I2C and Multithreading problem Topic is solved

[JanS]

Hi,

I'm using a STM32F030 board to communicate with a LSM303D sensor board via I2C using the ChibiOS I2CDriver. I want to read data periodically from the sensor. Everything works fine as long as I use the main thread for the I2C communication. Now I tried to create a second thread to read the data. But this second thread gets stuck on the i2cMasterTransmit method.

Here is the code that I used:

Code: Select all

#include <hal.h>
#include <ch.hpp>

using namespace chibios_rt;

#define DEVICE_ADR 0x1D
#define CTRL1_SETTINGS 0x07

static THD_WORKING_AREA(waThd1, 128);

static I2CConfig i2cdConfig = {
      STM32_TIMINGR_PRESC(0xBU)  |      // fI2CCLK = 48MHz
      STM32_TIMINGR_SCLDEL(0x4U) | STM32_TIMINGR_SDADEL(0x2U) |
      STM32_TIMINGR_SCLH(0xC3U)  | STM32_TIMINGR_SCLL(0xC7U),
      0,
      0
};

void configureAccelerometer(uint16_t freq) {
   uint8_t writeBuffer[2];
   writeBuffer[0] = 0x20;
   writeBuffer[1] = (freq << 4) | CTRL1_SETTINGS;
   i2cMasterTransmit(&I2CD1, DEVICE_ADR, writeBuffer, 2, NULL, 0);
}

static THD_FUNCTION(thd1, arg) {
   (void) arg;
   while(true) {
      uint8_t subAddr = 0x0F;   // WHO_AM_I register
      uint8_t receiveBuffer;
      i2cMasterTransmit(&I2CD1, DEVICE_ADR, &subAddr, 1 , &receiveBuffer, 1);
      chThdSleepMilliseconds(1000);
   }
}

int main() {
   halInit();
   System::init();

   i2cStart(&I2CD1, &i2cdConfig);
   configureAccelerometer(10);   // 10 = frequency 1600 Hz

   chThdCreateStatic(waThd1, sizeof(waThd1), NORMALPRIO + 1, thd1, NULL);

   while(true) {}
}

With the code I try to read the WHO_AM_I register.
If I move the while loop to the main thread the read is successful and the correct value (0x49) is returned. I also made sure that the THD_FUNCTION is executed (I was able to blink an LED with it). Just the I2C communication won't work.

I'm quite new to multithreading in ChibiOS, so forgive me if I made a rookie mistake

Thanks in advance for your help

Jan

[Marco]

Hi,

You should yield from the main loop, for example with chThdSleepMilliseconds(1000). Otherwise the main loop starves the other thread.

Marco

[JanS]

Hi,

thanks for the quick reply. I tried adding chThdSleepMilliseconds(1000) to the main loop. Unfortunatly the problem remains.

Jan

[Giovanni]

Do you have the usual debug options enabled in chconf.h?

See this article: http://www.chibios.org/dokuwiki/doku.ph ... ebug_guide

Giovanni

[JanS]

Hi,

yes, and I just found out that ch.dbg.panic_msg reports a stack overflow. But I cannot figure out what causes this.

Jan

[Giovanni]

Well, you should look at the generated code or just increase the stack size in the working area.

Giovanni

[JanS]

Hi,

I really thought 128 byte would be enough for I2C communication. But apparantly this was the problem all along. I increased the working area to 256 byte and it works. Thanks for the help

Jan

[Giovanni]

Hi,

The debug plugin in ChibiStudio allows to know exactly how much stack space is used by threads, you may want to give it a try.

Giovanni

[JanS]

Hi,

thanks for the recommendation, I wll try it out.

Jan