Changes UART ISR to only trigger on RX FIFO Full and timeout

Author: SuGlider

cores/esp32/HardwareSerial.cpp

@@ -140,7 +140,7 @@ _txBufferSize(0),
 _onReceiveCB(NULL), 
 _onReceiveErrorCB(NULL),
 _onReceiveTimeout(true),
-_rxTimeout(10),
+_rxTimeout(1),
 _eventTask(NULL)
 #if !CONFIG_DISABLE_HAL_LOCKS
     ,_lock(NULL)
@@ -212,6 +212,18 @@ void HardwareSerial::onReceive(OnReceiveCb function, bool onlyOnTimeout)
     HSERIAL_MUTEX_UNLOCK();
 }
 
+// This function allow the user to define how many bytes will trigger an Interrupt that will copy RX FIFO to the internal RX Ringbuffer
+// ISR will also move data from FIFO to RX Ringbuffer after a RX Timeout defined in HardwareSerial::setRxTimeout(uint8_t symbols_timeout)
+// A low value of FIFO Full bytes will consume more CPU time within the ISR
+// A high value of FIFO Full bytes will make the application wait longer to have byte available for the Stkech in a streaming scenario
+// Both RX FIFO Full and RX Timeout may affect when onReceive() will be called
+void HardwareSerial::setRxFIFOFull(uint8_t fifoBytes)
+{
+    HSERIAL_MUTEX_LOCK();
+    uartSetRxFIFOFull(_uart, fifoBytes); // Set new timeout
+    HSERIAL_MUTEX_UNLOCK();
+}
+
 // timout is calculates in time to receive UART symbols at the UART baudrate.
 // the estimation is about 11 bits per symbol (SERIAL_8N1)
 void HardwareSerial::setRxTimeout(uint8_t symbols_timeout)
@@ -223,7 +235,7 @@ void HardwareSerial::setRxTimeout(uint8_t symbols_timeout)
     _rxTimeout = symbols_timeout;   
     if (!symbols_timeout) _onReceiveTimeout = false;  // only when RX timeout is disabled, we also must disable this flag 
 
-    if(_uart != NULL) uart_set_rx_timeout(_uart_nr, _rxTimeout); // Set new timeout
+    uartSetRxTimeout(_uart, _rxTimeout); // Set new timeout
 
     HSERIAL_MUTEX_UNLOCK();
 }
@@ -367,7 +379,7 @@ void HardwareSerial::begin(unsigned long baud, uint32_t config, int8_t rxPin, in
 
     // Set UART RX timeout
     if (_uart != NULL) {
-        uart_set_rx_timeout(_uart_nr, _rxTimeout);
+        uartSetRxTimeout(_uart, _rxTimeout);
     }
 
     HSERIAL_MUTEX_UNLOCK();

cores/esp32/HardwareSerial.h

@@ -81,6 +81,12 @@ class HardwareSerial: public Stream
     //                       For a baudrate of 9600, SERIAL_8N1 (10 bit symbol) and symbols_timeout = 3, the timeout would be 3 / (9600 / 10) = 3.125 ms
     void setRxTimeout(uint8_t symbols_timeout);
 
+    // setRxFIFOFull(uint8_t fifoBytes) will set the number of bytes that will trigger UART_INTR_RXFIFO_FULL interrupt and fill up RxRingBuffer
+    // This affects some functions such as Serial::available() and Serial.read() because, in a UART flow of receiving data, Serial internal 
+    // RxRingBuffer will be filled only after these number of bytes arrive or a RX Timeout happens.
+    // This parameter can be set to 1 in order to receive byte by byte, but it will also consume more CPU time as the ISR will be activates often.
+    void setRxFIFOFull(uint8_t fifoBytes);
+
     // onReceive will setup a callback that will be called whenever an UART interruption occurs (UART_INTR_RXFIFO_FULL or UART_INTR_RXFIFO_TOUT)
     // UART_INTR_RXFIFO_FULL interrupt triggers at UART_FULL_THRESH_DEFAULT bytes received (defined as 120 bytes by default in IDF)
     // UART_INTR_RXFIFO_TOUT interrupt triggers at UART_TOUT_THRESH_DEFAULT symbols passed without any reception (defined as 10 symbos by default in IDF)

cores/esp32/esp32-hal-uart.c

@@ -162,6 +162,12 @@ uart_t* uartBegin(uint8_t uart_nr, uint32_t baudrate, uint32_t config, int8_t rx
     uart_config.rx_flow_ctrl_thresh = rxfifo_full_thrhd;
     uart_config.source_clk = UART_SCLK_APB;
 
+    uart_intr_config_t uart_intr = {
+        .intr_enable_mask = UART_INTR_RXFIFO_FULL | UART_INTR_RXFIFO_TOUT,   // only these IRQs - no BREAK, PARITY or OVERFLOW
+        .rx_timeout_thresh = 1,
+        .txfifo_empty_intr_thresh = 10,
+        .rxfifo_full_thresh = rxfifo_full_thrhd,
+    };
 
     ESP_ERROR_CHECK(uart_driver_install(uart_nr, rx_buffer_size, tx_buffer_size, 20, &(uart->uart_event_queue), 0));
     ESP_ERROR_CHECK(uart_param_config(uart_nr, &uart_config));
@@ -173,12 +179,37 @@ uart_t* uartBegin(uint8_t uart_nr, uint32_t baudrate, uint32_t config, int8_t rx
         ESP_ERROR_CHECK(uart_set_line_inverse(uart_nr, UART_SIGNAL_TXD_INV | UART_SIGNAL_RXD_INV));    
     }
 
+    // override default RX IDF Driver Interrupt - no BREAK, PARITY or OVERFLOW
+    ESP_ERROR_CHECK(uart_intr_config(uart_nr, &uart_intr));
+    
     UART_MUTEX_UNLOCK();
 
     uartFlush(uart);
     return uart;
 }
 
+void uartSetRxTimeout(uart_t* uart, uint8_t numSymbTimeout)
+{
+    if(uart == NULL) {
+        return;
+    }
+
+    UART_MUTEX_LOCK();
+    uart_set_rx_timeout(uart->num, numSymbTimeout);
+    UART_MUTEX_UNLOCK();
+}
+
+void uartSetRxFIFOFull(uart_t* uart, uint8_t numBytesFIFOFull)
+{
+    if(uart == NULL) {
+        return;
+    }
+
+    UART_MUTEX_LOCK();
+    uart_set_rx_full_threshold(uart->num, numBytesFIFOFull);
+    UART_MUTEX_UNLOCK();
+}
+
 void uartEnd(uart_t* uart)
 {
     if(uart == NULL) {

cores/esp32/esp32-hal-uart.h

@@ -82,6 +82,8 @@ void uartSetBaudRate(uart_t* uart, uint32_t baud_rate);
 uint32_t uartGetBaudRate(uart_t* uart);
 
 void uartSetRxInvert(uart_t* uart, bool invert);
+void uartSetRxTimeout(uart_t* uart, uint8_t numSymbTimeout);
+void uartSetRxFIFOFull(uart_t* uart, uint8_t numBytesFIFOFull);
 
 void uartSetDebug(uart_t* uart);
 int uartGetDebug();