linux: CH341 + RF95: GPIO questions and issue

[rpinewbie]

Hello,

I built a DIY module with CH341 (USB->SPI) + RF95.
I am connecting the USB device to linux x86 host running Ubuntu 22.04.

I am struggling to get the device detected by meshtasticd, mainly identify which pins must be in the config.

I use spi-ch341-usb kernel module driver which I configured that way:

struct ch341_pin_config ch341_board_config[CH341_GPIO_NUM_PINS] =
{
    // pin  GPIO mode           GPIO name   hwirq
    {   15, CH341_PIN_MODE_CS , "cs0"     , 0 }, 
    {   16, CH341_PIN_MODE_IN , "busy"     , 0 }, 
    {   17, CH341_PIN_MODE_OUT , "reset"     , 0 }, 
    {   19, CH341_PIN_MODE_IN , "int"   , 0 }, /
};

Once the module is loaded and the USB device plugged, here is the linux system status:

 cat /sys/kernel/debug/gpio
gpiochip0: GPIOs 512-515, parent: usb/2-1, ch341, can sleep:
 gpio-512 (busy                |busy                ) in  lo
 gpio-513 (reset               |reset               ) out lo
 gpio-514 (int                 |int                 ) in  hi

gpioinfo
gpiochip0 - 4 lines:
       line   0:       "busy"       "busy"   input  active-high [used]
       line   1:      "reset"      "reset"  output  active-high [used]
       line   2:        "int"        "int"   input  active-high [used]

My first questions are about the pin numbering I should use in the config:

1. should it be the 0-2 range? or the 512-514 range?
2. the SPI CS0 does not appear as GPIO pin, so which number should I use in the config?

(I will provide meshtastic config files and log output later on, based on those first questions)
(yes I already tried many different configurations with only failing results going from "cannot attach pin" to segfault errors.)

Thanks in advance for your support.

[rpinewbie]

I experimented further using another CH341 driver:
https://github.com/frank-zago/ch341-i2c-spi-gpio

With that driver, the CS0 GPIO pin is visible despite being "used" by SPI device.

 gpioinfo
gpiochip0 - 16 lines:
        line   0:      unnamed        "CS0"  output  active-high [used]
        line   1:      unnamed       unused   input  active-high
        line   2:      unnamed       unused   input  active-high
        line   3:      unnamed        "SCK"  output  active-high [used]
        line   4:      unnamed       unused   input  active-high
        line   5:      unnamed       "MOSI"  output  active-high [used]
        line   6:      unnamed       unused   input  active-high
        line   7:      unnamed       "MISO"   input  active-high [used]
        line   8:      unnamed       unused   input  active-high
        line   9:      unnamed       unused   input  active-high
        line  10:      unnamed       unused   input  active-high
        line  11:      unnamed       unused   input  active-high
        line  12:      unnamed       unused   input  active-high
        line  13:      unnamed       unused   input  active-high
        line  14:      unnamed       unused   input  active-high
        line  15:      unnamed       unused   input  active-high

cat /sys/kernel/debug/gpio
gpiochip0: GPIOs 512-527, parent: platform/ch341-gpio.1.auto, ch341-gpio.1.auto, can sleep:
 gpio-512 (                    |CS0                 ) out hi
 gpio-515 (                    |SCK                 ) out lo
 gpio-517 (                    |MOSI                ) out hi
 gpio-519 (                    |MISO                ) in  hi

I then use the the following Meshtasticd config:

 cat /etc/meshtasticd/config.d/lora-ch341-RF95.yaml
Lora:
  Module: RF95
  CS: 0
  IRQ: 10
  Reset: 2
  Busy: 1
  gpiochip: 0

SPI:
  spidev: /dev/spidev0.0

  USB_PID: 0x5512
  USB_VID: 0x1A86

Which results in the following log output when starting Meshtasticd:

Aug 12 20:34:51 meshtastic-1 systemd[1]: meshtasticd.service: Scheduled restart job, restart counter is at 4.
Aug 12 20:34:51 meshtastic-1 systemd[1]: Started meshtasticd.service - Meshtastic Native Daemon.
Aug 12 20:34:51 meshtastic-1 meshtasticd[6929]: Portduino is starting, VFS root at /var/lib/meshtasticd/.portduino/default
Aug 12 20:34:51 meshtastic-1 meshtasticd[6929]: Set up Meshtastic on Portduino...
Aug 12 20:34:51 meshtastic-1 meshtasticd[6929]: Using /etc/meshtasticd/config.yaml as config file
Aug 12 20:34:51 meshtastic-1 meshtasticd[6929]: Also using "/etc/meshtasticd/config.d/lora-ch341-RF95.yaml" as additional config file
Aug 12 20:34:51 meshtastic-1 meshtasticd[6929]: MAC ADDRESS: BC:24:11:AB:6C:F1
Aug 12 20:34:51 meshtastic-1 meshtasticd[6929]: Warning, cannot claim pin GPIO0St16invalid_argument
Aug 12 20:34:51 meshtastic-1 meshtasticd[6929]: Error setting pin number 0. It may not exist, or may already be in use.
Aug 12 20:34:51 meshtastic-1 systemd[1]: meshtasticd.service: Main process exited, code=exited, status=1/FAILURE
Aug 12 20:34:51 meshtastic-1 systemd[1]: meshtasticd.service: Failed with result 'exit-code'.

So the question about "which GPIO pin to use for CS" is still an open one....

Any idea?