SPI CRC via DMA dosen't work

[UlfS]

Dear ST,

I use STM32F777 and try to receive SPI Data as a slave via SPI DMA. That works only pretty fine, when I don't activate the CRC Checksum calculation. I receive after the DMA threshold the expected data, but when I set: 

.CRCCalculation = SPI_CRCCALCULATION_ENABLE, 

The received data traped in a Error Callback from the SPI, always.

All my init values of the SPI are vaild, look like here:

.SPI_CONFIG = {.Mode = SPI_MODE_SLAVE,

                                                             .Direction = SPI_DIRECTION_2LINES_RXONLY,

                                                             .DataSize = SPI_DATASIZE_8BIT,

                                                             .CLKPolarity = SPI_POLARITY_LOW, // => CPOL = 1

                                                             .CLKPhase = SPI_PHASE_2EDGE, //=> CPHA = 0

                                                             .NSS =  SPI_NSS_SOFT, //SPI_NSS_HARD_INPUT,

                                                             .BaudRatePrescaler = SPI_BAUDRATEPRESCALER_2,

                                                             .FirstBit = SPI_FIRSTBIT_MSB,

                                                             .TIMode = SPI_TIMODE_DISABLE,

                                                             .CRCCalculation = SPI_CRCCALCULATION_ENABLE, // ToDo activate CRC

                                                             .CRCPolynomial = CRC16_CCIT_ZERO, // ToDo activate CRC

                                                             .CRCLength =   SPI_CRC_LENGTH_16BIT,//, //ToDo activate CRC

                                                             .NSSPMode = SPI_NSS_PULSE_DISABLE},

Poly is 0x1021

Inti value is 0x0000

If I use the CRC HW Unit via SW, that works as well. But I still have to use the combination of DMA and CRC, because that part is on our application, very time critical. I still can not use the CPU instead.

[waclawek.jan]

Disclaimer: I've never used the CRC facility in STM32 SPI.

> The received data traped in a Error Callback from the SPI, always.

What is "Error Callback from the SPI"?

Do you use some "library"? Which one? How? Why? Did you try your own code with possibly better control?

Have you tried using polled implementation?

> Dear ST,

While this forum is monitored by ST, it's primarily user-driven.

JW

[UlfS]

Hi JW,

ErrorCallBack is: 

HAL_SPI_ErrorCallback()

Do you use some "library"? Which one?

STM32F7xx_HAL_Driver

Files include:

stm32f7xx_hal_crc.c

stm32f7xx_hal_spi.c

> Did you try your own code with possibly better control?

Yes and no, we use from ecomatic a layer on top, to deal with all possible transmission-ways like: Transmit Only / Receive Only, TransmitReceive and Error.  But this works!

The part which dosent work is located deeper in the HAL lib from ST. Because the Error happens after I trigger the DMA request, to wait till x Bytes are received. After receiving, a ITR will called which works without CRC Enable. 

The SPI Master is an FPGA which send these Data till the end with a 16bit CRC checksum.

When I read the Register SPI DR from CRC HW unit, the 16bit value is completly different as I expected from the crc of the FPGA. 

Again, When I use instead the internal HW CRC in SW, initialize it, the CRC calculation is correct?!

But I can use the HW Unit in SW, unfortunate I dont have this time, these must be calculate during the DMA is receiving datas.

>Have you tried using polled implementation?

No, is not really a solution for me. When the DMA + CRC calculation is finish, a ITR should be raised (Callback).

Did you have a idea?

Thanks again

Ulf

[waclawek.jan]

So, the problem is, that CRC calculated by the SPI unit does not match CRC calculated by FPGA, correct?

Can you give a couple of examples?

JW

[UlfS]

Example: Teststring= 0xA5 A6 8C 00

Poly= 0x1021

Init Value=0x0000

I would be expect as result= 0x07 FA

I try to verify the CRC from DR register at least and got: 0x008C

When is use the the SW calculation routine I got also the result 0x7FA

[UlfS]

I have the feeling CRC->DR is only 8bit wide? I wondering why is the value only 0x8c, looks like a copy of the third byte.

I configure:

     .DataSize = SPI_DATASIZE_8BIT, 

     .CRCLength =   SPI_CRC_LENGTH_16BIT,

8bit input data and 16bit output crc

[waclawek.jan]

I'm confused: are you talking about the CRC module or about the CRC feature of SPI module?

In the latter case, you'd be presumably looking at the content of SPIx_RXCRCR.

Using DMA may be tricky: the CRC feature in SPI apparently assumes, that master actually transmits the CRC after data.

JW

[UlfS]

Jan the Master send the CRC 16bit in the data end. I need to use the CRC on the SPI with DMA. 

x 8 bit data Input

16 bit crc output. See example above.

This fails all the time in a SPI Error, because the SPI Errocode shows me 0x2

[UlfS]

Any updates regarding that problem? The problem is still not solved and need attention from STM.

[Choz]

Hello Ulfs,
CRC peripheral is only CRC32 with polynomial 0x4C11DB7. The configuration below you provided is related to CRC calculator of SPI peripheral.

.CRCCalculation = SPI_CRCCALCULATION_ENABLE, // ToDo activate CRC
.CRCPolynomial = CRC16_CCIT_ZERO, // ToDo activate CRC

So CRC->DR register has nothing to do with your implementation. I suggest you to review the section "CRC transfer managed by DMA" under SPI in reference manual.

For any CRC calculation this site helps a lot: https://www.sunshine2k.de/coding/javascript/crc/crc_js.html.

As waclawek.jan suggested, check content of SPIx_RXCRCR as well.