ChibiOS Free Embedded RTOS

Posted: **Fri Apr 17, 2020 7:16 pm**

Hi,

I am using an STM32F042 and I want to use the I2C and SPI drivers together. Due to the DMA stream overlap, I need to use the start/stop functionality in both drivers. Still, there seems to be some conflict and I get broken data reception and transmission on SPI. I cannot exactly tell what is wrong (no scope at the moment) but I receive wrong data, and my peripherals behave incorrectly.

If I disable my I2C thread, including all data exchange, the problems reduce to SPI reception errors. When I remove the spiStop() command, everything is fine. Is something wrong with spiStop()?

Here is my spiHelper that exchanges data with the peripherals. It is inspired by the demo applications. I am also using a semaphore that prevents I2C and SPI from acting at the same time.

Thanks in advance!

Code: Select all

void spiExchangeHelper(SPIDriver *spi, const SPIConfig *conf, uint32_t length, uint8_t *txbuf, uint8_t *rxbuf)
{
    chBSemWait(&dma_lock);

    spiStart(spi, conf);
    /* Bus acquisition and SPI reprogramming.*/
    spiAcquireBus(spi);

    /* Slave selection and data transmission.*/
    spiSelect(spi);

    if (rxbuf != NULL && txbuf != NULL) // exchange data
        spiExchange(spi, length, txbuf, rxbuf);

    else if (txbuf != NULL && rxbuf == NULL) // only send
        spiSend(spi, length, txbuf);

    else if (rxbuf != NULL && txbuf == NULL) // only receive
        spiReceive(spi, length, rxbuf);

    spiUnselect(spi);

    /* Releasing the bus.*/
    spiReleaseBus(spi);
    //spiStop(spi);

    chBSemSignal(&dma_lock);
}

Posted: **Fri Apr 17, 2020 8:24 pm**

Try enabling assertions, do you get some error?

Giovanni

Posted: **Fri Apr 17, 2020 8:51 pm**

No, I do have them enabled already.

Currently, I have two slaves on the SPI bus: A display and a temperature sensor, with a chip select each. The data that I receive from the temperature sensor is byte-swapped (it is 16 bit long), when I use the spiStop() command.

Posted: **Fri Apr 17, 2020 8:59 pm**

Try putting a small delay before spiStop and/or i2cStop then see if it changes anything, it could be an hint about the problem.

Giovanni

Posted: **Fri Apr 17, 2020 9:23 pm**

Ok, I tried a delay of up to 100ms (chThdSleepMilliseconds), but the bytes are still flipped. Should the delay be blocking or is sleep sufficient? I will compare the dma registers of the two implementations tomorrow, if there is some issue to be found in those.

Posted: **Sat Apr 18, 2020 7:06 am**

You should check if the DMA channels are disabled when xxxStop() is executed. I have no other ideas about the "swap" problem, probably we are not looking at the right thing.

Giovanni

ChibiOS Free Embedded RTOS

spiStop() breaks SPI reception on STM32F042

spiStop() breaks SPI reception on STM32F042

Re: spiStop() breaks SPI reception on STM32F042

Re: spiStop() breaks SPI reception on STM32F042

Re: spiStop() breaks SPI reception on STM32F042

Re: spiStop() breaks SPI reception on STM32F042

Re: spiStop() breaks SPI reception on STM32F042