP, END is null.
 * ack_val   - Each data byte is terminated by an ACK bit used to set the bit level.
 * ack_exp   - This bit is to set an expected ACK value for the transmitter.
 * ack_check - This bit is to decide whether the transmitter checks ACK bit. 1 means yes and 0 means no.
 * */


/* Stickbreaker ISR mode debug support
 */
static void IRAM_ATTR i2cDumpCmdQueue(i2c_t *i2c)
{
#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_ERROR)&&(defined ENABLE_I2C_DEBUG_BUFFER)
    static const char * const cmdName[] ={"RSTART","WRITE","READ","STOP","END"};
    uint8_t i=0;
    while(i<16) {
        I2C_COMMAND_t c;
        c.val=i2c->dev->command[i].val;
        log_e("[%2d]\t%c\t%s\tval[%d]\texp[%d]\ten[%d]\tbytes[%d]",i,(c.done?'Y':'N'),
              cmdName[c.op_code],
              c.ack_val,
              c.ack_exp,
              c.ack_en,
              c.byte_num);
        i++;
    }
#endif
}

/* Stickbreaker ISR mode debug support
 */
#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO)
static void i2cDumpDqData(i2c_t * i2c)
{
#if defined (ENABLE_I2C_DEBUG_BUFFER)
    uint16_t a=0;
    char buff[140];
    I2C_DATA_QUEUE_t *tdq;
    int digits=0,lenDigits=0;
    a = i2c->queueCount;
    while(a>0) {
        digits++;
        a /= 10;
    }
    while(a<i2c->queueCount) { // find maximum number of len decimal digits for formatting
        if (i2c->dq[a].length > lenDigits ) lenDigits = i2c->dq[a].length;
        a++;
    }
    a=0;
    while(lenDigits>0){
      a++;
      lenDigits /= 10;
    }
    lenDigits = a;
    a = 0;
    while(a<i2c->queueCount) {
        tdq=&i2c->dq[a];
        char buf1[10],buf2[10];
        sprintf(buf1,"%0*d",lenDigits,tdq->length);
        sprintf(buf2,"%0*d",lenDigits,tdq->position);
        log_i("[%0*d] %sbit %x %c %s buf@=%p, len=%s, pos=%s, ctrl=%d%d%d%d%d",digits,a,
        (tdq->ctrl.addr>0x100)?"10":"7",
        (tdq->ctrl.addr>0x100)?(((tdq->ctrl.addr&0x600)>>1)|(tdq->ctrl.addr&0xff)):(tdq->ctrl.addr>>1),
        (tdq->ctrl.mode)?'R':'W',
        (tdq->ctrl.stop)?"STOP":"",
        tdq->data,
        buf1,buf2,
        tdq->ctrl.startCmdSent,tdq->ctrl.addrCmdSent,tdq->ctrl.dataCmdSent,(tdq->ctrl.stop)?tdq->ctrl.stopCmdSent:0,tdq->ctrl.addrSent
        );
        uint16_t offset = 0;
        while(offset<tdq->length) {
            memset(buff,' ',140);
            buff[139]='\0';
            uint16_t i = 0,j;
            j=sprintf(buff,"0x%04x: ",offset);
            while((i<32)&&(offset < tdq->length)) {
                char ch = tdq->data[offset];
                sprintf((char*)&buff[(i*3)+41],"%02x ",ch);
                if((ch<32)||(ch>126)) {
                    ch='.';
                }
                j+=sprintf((char*)&buff[j],"%c",ch);
                buff[j]=' ';
                i++;
                offset++;
            }
            log_i("%s",buff);
        }
        a++;
    }
#else
    log_i("Debug Buffer not Enabled");
#endif
}
#endif
#if ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO
static void i2cDumpI2c(i2c_t * i2c)
{
    log_e("i2c=%p",i2c);
    log_i("dev=%p date=%p",i2c->dev,i2c->dev->date);
#if !CONFIG_DISABLE_HAL_LOCKS
    log_i("lock=%p",i2c->lock);
#endif
    log_i("num=%d",i2c->num);
    log_i("mode=%d",i2c->mode);
    log_i("stage=%d",i2c->stage);
    log_i("error=%d",i2c->error);
    log_i("event=%p bits=%x",i2c->i2c_event,(i2c->i2c_event)?xEventGroupGetBits(i2c->i2c_event):0);
    log_i("intr_handle=%p",i2c->intr_handle);
    log_i("dq=%p",i2c->dq);
    log_i("queueCount=%d",i2c->queueCount);
    log_i("queuePos=%d",i2c->queuePos);
    log_i("errorByteCnt=%d",i2c->errorByteCnt);
    log_i("errorQueue=%d",i2c->errorQueue);
    log_i("debugFlags=0x%08X",i2c->debugFlags);
    if(i2c->dq) {
        i2cDumpDqData(i2c);
    }
}
#endif

#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO)  
static void i2cDumpInts(uint8_t num)
{
#if defined (ENABLE_I2C_DEBUG_BUFFER)
    uint32_t b;
    log_i("%u row\tcount\tINTR\tTX\tRX\tTick ",num);
    for(uint32_t a=1; a<=INTBUFFMAX; a++) {
        b=(a+intPos[num])%INTBUFFMAX;
        if(intBuff[b][0][num]!=0) {
            log_i("[%02d]\t0x%04x\t0x%04x\t0x%04x\t0x%04x\t0x%08x",b,((intBuff[b][0][num]>>16)&0xFFFF),(intBuff[b][0][num]&0xFFFF),((intBuff[b][1][num]>>16)&0xFFFF),(intBuff[b][1][num]&0xFFFF),intBuff[b][2][num]);
        }
    }
#else
    log_i("Debug Buffer not Enabled");
#endif
}
#endif

#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO)&&(defined ENABLE_I2C_DEBUG_BUFFER)
static void IRAM_ATTR i2cDumpStatus(i2c_t * i2c){
    typedef union {
        struct {
            uint32_t ack_rec:             1;        /*This register stores the value of ACK bit.*/
            uint32_t slave_rw:            1;        /*when in slave mode  1：master read slave  0: master write slave.*/
            uint32_t time_out:            1;        /*when I2C takes more than time_out_reg clocks to receive a data then this register changes to high level.*/
            uint32_t arb_lost:            1;        /*when I2C lost control of SDA line  this register changes to high level.*/
            uint32_t bus_busy:            1;        /*1:I2C bus is busy transferring data. 0:I2C bus is in idle state.*/
            uint32_t slave_addressed:     1;        /*when configured as i2c slave  and the address send by master is equal to slave's address  then this bit will be high level.*/
            uint32_t byte_trans:          1;        /*This register changes to high level when one byte is transferred.*/
            uint32_t reserved7:           1;
            uint32_t rx_fifo_cnt:         6;        /*This register represent the amount of data need to send.*/
            uint32_t reserved14:          4;
            uint32_t tx_fifo_cnt:         6;        /*This register stores the amount of received data  in ram.*/
            uint32_t scl_main_state_last: 3;        /*This register stores the value of state machine for i2c module.  3'h0: SCL_MAIN_IDLE  3'h1: SCL_ADDRESS_SHIFT 3'h2: SCL_ACK_ADDRESS  3'h3: SCL_RX_DATA  3'h4 SCL_TX_DATA  3'h5:SCL_SEND_ACK 3'h6:SCL_WAIT_ACK*/
            uint32_t reserved27:          1;
            uint32_t scl_state_last:      3;        /*This register stores the value of state machine to produce SCL. 3'h0: SCL_IDLE  3'h1:SCL_START   3'h2:SCL_LOW_EDGE  3'h3: SCL_LOW   3'h4:SCL_HIGH_EDGE   3'h5:SCL_HIGH  3'h6:SCL_STOP*/
            uint32_t reserved31:          1;
        };
        uint32_t val;
    } status_reg;
     
    status_reg sr;
    sr.val= i2c->dev->status_reg.val;
    
    log_i("ack(%d) sl_rw(%d) to(%d) arb(%d) busy(%d) sl(%d) trans(%d) rx(%d) tx(%d) sclMain(%d) scl(%d)",sr.ack_rec,sr.slave_rw,sr.time_out,sr.arb_lost,sr.bus_busy,sr.slave_addressed,sr.byte_trans, sr.rx_fifo_cnt, sr.tx_fifo_cnt,sr.scl_main_state_last, sr.scl_state_last);
}
#endif

#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO)&&(defined ENABLE_I2C_DEBUG_BUFFER)
static void i2cDumpFifo(i2c_t * i2c){
char buf[64];
uint16_t k = 0;
uint16_t i = fifoPos+1;
  i %=FIFOMAX;
while((fifoBuffer[i]==0)&&(i!=fifoPos)){
  i++;
  i %=FIFOMAX;
}
if(i != fifoPos){// actual data
    do{
      if(fifoBuffer[i] & 0x8000){ // address byte
        if(fifoBuffer[i] & 0x100) { // read
          if(fifoBuffer[i] & 0x1) { // valid read dev id
            k+= sprintf(&buf[k],"READ  0x%02X",(fifoBuffer[i]&0xff)>>1);
          } else { // invalid read dev id
            k+= sprintf(&buf[k],"Bad READ  0x%02X",(fifoBuffer[i]&0xff));
          }
        } else { // write
          if(fifoBuffer[i] & 0x1) { // bad write dev id
            k+= sprintf(&buf[k],"bad WRITE 0x%02X",(fifoBuffer[i]&0xff));
          } else { // good Write
            k+= sprintf(&buf[k],"WRITE 0x%02X",(fifoBuffer[i]&0xff)>>1);
          }
        }
      } else k += sprintf(&buf[k],"% 4X ",fifoBuffer[i]);

      i++;
      i %= FIFOMAX;
      bool outBuffer=false;
      if( fifoBuffer[i] & 0x8000){
        outBuffer=true;
        k=0;
      }
      if((outBuffer)||(k>50)||(i==fifoPos)) log_i("%s",buf);
      outBuffer = false;
      if(k>50) {
        k=sprintf(buf,"-> ");
      }
    }while( i!= fifoPos);
}
}
#endif

static void IRAM_ATTR i2cTriggerDumps(i2c_t * i2c, uint8_t trigger, const char locus[]){
#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO)&&(defined ENABLE_I2C_DEBUG_BUFFER)
    if( trigger ){
      log_i("%s",locus);      
      if(trigger & 1) i2cDumpI2c(i2c);
      if(trigger & 2) i2cDumpInts(i2c->num);
      if(trigger & 4) i2cDumpCmdQueue(i2c);
      if(trigger & 8) i2cDumpStatus(i2c);
      if(trigger & 16) i2cDumpFifo(i2c);
    }
#endif    
}
 // end of debug support routines
 
/* Start of CPU Clock change Support
*/

static void i2cApbChangeCallback(void * arg, apb_change_ev_t ev_type, uint32_t old_apb, uint32_t new_apb){
    i2c_t* i2c = (i2c_t*) arg; // recover data
    if(i2c == NULL) {  // point to peripheral control block does not exits
        return;
    }
    uint32_t oldFreq=0;
    switch(ev_type){
        case APB_BEFORE_CHANGE : 
            if(new_apb < 3000000) {// too slow
                log_e("apb speed %d too slow",new_apb);
                break;
            }
            I2C_MUTEX_LOCK(); // lock will spin until current transaction is completed
            break;
        case APB_AFTER_CHANGE :
            oldFreq = (i2c->dev->scl_low_period.period+i2c->dev->scl_high_period.period); //read old apbCycles 
            if(oldFreq>0) { // was configured with value
                oldFreq = old_apb / oldFreq;
                i2cSetFrequency(i2c,oldFreq);
            }
            I2C_MUTEX_UNLOCK();
            break;
        default : 
            log_e("unk ev %u",ev_type);
            I2C_MUTEX_UNLOCK();
    }
    return;
}
/* End of CPU Clock change Support
*/ 
static void IRAM_ATTR i2cSetCmd(i2c_t * i2c, uint8_t index, uint8_t op_code, uint8_t byte_num, bool ack_val, bool ack_exp, bool ack_check)
{
    I2C_COMMAND_t cmd;
    cmd.val=0;
    cmd.ack_en = ack_check;
    cmd.ack_exp = ack_exp;
    cmd.ack_val = ack_val;
    cmd.byte_num = byte_num;
    cmd.op_code = op_code;
    i2c->dev->command[index].val = cmd.val;
}
 

static void IRAM_ATTR fillCmdQueue(i2c_t * i2c, bool INTS)
{
    /* this function is called on initial i2cProcQueue() or when a I2C_END_DETECT_INT occurs
     */
    uint16_t cmdIdx = 0;
    uint16_t qp = i2c->queuePos; // all queues before queuePos have been completely processed,
      // so look start by checking the 'current queue' so see if it needs commands added to
      // hardware peripheral command list. walk through each queue entry until all queues have been
      // checked
    bool done;
    bool needMoreCmds = false;
    bool ena_rx=false; // if we add a read op, better enable Rx_Fifo IRQ
    bool ena_tx=false; // if we add a Write op, better enable TX_Fifo IRQ

    while(!needMoreCmds&&(qp < i2c->queueCount)) { // check if more possible cmds
        if(i2c->dq[qp].ctrl.stopCmdSent) {// marks that all required cmds[] have been added to peripheral 
            qp++;
        } else {
            needMoreCmds=true;
        }
    }
    //log_e("needMoreCmds=%d",needMoreCmds);
    done=(!needMoreCmds)||(cmdIdx>14);

    while(!done) { // fill the command[] until either 0..14 filled or out of cmds and last cmd is STOP
        //CMD START
        I2C_DATA_QUEUE_t *tdq=&i2c->dq[qp]; // simpler coding

        if((!tdq->ctrl.startCmdSent) && (cmdIdx < 14)) { // has this dq element's START command been added?
            // (cmdIdx<14)  because a START op cannot directly precede an END op, else a time out cascade occurs
            i2cSetCmd(i2c, cmdIdx++, I2C_CMD_RSTART, 0, false, false, false);
            tdq->ctrl.startCmdSent=1;
        }

        //CMD WRITE ADDRESS
        if((!done)&&(tdq->ctrl.startCmdSent)) { // have to leave room for continue(END), and START must have been sent!
            if(!tdq->ctrl.addrCmdSent) {
                i2cSetCmd(i2c, cmdIdx++, I2C_CMD_WRITE, tdq->ctrl.addrReq, false, false, true); //load address in cmdlist, validate (low) ack
                tdq->ctrl.addrCmdSent=1;
                done =(cmdIdx>14);
                ena_tx=true; // tx Data necessary
            }
        }

        /* Can I have another Sir?
        ALL CMD queues must be terminated with either END or STOP.

        If END is used, when refilling the cmd[] next time, no entries from END to [15] can be used.
        AND the cmd[] must be filled starting at [0] with commands. Either fill all 15 [0]..[14] and leave the
        END in [15] or include a STOP in one of the positions [0]..[14].  Any entries after a STOP are IGNORED by the StateMachine.
        The END operation does not complete until ctr->trans_start=1 has been issued.

        So, only refill from [0]..[14], leave [15] for a continuation(END) if necessary.
        As a corollary, once END exists in [15], you do not need to overwrite it for the
        next continuation. It is never modified. But, I update it every time because it might
        actually be the first time!

        23NOV17  START cannot proceed END.  if START is in[14], END cannot be in [15].
        So, if END is moved to [14], [14] and [15] can no longer be used for anything other than END.
        If a START is found in [14] then a prior READ or WRITE must be expanded so that there is no START element in [14].
         */

         if((!done)&&(tdq->ctrl.addrCmdSent)) { //room in command[] for at least One data (read/Write) cmd
            uint8_t blkSize=0; // max is 255
            while(( tdq->cmdBytesNeeded > tdq->ctrl.mode )&&(!done )) { // more bytes needed and room in cmd queue, leave room for END
                blkSize = (tdq->cmdBytesNeeded > 255)?255:(tdq->cmdBytesNeeded - tdq->ctrl.mode); // Last read cmd needs different ACK setting, so leave 1 byte remainder on reads
                tdq->cmdBytesNeeded -= blkSize; 
                if(tdq->ctrl.mode==1) { //read mode
                    i2cSetCmd(i2c, (cmdIdx)++, I2C_CMD_READ, blkSize,false,false,false); // read    cmd, this can't be the last read.
                    ena_rx=true; // need to enable rxFifo IRQ
                } else { // write
                    i2cSetCmd(i2c, cmdIdx++, I2C_CMD_WRITE, blkSize, false, false, true); // check for Nak
                    ena_tx=true; // need to enable txFifo IRQ
                }
                done = cmdIdx>14; //have to leave room for END
            }

            if(!done) { // buffer is not filled completely
                if((tdq->ctrl.mode==1)&&(tdq->cmdBytesNeeded==1)) { //special last read byte NAK
                    i2cSetCmd(i2c, (cmdIdx)++, I2C_CMD_READ, 1,true,false,false);
                    // send NAK to mark end of read
                    tdq->cmdBytesNeeded=0;
                    done = cmdIdx > 14;
                    ena_rx=true;
                }
            }

            tdq->ctrl.dataCmdSent=(tdq->cmdBytesNeeded==0); // enough command[] to send all data

            if((!done)&&(tdq->ctrl.dataCmdSent)) { // possibly add stop
                if(!tdq->ctrl.stopCmdSent){
                    if(tdq->ctrl.stop) { //send a stop
                        i2cSetCmd(i2c, (cmdIdx)++,I2C_CMD_STOP,0,false,false,false);
                        done = cmdIdx > 14;
                    }
                    tdq->ctrl.stopCmdSent = 1;
                }
            }
        }

        if((cmdIdx==14)&&(!tdq->ctrl.startCmdSent)) {
            // START would have preceded END, causes SM TIMEOUT
            // need to stretch out a prior WRITE or READ to two Command[] elements
            done = false; // reuse it
            uint16_t i = 13; // start working back until a READ/WRITE has >1 numBytes
            cmdIdx =15;
            while(!done) {
                i2c->dev->command[i+1].val = i2c->dev->command[i].val; // push it down
                if (((i2c->dev->command[i].op_code == 1)||(i2c->dev->command[i].op_code==2))) {
                    /* add a dummy read/write cmd[] with num_bytes set to zero,just a place holder in the cmd[]list
                     */
                    i2c->dev->command[i].byte_num = 0;
                    done = true;

                } else {
                    if(i > 0) {
                        i--;
                    } else { // unable to stretch, fatal
                        log_e("invalid CMD[] layout Stretch Failed");
                        i2cDumpCmdQueue(i2c);
                        done = true;
                    }
                }
            }

        }


        if(cmdIdx==15) { //need continuation, even if STOP is in 14, it will not matter
            // cmd buffer is almost full, Add END as a continuation feature
            i2cSetCmd(i2c, (cmdIdx)++,I2C_CMD_END, 0,false,false,false);
            i2c->dev->int_ena.end_detect=1; 
            i2c->dev->int_clr.end_detect=1; 
            done = true;
        }

        if(!done) {
            if(tdq->ctrl.stopCmdSent) { // this queue element has been completely added to command[] buffer
                qp++;
                if(qp < i2c->queueCount) {
                    tdq = &i2c->dq[qp];
                } else {
                    done = true;
                }
            }
        }

    }// while(!done)
    if(INTS) { // don't want to prematurely enable fifo ints until ISR is ready to handle them.
        if(ena_rx) {
            i2c->dev->int_ena.rx_fifo_full = 1;
        }
        if(ena_tx) {
            i2c->dev->int_ena.tx_fifo_empty = 1;
        }
    }
}

static void IRAM_ATTR fillTxFifo(i2c_t * i2c)
{
    /*
    12/01/2017 The Fifo's are independent, 32 bytes of tx and 32 bytes of Rx.
    overlap is not an issue, just keep them full/empty the status_reg.xx_fifo_cnt
    tells the truth. And the INT's fire correctly
     */
    uint16_t a=i2c->queuePos; // currently executing dq,
    bool full=!(i2c->dev->status_reg.tx_fifo_cnt<31);
    uint8_t cnt;
    bool rxQueueEncountered = false;
    while((a < i2c->queueCount) && !full) {
        I2C_DATA_QUEUE_t *tdq = &i2c->dq[a];
        cnt=0;
        // add to address to fifo ctrl.addr already has R/W bit positioned correctly
        if(tdq->ctrl.addrSent < tdq->ctrl.addrReq) { // need to send address bytes
            if(tdq->ctrl.addrReq==2) { //10bit
                if(tdq->ctrl.addrSent==0) { //10bit highbyte needs sent
                    if(!full) { // room in fifo
                        i2c->dev->fifo_data.val = ((tdq->ctrl.addr>>8)&0xFF);
                        cnt++;
                        tdq->ctrl.addrSent=1; //10bit highbyte sent
                    }
                }
                full=!(i2c->dev->status_reg.tx_fifo_cnt<31);

                if(tdq->ctrl.addrSent==1) { //10bit Lowbyte needs sent
                    if(!full) { // room in fifo
                        i2c->dev->fifo_data.val = tdq->ctrl.addr&0xFF;
                        cnt++;
                        tdq->ctrl.addrSent=2; //10bit lowbyte sent
                    }
                }
            } else { // 7bit}
                if(tdq->ctrl.addrSent==0) { // 7bit Lowbyte needs sent
                    if(!full) { // room in fifo
                        i2c->dev->fifo_data.val = tdq->ctrl.addr&0xFF;
                        cnt++;
                        tdq->ctrl.addrSent=1; // 7bit lowbyte sent
#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO) && (defined ENABLE_I2C_DEBUG_BUFFER)
                        uint16_t a = 0x8000 | tdq->ctrl.addr | (tdq->ctrl.mode<<8);
                        fifoBuffer[fifoPos++] = a;
                        fifoPos %= FIFOMAX;
#endif
                    }
                }
            }
        }
        // add write data to fifo
        if(tdq->ctrl.mode==0) { // write
            if(tdq->ctrl.addrSent == tdq->ctrl.addrReq) { //address has been sent, is Write Mode!
                uint32_t moveCnt = 32 - i2c->dev->status_reg.tx_fifo_cnt; // how much room in txFifo?
                while(( moveCnt>0)&&(tdq->position < tdq->length)) {
#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO) && (defined ENABLE_I2C_DEBUG_BUFFER)
                    fifoBuffer[fifoPos++] =  tdq->data[tdq->position];
                    fifoPos %= FIFOMAX;
#endif
                    i2c->dev->fifo_data.val = tdq->data[tdq->position++];
                    cnt++;
                    moveCnt--;

                }
            }
        } else { // read Queue Encountered, can't update QueuePos past this point, emptyRxfifo will do it
            if( ! rxQueueEncountered ) {
              rxQueueEncountered = true;
              if(a > i2c->queuePos){
                i2c->queuePos = a; 
              }
           }              
        }
#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO) && (defined ENABLE_I2C_DEBUG_BUFFER)

        // update debug buffer tx counts
        cnt += intBuff[intPos[i2c->num]][1][i2c->num]>>16;
        intBuff[intPos[i2c->num]][1][i2c->num] = (intBuff[intPos[i2c->num]][1][i2c->num]&0xFFFF)|(cnt<<16);

#endif
        full=!(i2c->dev->status_reg.tx_fifo_cnt<31);
        if(!full) {
            a++;    // check next buffer for address tx, or write data
        }
    }

    if(a >= i2c->queueCount ) { // disable TX IRQ, all tx Data has been queued
        i2c->dev->int_ena.tx_fifo_empty= 0;
    }

    i2c->dev->int_clr.tx_fifo_empty=1;
}


static void IRAM_ATTR emptyRxFifo(i2c_t * i2c)
{
    uint32_t d, cnt=0, moveCnt;
    
    moveCnt = i2c->dev->status_reg.rx_fifo_cnt;//no need to check the reg until this many are read

    while((moveCnt > 0)&&(i2c->queuePos < i2c->queueCount)){ // data to move    

        I2C_DATA_QUEUE_t *tdq =&i2c->dq[i2c->queuePos]; //short cut

        while((tdq->position >= tdq->length)&&( i2c->queuePos < i2c->queueCount)){ // find were to store
            i2c->queuePos++;
            tdq = &i2c->dq[i2c->queuePos];
        }
      
        if(i2c->queuePos >= i2c->queueCount){ // bad stuff, rx data but no place to put it!
            log_e("no Storage location for %d",moveCnt);
        // discard
            while(moveCnt>0){
                d = i2c->dev->fifo_data.val;
                moveCnt--;
                cnt++;
            }
            break;
        }
        
        if(tdq->ctrl.mode == 1){ // read command
            if(moveCnt > (tdq->length - tdq->position)) { //make sure they go in this dq
        // part of these reads go into the next dq
                moveCnt = (tdq->length - tdq->position);
            }
        } else {// error
            log_e("RxEmpty(%d) call on TxBuffer? dq=%d",moveCnt,i2c->queuePos);
        // discard
            while(moveCnt>0){
                d = i2c->dev->fifo_data.val;
                moveCnt--;
                cnt++;
            }
            break;
        }

        while(moveCnt > 0) { // store data
            d = i2c->dev->fifo_data.val;
            moveCnt--;
            cnt++;
            tdq->data[tdq->position++] = (d&0xFF);
        }

        moveCnt = i2c->dev->status_reg.rx_fifo_cnt; //any more out there?
    }
    
#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO)&& (defined ENABLE_I2C_DEBUG_BUFFER)
        // update Debug rxCount
        cnt += (intBuff[intPos[i2c->num]][1][i2c->num])&0xffFF;
        intBuff[intPos[i2c->num]][1][i2c->num] = (intBuff[intPos[i2c->num]][1][i2c->num]&0xFFFF0000)|cnt;
#endif
}

static void IRAM_ATTR i2cIsrExit(i2c_t * i2c,const uint32_t eventCode,bool Fatal)
{

    switch(eventCode) {
    case EVENT_DONE:
        i2c->error = I2C_OK;
        break;
    case EVENT_ERROR_NAK :
        i2c->error =I2C_ADDR_NAK;
        break;
    case EVENT_ERROR_DATA_NAK :
        i2c->error =I2C_DATA_NAK;
        break;
    case EVENT_ERROR_TIMEOUT :
        i2c->error = I2C_TIMEOUT;
        break;
    case EVENT_ERROR_ARBITRATION:
        i2c->error = I2C_ARBITRATION;
        break;
    default :
        i2c->error = I2C_ERROR;
    }
    uint32_t exitCode = EVENT_DONE | eventCode |(Fatal?EVENT_ERROR:0);
    if((i2c->queuePos < i2c->queueCount) && (i2c->dq[i2c->queuePos].ctrl.mode == 1)) {
        emptyRxFifo(i2c);    // grab last few characters
    }
    i2c->dev->int_ena.val = 0; // shut down interrupts
    i2c->dev->int_clr.val = 0x1FFF;
    i2c->stage = I2C_DONE;
    i2c->exitCode = exitCode; //true eventcode

    portBASE_TYPE HPTaskAwoken = pdFALSE,xResult;
    // try to notify Dispatch we are done,
    // else the 50ms time out will recover the APP, just a little slower
    HPTaskAwoken = pdFALSE;
    xResult = xEventGroupSetBitsFromISR(i2c->i2c_event, exitCode, &HPTaskAwoken);
    if(xResult == pdPASS) {
        if(HPTaskAwoken==pdTRUE) {
            portYIELD_FROM_ISR();
            //      log_e("Yield to Higher");
        }
    }

}

static void IRAM_ATTR i2c_update_error_byte_cnt(i2c_t * i2c)
{
/* i2c_update_error_byte_cnt 07/18/2018
  Only called after an error has occurred, so, most of the time this function is never used.
  This function obliterates the need to interrupt monitor each byte transferred, at high bitrates
  the byte interrupts were overwhelming the OS.  Spurious Interrupts were being generated.
  it updates errorByteCnt, errorQueue. 
 */
    uint16_t a=0; // start at top of DQ, count how many bytes added to tx fifo, and received from rx_fifo.
    int16_t bc = 0;
    I2C_DATA_QUEUE_t *tdq;
    i2c->errorByteCnt = 0; 
    while( a < i2c->queueCount){ // add up all bytes loaded into fifo's
        tdq = &i2c->dq[a];
        i2c->errorByteCnt += tdq->ctrl.addrSent;
        i2c->errorByteCnt += tdq->position; 
        a++;
    }
  // now errorByteCnt contains total bytes moved into and out of FIFO's
  // but, there may still be bytes waiting in Fifo's
    i2c->errorByteCnt -= i2c->dev->status_reg.tx_fifo_cnt; // waiting to go out;
    i2c->errorByteCnt += i2c->dev->status_reg.rx_fifo_cnt; // already received
// now walk thru DQ again, find which byte is 'current'
    bc = i2c->errorByteCnt;
    i2c->errorQueue = 0;
    while( i2c->errorQueue < i2c->queueCount ){
        tdq = &i2c->dq[i2c->errorQueue];
        if(bc>0){ // not found yet
            if( tdq->ctrl.addrSent >= bc){ // in address
                bc = -1; // in address
                break;
            } else {
                bc -= tdq->ctrl.addrSent;
                if( tdq->length > bc) { // data nak
                    break;
                } else { // count down
                    bc -= tdq->length;
                }
            }
        } else break;
        
        i2c->errorQueue++;
    }  
  
    i2c->errorByteCnt = bc;
 }

static void IRAM_ATTR i2c_isr_handler_default(void* arg)
{
    i2c_t* p_i2c = (i2c_t*) arg; // recover data
    uint32_t activeInt = p_i2c->dev->int_status.val&0x7FF;

    if(p_i2c->stage==I2C_DONE) { //get Out, can't service, not configured
        p_i2c->dev->int_ena.val = 0;
        p_i2c->dev->int_clr.val = 0x1FFF;
#if ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_VERBOSE
        uint32_t raw = p_i2c->dev->int_raw.val;
        log_w("eject raw=%p, int=%p",raw,activeInt);
#endif
        return;
    }
    while (activeInt != 0) { // Ordering of 'if(activeInt)' statements is important, don't change

    #if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO) && (defined ENABLE_I2C_DEBUG_BUFFER)
        if(activeInt==(intBuff[intPos[p_i2c->num]][0][p_i2c->num]&0x1fff)) {
            intBuff[intPos[p_i2c->num]][0][p_i2c->num] = (((intBuff[intPos[p_i2c->num]][0][p_i2c->num]>>16)+1)<<16)|activeInt;
        } else {
            intPos[p_i2c->num]++;
            intPos[p_i2c->num] %= INTBUFFMAX;
            intBuff[intPos[p_i2c->num]][0][p_i2c->num] = (1<<16) | activeInt;
            intBuff[intPos[p_i2c->num]][1][p_i2c->num] = 0;
        }

        intBuff[intPos[p_i2c->num]][2][p_i2c->num] = xTaskGetTickCountFromISR(); // when IRQ fired

#endif
 
        if (activeInt & I2C_TRANS_START_INT_ST_M) {
            if(p_i2c->stage==I2C_STARTUP) {
                p_i2c->stage=I2C_RUNNING;
            }

            activeInt &=~I2C_TRANS_START_INT_ST_M;
            p_i2c->dev->int_ena.trans_start = 1; // already enabled? why Again?
            p_i2c->dev->int_clr.trans_start = 1; // so that will trigger after next 'END'
        }

        if (activeInt & I2C_TXFIFO_EMPTY_INT_ST) {//should this be before Trans_start?
            fillTxFifo(p_i2c); //fillTxFifo will enable/disable/clear interrupt
            activeInt&=~I2C_TXFIFO_EMPTY_INT_ST;
        }

        if(activeInt & I2C_RXFIFO_FULL_INT_ST) {
            emptyRxFifo(p_i2c);
            p_i2c->dev->int_clr.rx_fifo_full=1;
            p_i2c->dev->int_ena.rx_fifo_full=1; //why?

            activeInt &=~I2C_RXFIFO_FULL_INT_ST;
        }

        if (activeInt & I2C_ACK_ERR_INT_ST_M) {//fatal error, abort i2c service
            if (p_i2c->mode == I2C_MASTER) {
                i2c_update_error_byte_cnt(p_i2c); // calc which byte caused ack Error, check if address or data
                if(p_i2c->errorByteCnt < 0 ) { // address
                    i2cIsrExit(p_i2c,EVENT_ERROR_NAK,true);
                } else {
                    i2cIsrExit(p_i2c,EVENT_ERROR_DATA_NAK,true); //data
                }
            }
            return;
        }

        if (activeInt & I2C_TIME_OUT_INT_ST_M) {
            // let Gross timeout occur, Slave may release SCL before the configured timeout expires
            // the Statemachine only has a 13.1ms max timout, some Devices >500ms
            p_i2c->dev->int_clr.time_out =1;
            activeInt &=~I2C_TIME_OUT_INT_ST;
          // since a timeout occurred, capture the rxFifo data 
            emptyRxFifo(p_i2c);
            p_i2c->dev->int_clr.rx_fifo_full=1;
            p_i2c->dev->int_ena.rx_fifo_full=1; //why?

        }

        if (activeInt & I2C_TRANS_COMPLETE_INT_ST_M) {
            p_i2c->dev->int_clr.trans_complete = 1;
            i2cIsrExit(p_i2c,EVENT_DONE,false);
            return; // no more work to do
            /*
            // how does slave mode act?
            if (p_i2c->mode == I2C_SLAVE) { // STOP detected
            // empty fifo
            // dispatch callback
             */
        }

        if (activeInt & I2C_ARBITRATION_LOST_INT_ST_M) { //fatal
            i2cIsrExit(p_i2c,EVENT_ERROR_ARBITRATION,true);
            return; // no more work to do
        }

        if (activeInt & I2C_SLAVE_TRAN_COMP_INT_ST_M) {
            p_i2c->dev->int_clr.slave_tran_comp = 1;
            // need to complete this !
        }

        if (activeInt & I2C_END_DETECT_INT_ST_M) {
            p_i2c->dev->int_ena.end_detect = 0;
            p_i2c->dev->int_clr.end_detect = 1;
            p_i2c->dev->ctr.trans_start=0;
            fillCmdQueue(p_i2c,true); // enable interrupts
            p_i2c->dev->ctr.trans_start=1; // go for it
            activeInt&=~I2C_END_DETECT_INT_ST_M;
        }

        if(activeInt) { // clear unhandled if possible?  What about Disabling interrupt?
            p_i2c->dev->int_clr.val = activeInt;
            log_e("unknown int=%x",activeInt);
            // disable unhandled IRQ,
            p_i2c->dev->int_ena.val = p_i2c->dev->int_ena.val & (~activeInt);
        }

//        activeInt = p_i2c->dev->int_status.val; // start all over if another interrupt happened
// 01AUG2018 if another interrupt happened, the OS will schedule another interrupt
// this is the source of spurious interrupts
    }
}

/* Stickbreaker added for ISR 11/2017
functional with Silicon date=0x16042000
 */
static i2c_err_t i2cAddQueue(i2c_t * i2c,uint8_t mode, uint16_t i2cDeviceAddr, uint8_t *dataPtr, uint16_t dataLen,bool sendStop, bool dataOnly, EventGroupHandle_t event)
{
    // need to grab a MUTEX for exclusive Queue,
    // what about if ISR is running?

    if(i2c==NULL) {
        return I2C_ERROR_DEV;
    }

    I2C_DATA_QUEUE_t dqx;
    dqx.data = dataPtr;
    dqx.length = dataLen;
    dqx.position = 0;
    dqx.cmdBytesNeeded = dataLen;
    dqx.ctrl.val = 0;
    if( dataOnly) {
     /* special case to add a queue data only element.
        START and devAddr will not be sent, this dq element can have a STOP.
        allows multiple buffers to be used for one transaction.
        sequence: normal transaction(sendStop==false), [dataonly(sendStop==false)],dataOnly(sendStop==true)
       *** Currently only works with WRITE, final byte NAK an READ will cause a fail between dq buffer elements.  (in progress 30JUL2018)
        */
        dqx.ctrl.startCmdSent = 1; // mark as already sent
        dqx.ctrl.addrCmdSent = 1;
    } else {
        dqx.ctrl.addrReq = ((i2cDeviceAddr&0xFC00)==0x7800)?2:1; // 10bit or 7bit address
    }
    dqx.ctrl.addr = i2cDeviceAddr;
    dqx.ctrl.mode = mode;
    dqx.ctrl.stop= sendStop;
    dqx.queueEvent = event;

    if(event) { // an eventGroup exist, so, initialize it
        xEventGroupClearBits(event, EVENT_MASK); // all of them
    }

    if(i2c->dq!=NULL) { // expand
        //log_i("expand");
        I2C_DATA_QUEUE_t* tq =(I2C_DATA_QUEUE_t*)realloc(i2c->dq,sizeof(I2C_DATA_QUEUE_t)*(i2c->queueCount +1));
        if(tq!=NULL) { // ok
            i2c->dq = tq;
            memmove(&i2c->dq[i2c->queueCount++],&dqx,sizeof(I2C_DATA_QUEUE_t));
        } else { // bad stuff, unable to allocate more memory!
            log_e("realloc Failure");
            return I2C_ERROR_MEMORY;
        }
    } else { // first Time
        //log_i("new");
        i2c->queueCount=0;
        i2c->dq =(I2C_DATA_QUEUE_t*)malloc(sizeof(I2C_DATA_QUEUE_t));
        if(i2c->dq!=NULL) {
            memmove(&i2c->dq[i2c->queueCount++],&dqx,sizeof(I2C_DATA_QUEUE_t));
        } else {
            log_e("malloc failure");
            return I2C_ERROR_MEMORY;
        }
    }
    return I2C_ERROR_OK;
}

i2c_err_t i2cAddQueueWrite(i2c_t * i2c, uint16_t i2cDeviceAddr, uint8_t *dataPtr, uint16_t dataLen,bool sendStop,EventGroupHandle_t event)
{
    return i2cAddQueue(i2c,0,i2cDeviceAddr,dataPtr,dataLen,sendStop,false,event);
}

i2c_err_t i2cAddQueueRead(i2c_t * i2c, uint16_t i2cDeviceAddr, uint8_t *dataPtr, uint16_t dataLen,bool sendStop,EventGroupHandle_t event)
{
    //10bit read is kind of weird, first you do a 0byte Write with 10bit
    //  address, then a ReSTART then a 7bit Read using the the upper 7bit +
    // readBit.

    // this might cause an internal register pointer problem with 10bit
    // devices, But, Don't have any to test against.
    // this is the Industry Standard specification.

    if((i2cDeviceAddr &0xFC00)==0x7800) { // ten bit read
        i2c_err_t err = i2cAddQueue(i2c,0,i2cDeviceAddr,NULL,0,false,false,event);
        if(err==I2C_ERROR_OK) {
            return i2cAddQueue(i2c,1,(i2cDeviceAddr>>8),dataPtr,dataLen,sendStop,false,event);
        } else {
            return err;
        }
    }
    return i2cAddQueue(i2c,1,i2cDeviceAddr,dataPtr,dataLen,sendStop,false,event);
}

i2c_err_t i2cProcQueue(i2c_t * i2c, uint32_t *readCount, uint16_t timeOutMillis)
{
    /* do the hard stuff here
    install ISR if necessary
    setup EventGroup
    handle bus busy?
     */
    //log_e("procQueue i2c=%p",&i2c);
    if(readCount){ //total reads accomplished in all queue elements
        *readCount = 0;
    }
    if(i2c == NULL) {
        return I2C_ERROR_DEV;
    }
    if(i2c->debugFlags & 0xff000000) i2cTriggerDumps(i2c,(i2c->debugFlags>>24),"before ProcQueue");
    if (i2c->dev->status_reg.bus_busy) { // return error, let TwoWire() handle resetting the hardware.
        /* if multi master then this if should be changed to this 03/12/2018
        if(multiMaster){// try to let the bus clear by its self
            uint32_t timeOutTick = millis();
            while((i2c->dev->status_reg.bus_busy)&&(millis()-timeOutTick<timeOutMillis())){
              delay(2); // allow task switch
            }
        }
        if(i2c->dev->status_reg.bus_busy){ // still busy, so die
             */
        log_i("Bus busy, reinit");
        return I2C_ERROR_BUSY;
    }

    I2C_MUTEX_LOCK();
    /* what about co-existence with SLAVE mode?
    Should I check if a slaveMode xfer is in progress and hang
    until it completes?
    if i2c->stage == I2C_RUNNING or I2C_SLAVE_ACTIVE
     */
    i2c->stage = I2C_DONE; // until ready

#if (ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO) && (defined ENABLE_I2C_DEBUG_BUFFER)
    for(uint16_t i=0; i<INTBUFFMAX; i++) {
        intBuff[i][0][i2c->num] = 0;
        intBuff[i][1][i2c->num] = 0;
        intBuff[i][2][i2c->num] = 0;
    }
    intPos[i2c->num] = 0;
    fifoPos = 0;
    memset(fifoBuffer,0,FIFOMAX);
#endif
    // EventGroup is used to signal transmission completion from ISR
    // not always reliable. Sometimes, the FreeRTOS scheduler is maxed out and refuses request
    // if that happens, this call hangs until the timeout period expires, then it continues.
    if(!i2c->i2c_event) {
        i2c->i2c_event = xEventGroupCreate();
    }
    if(i2c->i2c_event) {
        xEventGroupClearBits(i2c->i2c_event, 0xFF);
    } else { // failed to create EventGroup
        log_e("eventCreate failed=%p",i2c->i2c_event);
        I2C_MUTEX_UNLOCK();
        return I2C_ERROR_MEMORY;
    }

    i2c_err_t reason = I2C_ERROR_OK;
    i2c->mode = I2C_MASTER;
    i2c->dev->ctr.trans_start=0; // Pause Machine
    i2c->dev->timeout.tout = 0xFFFFF; // max 13ms
    i2c->dev->int_clr.val = 0x1FFF; // kill them All!
    
    i2c->dev->ctr.ms_mode = 1; // master!
    i2c->queuePos=0;
    i2c->errorByteCnt=0;
    i2c->errorQueue = 0;
    uint32_t totalBytes=0; // total number of bytes to be Moved!
    // convert address field to required I2C format
    while(i2c->queuePos < i2c->queueCount) { // need to push these address modes upstream, to AddQueue
        I2C_DATA_QUEUE_t *tdq = &i2c->dq[i2c->queuePos++];
        uint16_t taddr=0;
        if(tdq->ctrl.addrReq ==2) { // 10bit address
            taddr =((tdq->ctrl.addr >> 7) & 0xFE)
                   |tdq->ctrl.mode;
            taddr = (taddr <<8) | (tdq->ctrl.addr&0xFF);
        } else { // 7bit address
            taddr =  ((tdq->ctrl.addr<<1)&0xFE)
                     |tdq->ctrl.mode;
        }
        tdq->ctrl.addr = taddr; // all fixed with R/W bit
        totalBytes += tdq->length + tdq->ctrl.addrReq; // total number of byte to be moved!
    }
    i2c->queuePos=0;

    fillCmdQueue(i2c,false); // don't enable Tx/RX irq's
    // start adding command[], END irq will keep it full
    //Data Fifo will be filled after trans_start is issued
    i2c->exitCode=0;

    I2C_FIFO_CONF_t f;
    f.val = i2c->dev->fifo_conf.val;
    f.rx_fifo_rst = 1; // fifo in reset
    f.tx_fifo_rst = 1; // fifo in reset
    f.nonfifo_en = 0; // use fifo mode
    f.nonfifo_tx_thres = 31;
    // need to adjust threshold based on I2C clock rate, at 100k, 30 usually works,
    // sometimes the emptyRx() actually moves 31 bytes
    // it hasn't overflowed yet, I cannot tell if the new byte is added while
    // emptyRX() is executing or before?
  // let i2cSetFrequency() set thrhds  
  //   f.rx_fifo_full_thrhd = 30; // 30 bytes before INT is issued
  //  f.tx_fifo_empty_thrhd = 0;
    f.fifo_addr_cfg_en = 0; // no directed access
    i2c->dev->fifo_conf.val = f.val; // post them all

    f.rx_fifo_rst = 0; // release fifo
    f.tx_fifo_rst = 0;
    i2c->dev->fifo_conf.val = f.val; // post them all

    i2c->stage = I2C_STARTUP; // everything configured, now start the I2C StateMachine, and
    // As soon as interrupts are enabled, the ISR will start handling them.
    // it should receive a TXFIFO_EMPTY immediately, even before it
    // receives the TRANS_START

    
    uint32_t interruptsEnabled =
        I2C_ACK_ERR_INT_ENA | // (BIT(10))  Causes Fatal Error Exit
        I2C_TRANS_START_INT_ENA | // (BIT(9))  Triggered by trans_start=1, initial,END
        I2C_TIME_OUT_INT_ENA  | //(BIT(8))  Trigger by SLAVE SCL stretching, NOT an ERROR
        I2C_TRANS_COMPLETE_INT_ENA | // (BIT(7))  triggered by STOP, successful exit
        I2C_ARBITRATION_LOST_INT_ENA | // (BIT(5))  cause fatal error exit
        I2C_SLAVE_TRAN_COMP_INT_ENA  | // (BIT(4))  unhandled
        I2C_END_DETECT_INT_ENA  | // (BIT(3))   refills cmd[] list
        I2C_RXFIFO_OVF_INT_ENA  | //(BIT(2))  unhandled
        I2C_TXFIFO_EMPTY_INT_ENA | // (BIT(1))    triggers fillTxFifo()
        I2C_RXFIFO_FULL_INT_ENA;  // (BIT(0))     trigger emptyRxFifo()
  
    i2c->dev->int_ena.val = interruptsEnabled;
 
    if(!i2c->intr_handle) { // create ISR for either peripheral
        // log_i("create ISR %d",i2c->num);
        uint32_t ret = 0;
        uint32_t flags = ESP_INTR_FLAG_IRAM |  //< ISR can be called if cache is disabled
          ESP_INTR_FLAG_LOWMED |   //< Low and medium prio interrupts. These can be handled in C.
          ESP_INTR_FLAG_SHARED; //< Reduce resource requirements, Share interrupts
      
        if(i2c->num) {
            ret = esp_intr_alloc_intrstatus(ETS_I2C_EXT1_INTR_SOURCE, flags, (uint32_t)&i2c->dev->int_status.val, interruptsEnabled, &i2c_isr_handler_default,i2c, &i2c->intr_handle);
        } else {
            ret = esp_intr_alloc_intrstatus(ETS_I2C_EXT0_INTR_SOURCE, flags, (uint32_t)&i2c->dev->int_status.val, interruptsEnabled, &i2c_isr_handler_default,i2c, &i2c->intr_handle);
        }

        if(ret!=ESP_OK) {
            log_e("install interrupt handler Failed=%d",ret);
            I2C_MUTEX_UNLOCK();
            return I2C_ERROR_MEMORY;
        }
        if( !addApbChangeCallback( i2c, i2cApbChangeCallback)) {
            log_e("install apb Callback failed");
            I2C_MUTEX_UNLOCK();
            return I2C_ERROR_DEV;
        }

    }
    //hang until it completes.

    // how many ticks should it take to transfer totalBytes through the I2C hardware,
    // add user supplied timeOutMillis to Calculated Value

    portTickType ticksTimeOut = ((totalBytes*10*1000)/(i2cGetFrequency(i2c))+timeOutMillis)/portTICK_PERIOD_MS;

    i2c->dev->ctr.trans_start=1; // go for it

#if ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_DEBUG
    portTickType tBefore=xTaskGetTickCount();
#endif
    
    // wait for ISR to complete the transfer, or until timeOut in case of bus fault, hardware problem
    
    uint32_t eBits = xEventGroupWaitBits(i2c->i2c_event,EVENT_DONE,pdFALSE,pdTRUE,ticksTimeOut);

#if ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_DEBUG
    portTickType tAfter=xTaskGetTickCount();
#endif


    // if xEventGroupSetBitsFromISR() failed, the ISR could have succeeded but never been
    // able to mark the success

    if(i2c->exitCode!=eBits) { // try to recover from O/S failure
        //  log_e("EventGroup Failed:%p!=%p",eBits,i2c->exitCode);
        eBits=i2c->exitCode;
    }
    if((eBits&EVENT_ERROR)||(!(eBits & EVENT_DONE))){ // need accurate errorByteCnt for debug
      i2c_update_error_byte_cnt(i2c);
    }

    if(!(eBits==EVENT_DONE)&&(eBits&~(EVENT_ERROR_NAK|EVENT_ERROR_DATA_NAK|EVENT_ERROR|EVENT_DONE))) { // not only Done, therefore error, exclude ADDR NAK, DATA_NAK
#if ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_INFO
        i2cDumpI2c(i2c);
        i2cDumpInts(i2c->num);
#endif
    }

    if(eBits&EVENT_DONE) { // no gross timeout
        switch(i2c->error) {
        case I2C_OK :
            reason = I2C_ERROR_OK;
            break;
        case I2C_ERROR :
            reason = I2C_ERROR_DEV;
            break;
        case I2C_ADDR_NAK:
            reason = I2C_ERROR_ACK;
            break;
        case I2C_DATA_NAK:
            reason = I2C_ERROR_ACK;
            break;
        case I2C_ARBITRATION:
            reason = I2C_ERROR_BUS;
            break;
        case I2C_TIMEOUT:
            reason = I2C_ERROR_TIMEOUT;
            break;
        default :
            reason = I2C_ERROR_DEV;
        }
    } else { // GROSS timeout, shutdown ISR , report Timeout
        i2c->stage = I2C_DONE;
        i2c->dev->int_ena.val =0;
        i2c->dev->int_clr.val = 0x1FFF;
        i2c_update_error_byte_cnt(i2c);
        if((i2c->errorByteCnt == 0)&&(i2c->errorQueue==0)) { // Bus Busy no bytes Moved
            reason = I2C_ERROR_BUSY;
            eBits = eBits | EVENT_ERROR_BUS_BUSY|EVENT_ERROR|EVENT_DONE;
#if ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_DEBUG
            log_d(" Busy Timeout start=0x%x, end=0x%x, =%d, max=%d error=%d",tBefore,tAfter,(tAfter-tBefore),ticksTimeOut,i2c->error);
            i2cDumpI2c(i2c);
            i2cDumpInts(i2c->num);
#endif
        } else { // just a timeout, some data made it out or in.
            reason = I2C_ERROR_TIMEOUT;
            eBits = eBits | EVENT_ERROR_TIMEOUT|EVENT_ERROR|EVENT_DONE;

#if ARDUHAL_LOG_LEVEL >= ARDUHAL_LOG_LEVEL_DEBUG
            log_d(" Gross Timeout Dead start=0x%x, end=0x%x, =%d, max=%d error=%d",tBefore,tAfter,(tAfter-tBefore),ticksTimeOut,i2c->error);
            i2cDumpI2c(i2c);
            i2cDumpInts(i2c->num);
#endif
        }
    }

    /* offloading all EventGroups to dispatch, EventGroups in ISR is not always successful
     11/20/2017
       if error, need to trigger all succeeding dataQueue events with the EVENT_ERROR_PREV
     07/22/2018
       Need to use the queueEvent value to identify transaction blocks, if an error occurs,
       all subsequent queue items with the same queueEvent value will receive the EVENT_ERROR_PREV.
       But, ProcQue should re-queue queue items that have a different queueEvent value(different transaction)
       This change will support multi-thread i2c usage.  Use the queueEvent as the transaction event
       identifier.
    */
    uint32_t b = 0;

    while(b < i2c->queueCount) {
        if(i2c->dq[b].ctrl.mode==1 && readCount) {
            *readCount += i2c->dq[b].position; // number of data bytes received
        }
        if(b < i2c->queuePos) { // before any error
            if(i2c->dq[b].queueEvent) { // this data queue element has an EventGroup
                xEventGroupSetBits(i2c->dq[b].queueEvent,EVENT_DONE);
            }
        } else if(b == i2c->queuePos) { // last processed queue
            if(i2c->dq[b].queueEvent) { // this data queue element has an EventGroup
                xEventGroupSetBits(i2c->dq[b].queueEvent,eBits);
            }
        } else { // never processed queues
            if(i2c->dq[b].queueEvent) { // this data queue element has an EventGroup
                xEventGroupSetBits(i2c->dq[b].queueEvent,eBits|EVENT_ERROR_PREV);
            }
        }
        b++;
    }
    if(i2c->debugFlags & 0x00ff0000) i2cTriggerDumps(i2c,(i2c->debugFlags>>16),"after ProcQueue");

    I2C_MUTEX_UNLOCK();
    return reason;
}

static void i2cReleaseISR(i2c_t * i2c)
{
    if(i2c->intr_handle) {
        esp_intr_free(i2c->intr_handle);
        i2c->intr_handle=NULL;
        if (!removeApbChangeCallback( i2c, i2cApbChangeCallback)) {
            log_e("unable to release apbCallback");
        }
    }
}

static bool i2cCheckLineState(int8_t sda, int8_t scl){
     if(sda < 0 || scl < 0){
        return false;//return false since there is nothing to do
    }
    // if the bus is not 'clear' try the cycling SCL until SDA goes High or 9 cycles
    digitalWrite(sda, HIGH);
    digitalWrite(scl, HIGH);
    pinMode(sda, PULLUP|OPEN_DRAIN|INPUT);
    pinMode(scl, PULLUP|OPEN_DRAIN|OUTPUT);

    if(!digitalRead(sda) || !digitalRead(scl)) { // bus in busy state
        log_w("invalid state sda(%d)=%d, scl(%d)=%d", sda, digitalRead(sda), scl, digitalRead(scl));
        digitalWrite(scl, HIGH);
        for(uint8_t a=0; a<9; a++) {
            delayMicroseconds(5);
            digitalWrite(scl, LOW);
            delayMicroseconds(5);
            digitalWrite(scl, HIGH);
            if(digitalRead(sda)){ // bus recovered
                log_d("Recovered after %d Cycles",a+1);
                break;
            }
        }
    }

    if(!digitalRead(sda) || !digitalRead(scl)) { // bus in busy state
        log_e("Bus Invalid State, TwoWire() Can't init sda=%d, scl=%d",digitalRead(sda),digitalRead(scl));
        return false; // bus is busy
    }
    return true;
}

i2c_err_t i2cAttachSCL(i2c_t * i2c, int8_t scl)
{
    if(i2c == NULL) {
        return I2C_ERROR_DEV;
    }
    digitalWrite(scl, HIGH);
    pinMode(scl, OPEN_DRAIN | PULLUP | INPUT | OUTPUT);
    pinMatrixOutAttach(scl, I2C_SCL_IDX(i2c->num), false, false);
    pinMatrixInAttach(scl, I2C_SCL_IDX(i2c->num), false);
    return I2C_ERROR_OK;
}

i2c_err_t i2cDetachSCL(i2c_t * i2c, int8_t scl)
{
    if(i2c == NULL) {
        return I2C_ERROR_DEV;
    }
    pinMatrixOutDetach(scl, false, false);
    pinMatrixInDetach(I2C_SCL_IDX(i2c->num), false, false);
    pinMode(scl, INPUT | PULLUP);
    return I2C_ERROR_OK;
}

i2c_err_t i2cAttachSDA(i2c_t * i2c, int8_t sda)
{
    if(i2c == NULL) {
        return I2C_ERROR_DEV;
    }
    digitalWrite(sda, HIGH);
    pinMode(sda, OPEN_DRAIN | PULLUP | INPUT | OUTPUT );
    pinMatrixOutAttach(sda, I2C_SDA_IDX(i2c->num), false, false);
    pinMatrixInAttach(sda, I2C_SDA_IDX(i2c->num), false);
    return I2C_ERROR_OK;
}

i2c_err_t i2cDetachSDA(i2c_t * i2c, int8_t sda)
{
    if(i2c == NULL) {
        return I2C_ERROR_DEV;
    }
    pinMatrixOutDetach(sda, false, false);
    pinMatrixInDetach(I2C_SDA_IDX(i2c->num), false, false);
    pinMode(sda, INPUT | PULLUP);
    return I2C_ERROR_OK;
}

/*
 * PUBLIC API
 * */
// 24Nov17 only supports Master Mode
i2c_t * i2cInit(uint8_t i2c_num, int8_t sda, int8_t scl, uint32_t frequency) {
#ifdef ENABLE_I2C_DEBUG_BUFFER
  log_v("num=%d sda=%d scl=%d freq=%d",i2c_num, sda, scl, frequency);
#endif
    if(i2c_num > 1) {
        return NULL;
    }

    i2c_t * i2c = &_i2c_bus_array[i2c_num];

    // pins should be detached, else glitch
    if(i2c->sda >= 0){
        i2cDetachSDA(i2c, i2c->sda);
    }
    if(i2c->scl >= 0){
        i2cDetachSCL(i2c, i2c->scl);
    }
    i2c->sda = sda;
    i2c->scl = scl;

#if !CONFIG_DISABLE_HAL_LOCKS
    if(i2c->lock == NULL) {
        i2c->lock = xSemaphoreCreateRecursiveMutex();
        if(i2c->lock == NULL) {
            return NULL;
        }
    }
#endif
    I2C_MUTEX_LOCK();

    i2cReleaseISR(i2c); // ISR exists, release it before disabling hardware

    if(frequency == 0) {// don't change existing frequency
        frequency = i2cGetFrequency(i2c);
        if(frequency == 0) {
            frequency = 100000L;    // default to 100khz
        }
    }

    if(i2c_num == 0) {
        DPORT_SET_PERI_REG_MASK(DPORT_PERIP_RST_EN_REG,DPORT_I2C_EXT0_RST); //reset hardware
        DPORT_SET_PERI_REG_MASK(DPORT_PERIP_CLK_EN_REG,DPORT_I2C_EXT0_CLK_EN);
        DPORT_CLEAR_PERI_REG_MASK(DPORT_PERIP_RST_EN_REG,DPORT_I2C_EXT0_RST);//  release reset
    } else {
        DPORT_SET_PERI_REG_MASK(DPORT_PERIP_RST_EN_REG,DPORT_I2C_EXT1_RST); //reset Hardware
        DPORT_SET_PERI_REG_MASK(DPORT_PERIP_CLK_EN_REG,DPORT_I2C_EXT1_CLK_EN);
        DPORT_CLEAR_PERI_REG_MASK(DPORT_PERIP_RST_EN_REG,DPORT_I2C_EXT1_RST);
    }
    i2c->dev->ctr.val = 0;
    i2c->dev->ctr.ms_mode = 1;
    i2c->dev->ctr.sda_force_out = 1 ;
    i2c->dev->ctr.scl_force_out = 1 ;
    i2c->dev->ctr.clk_en = 1;

    //the max clock number of receiving  a data
    i2c->dev->timeout.tout = 400000;//clocks max=1048575
    //disable apb nonfifo access
    i2c->dev->fifo_conf.nonfifo_en = 0;

    i2c->dev->slave_addr.val = 0;
    I2C_MUTEX_UNLOCK();

    i2cSetFrequency(i2c, frequency);    // reconfigure

    if(!i2cCheckLineState(i2c->sda, i2c->scl)){
        return NULL;
    }

    if(i2c->sda >= 0){
        i2cAttachSDA(i2c, i2c->sda);
    }
    if(i2c->scl >= 0){
        i2cAttachSCL(i2c, i2c->scl);
    }
    return i2c;
}

void i2cRelease(i2c_t *i2c)  // release all resources, power down peripheral
{
    I2C_MUTEX_LOCK();

    if(i2c->sda >= 0){
        i2cDetachSDA(i2c, i2c->sda);
    }
    if(i2c->scl >= 0){
        i2cDetachSCL(i2c, i2c->scl);
    }

    i2cReleaseISR(i2c);

    if(i2c->i2c_event) {
        vEventGroupDelete(i2c->i2c_event);
        i2c->i2c_event = NULL;
    }

    i2cFlush(i2c);

    // reset the I2C hardware and shut off the clock, power it down.
    if(i2c->num == 0) {
        DPORT_SET_PERI_REG_MASK(DPORT_PERIP_RST_EN_REG,DPORT_I2C_EXT0_RST); //reset hardware
        DPORT_CLEAR_PERI_REG_MASK(DPORT_PERIP_CLK_EN_REG,DPORT_I2C_EXT0_CLK_EN); // shutdown hardware
    } else {
        DPORT_SET_PERI_REG_MASK(DPORT_PERIP_RST_EN_REG,DPORT_I2C_EXT1_RST); //reset Hardware
        DPORT_CLEAR_PERI_REG_MASK(DPORT_PERIP_CLK_EN_REG,DPORT_I2C_EXT1_CLK_EN); // shutdown Hardware
    }

    I2C_MUTEX_UNLOCK();
}

i2c_err_t i2cFlush(i2c_t * i2c)
{
    if(i2c==NULL) {
        return I2C_ERROR_DEV;
    }
    i2cTriggerDumps(i2c,i2c->debugFlags & 0xff, "FLUSH");

    // need to grab a MUTEX for exclusive Queue,
    // what out if ISR is running?
    i2c_err_t rc=I2C_ERROR_OK;
    if(i2c->dq!=NULL) {
        //  log_i("free");
        // what about EventHandle?
        free(i2c->dq);
        i2c->dq = NULL;
    }
    i2c->queueCount=0;
    i2c->queuePos=0;
    // release Mutex
    return rc;
}

i2c_err_t i2cWrite(i2c_t * i2c, uint16_t address, uint8_t* buff, uint16_t size, bool sendStop, uint16_t timeOutMillis){
    if((i2c==NULL)||((size>0)&&(buff==NULL))) { // need to have location to store requested data
        return I2C_ERROR_DEV;
    }
    i2c_err_t last_error = i2cAddQueueWrite(i2c, address, buff, size, sendStop, NULL);

    if(last_error == I2C_ERROR_OK) { //queued
        if(sendStop) { //now actually process the queued commands, including READs
            last_error = i2cProcQueue(i2c, NULL, timeOutMillis);
            if(last_error == I2C_ERROR_BUSY) { // try to clear the bus
                if(i2cInit(i2c->num, i2c->sda, i2c->scl, 0)) {
                    last_error = i2cProcQueue(i2c, NULL, timeOutMillis);
                }
            }
            i2cFlush(i2c);
        } else { // stop not received, so wait for I2C stop,
            last_error = I2C_ERROR_CONTINUE;
        }
    }
    return last_error;
}

i2c_err_t i2cRead(i2c_t * i2c, uint16_t address, uint8_t* buff, uint16_t size, bool sendStop, uint16_t timeOutMillis, uint32_t *readCount){
    if((size == 0)||(i2c == NULL)||(buff==NULL)){ // hardware will hang if no data requested on READ
        return I2C_ERROR_DEV;
    }
    i2c_err_t last_error=i2cAddQueueRead(i2c, address, buff, size, sendStop, NULL);

    if(last_error == I2C_ERROR_OK) { //queued
        if(sendStop) { //now actually process the queued commands, including READs
            last_error = i2cProcQueue(i2c, readCount, timeOutMillis);
            if(last_error == I2C_ERROR_BUSY) { // try to clear the bus
                if(i2cInit(i2c->num, i2c->sda, i2c->scl, 0)) {
                    last_error = i2cProcQueue(i2c, readCount, timeOutMillis);
                }
            }
            i2cFlush(i2c);
        } else { // stop not received, so wait for I2C stop,
            last_error = I2C_ERROR_CONTINUE;
        }
    }
    return last_error;
}

#define MIN_I2C_CLKS 100              // minimum ratio between cpu and i2c Bus clocks
#define INTERRUPT_CYCLE_OVERHEAD 16000 // number of cpu clocks necessary to respond to interrupt
i2c_err_t i2cSetFrequency(i2c_t * i2c, uint32_t clk_speed)
{
    if(i2c == NULL) {
        return I2C_ERROR_DEV;
    }
    uint32_t apb = getApbFrequency(); 
    uint32_t period = (apb/clk_speed) / 2;

    if((apb/8192 > clk_speed)||(apb/MIN_I2C_CLKS < clk_speed)){ //out of bounds
        log_d("i2c freq(%d) out of bounds.vs APB Clock(%d), min=%d, max=%d",clk_speed,apb,(apb/8192),(apb/MIN_I2C_CLKS));
    }
    if(period < (MIN_I2C_CLKS/2) ){
        period = (MIN_I2C_CLKS/2);
        clk_speed = apb/(period*2);
        log_d("APB Freq too slow, Reducing i2c Freq to %d Hz",clk_speed);
    } else if ( period> 4095) {
        period = 4095;
        clk_speed = apb/(period*2);
        log_d("APB Freq too fast, Increasing i2c Freq to %d Hz",clk_speed);
    }
#ifdef ENABLE_I2C_DEBUG_BUFFER
    log_v("freq=%dHz",clk_speed);
#endif      
    uint32_t halfPeriod = period/2;
    uint32_t quarterPeriod = period/4;

    I2C_MUTEX_LOCK();

    I2C_FIFO_CONF_t f;

    f.val    = i2c->dev->fifo_conf.val;
/*  Adjust Fifo thresholds based on differential between cpu frequency and bus clock.
    The fifo_delta is calculated such that at least INTERRUPT_CYCLE_OVERHEAD cpu clocks are
    available when a Fifo interrupt is triggered.  This allows enough room in the Fifo so that
    interrupt latency does not cause a Fifo overflow/underflow event.
*/
#ifdef ENABLE_I2C_DEBUG_BUFFER
    log_v("cpu Freq=%dMhz, i2c Freq=%dHz",getCpuFrequencyMhz(),clk_speed);
#endif
    uint32_t fifo_delta = (INTERRUPT_CYCLE_OVERHEAD/((getCpuFrequencyMhz()*1000000 / clk_speed)*10))+1; 
    if (fifo_delta > 24) fifo_delta=24;   
    f.rx_fifo_full_thrhd = 32 - fifo_delta;
    f.tx_fifo_empty_thrhd = fifo_delta;
    i2c->dev->fifo_conf.val = f.val; // set thresholds
#ifdef ENABLE_I2C_DEBUG_BUFFER
    log_v("Fifo delta=%d",fifo_delta);
#endif
    //the clock num during SCL is low level
    i2c->dev->scl_low_period.period = period;
    //the clock num during SCL is high level
    i2c->dev->scl_high_period.period = period;

    //the clock num between the negedge of SDA and negedge of SCL for start mark
    i2c->dev->scl_start_hold.time = halfPeriod;
    //the clock num between the posedge of SCL and the negedge of SDA for restart mark
    i2c->dev->scl_rstart_setup.time = halfPeriod;

    //the clock num after the STOP bit's posedge
    i2c->dev->scl_stop_hold.time = halfPeriod;
    //the clock num between the posedge of SCL and the posedge of SDA
    i2c->dev->scl_stop_setup.time = halfPeriod;

    //the clock num I2C used to hold the data after the negedge of SCL.
    i2c->dev->sda_hold.time = quarterPeriod;
    //the clock num I2C used to sample data on SDA after the posedge of SCL
    i2c->dev->sda_sample.time = quarterPeriod;
    I2C_MUTEX_UNLOCK();
    return I2C_ERROR_OK;
}

uint32_t i2cGetFrequency(i2c_t * i2c)
{
    if(i2c == NULL) {
        return 0;
    }
    uint32_t result = 0;
    uint32_t old_count = (i2c->dev->scl_low_period.period+i2c->dev->scl_high_period.period);
    if(old_count>0) {
        result = getApbFrequency() / old_count;
    } else {
        result = 0;
    }
    return result;
}


uint32_t i2cDebug(i2c_t * i2c, uint32_t setBits, uint32_t resetBits){
    if(i2c != NULL) {
        i2c->debugFlags = ((i2c->debugFlags | setBits) & ~resetBits);
        return i2c->debugFlags;
    }
    return 0;
    
 }
 
uint32_t i2cGetStatus(i2c_t * i2c){
    if(i2c != NULL){
        return i2c->dev->status_reg.val;
    }
    else return 0;
}


/* todo
  22JUL18
    need to add multi-thread capability, use dq.queueEvent as the group marker. When multiple threads
    transactions are present in the same queue, and an error occurs, abort all succeeding unserviced transactions
    with the same dq.queueEvent value.  Succeeding unserviced transactions with different dq.queueEvent values
    can be re-queued and processed independently. 
  30JUL18 complete data only queue elements, this will allow transfers to use multiple data blocks, 
 */