topic freertos spi : wait transfer to finish problem in Kinetis Software Development Kit

freertos spi : wait transfer to finish problem

mr_max — Mon, 18 Jul 2016 01:27:21 GMT

Hi,

I am facing problems with fsl_spi_freertos API lib. When I use SPI_RTOS_Transfer() method (see detail below) with a output data length less then 4 bytes, SPI_RTOS_Transfer() stuck forever at :

/* Wait for transfer to finish */ xSemaphoreTake(handle->event, portMAX_DELAY);

portMAX_DELAY set timeout to an infinity duration. And if I change portMAX_DELAY to 100ms for example, error happen at next call of SPI_RTOS_Transfer() with an error type kStatus_SPI_Busy. So no transfer occurred at the second call.

To resume :

//Call with timeout = portMAX_DELAY SPI_RTOS_Transfer() //Wait transfer to finish for ever  ...  //First call with timeout = 100ms. SPI_RTOS_Transfer() //Ok, no problem  //Second call and so on SPI_RTOS_Transfer() //method return error  kStatus_SPI_Busy

Now, if a I do the same thing with 4 bytes output, SPI_RTOS_Transfer() don't block at all in any case...

And this is pretty annoying because my application does a lot of quick SPI transfer with less then 4 bytes.

So why and how can I solve this ?

I am working with FRDM-KL46Z, KSDKv2, KDSv3

Here is the FreeRTOS SPI method (from fsl_spi_freertos.c)

status_t SPI_RTOS_Transfer(spi_rtos_handle_t *handle, spi_transfer_t *transfer) {     status_t status;      /* Lock resource mutex */     if (xSemaphoreTake(handle->mutex, portMAX_DELAY) != pdTRUE)     {         return kStatus_SPI_Busy;     }      status = SPI_MasterTransferNonBlocking(handle->base, &handle->drv_handle, transfer);     if (status != kStatus_Success)     {         xSemaphoreGive(handle->mutex);         return status;     }      /* Wait for transfer to finish */     xSemaphoreTake(handle->event, portMAX_DELAY);      /* Unlock resource mutex */     xSemaphoreGive(handle->mutex);      /* Return status captured by callback function */     return handle->async_status; }

Re: freertos spi : wait transfer to finish problem

danielchen — Wed, 27 Jul 2016 04:16:52 GMT

Hi Maxime:

Have you enabled tx FIFO mode?

Regards

Daniel

Re: freertos spi : wait transfer to finish problem

mr_max — Wed, 27 Jul 2016 20:01:20 GMT

Hi Daniel,

I initialise SPI with API function SPI_MasterGetDefaultConfig() :

void SPI_MasterGetDefaultConfig(spi_master_config_t *config)
{
    config->enableMaster = true;
    config->enableStopInWaitMode = false;
    config->polarity = kSPI_ClockPolarityActiveHigh;
    config->phase = kSPI_ClockPhaseFirstEdge;
    config->direction = kSPI_MsbFirst;
#if defined(FSL_FEATURE_SPI_16BIT_TRANSFERS) && FSL_FEATURE_SPI_16BIT_TRANSFERS
    config->dataMode = kSPI_8BitMode;
#endif /* FSL_FEATURE_SPI_16BIT_TRANSFERS */
#if defined(FSL_FEATURE_SPI_HAS_FIFO) && FSL_FEATURE_SPI_HAS_FIFO
    config->txWatermark = kSPI_TxFifoOneHalfEmpty;
    config->rxWatermark = kSPI_RxFifoOneHalfFull;
#endif /* FSL_FEATURE_SPI_HAS_FIFO */
    config->pinMode = kSPI_PinModeNormal;
    config->outputMode = kSPI_SlaveSelectAutomaticOutput;
    config->baudRate_Bps = 500000U;
}

Lines betwen FSL_FEATURE_SPI_HAS_FIFO are not greyed, so I guess that tx FIFO is enabled but not sure (?)

I checked my SPI port and I can see correct bytes outputs.

Still have no idea what is wrong.

Re: freertos spi : wait transfer to finish problem

Jmart — Fri, 29 Jul 2016 13:29:42 GMT

Maxime,

I've asked the development team to take a look at your use case to determine the root cause of your issue. You should see a response once they are able to look into the issue.

Thanks,

Jason

Re: freertos spi : wait transfer to finish problem

mr_max — Sat, 30 Jul 2016 00:48:09 GMT

Ok thank you.

I am using the blocking SPI_MasterTransferBlocking() method. It work but I really prefer to use the non blocking SPI_RTOS_Transfer() method in order to have a better integrity with FreeRTOS philosophy.

Waiting for your update.

Re: freertos spi : wait transfer to finish problem

mr_max — Sun, 14 Aug 2016 20:46:22 GMT

Hi Jason,

Did you have some news to my issue ?

Re: freertos spi : wait transfer to finish problem

danielchen — Sun, 18 Sep 2016 08:55:35 GMT

Hi Maxime:

There is a watermark feature when FIFO is enabled. When the data < water mark, the SPI module is requesting more entries to be added to the TxFIFO. From your description, it seems the water mark is 32 bits.

I think you can try to disable the FIFO feature if you need to transfer data less than 4 bytes

Regards

Daniel