Function AFERead16BitBuffer() function in afe_config.c does not return a status

Question

I am running the Analog Devices EVAL-ADE9430 board and noticed if I enable CRC checking reading 32 bit registers fail while 16-bit registers always pass.

I trace it down to the AFERead16BitBuffer() function not returning a status after reading the register over the SPI bus. This allows 16 bit register reads to work all the time while 32 Bit registers fail all the time (that's another story).

See line 12 below: HAL_SPI_Receive(&hSPI, (uint8_t *)&pData[0], 2 * numSamples, SPI_TIMEOUT);

uint32_t AFERead16BitBuffer(uint16_t addr, uint16_t numSamples, uint16_t *pData)
{
 int32_t status = SYS_STATUS_SUCCESS;

 cmdBuffer[0] = (addr >> 4);
 cmdBuffer[1] = ((addr & 0x0F) << 4) + 8;

 HAL_GPIO_WritePin(GPIOD, GPIO_PIN_14, GPIO_PIN_RESET);
 status = HAL_SPI_Transmit(&hSPI, (uint8_t *)&cmdBuffer, 2, SPI_TIMEOUT);
 if (status == 0)
 {
 HAL_SPI_Receive(&hSPI, (uint8_t *)&pData[0], 2 * numSamples, 
 SPI_TIMEOUT);
 }
 HAL_GPIO_WritePin(GPIOD, GPIO_PIN_14, GPIO_PIN_SET);

 SwapEndian16Bit(&pData[0], numSamples);

 DEBUG_MSG("REG16RD,0x%x,0x%x", addr, pData[0]);

 return status;
}

Compare this to the uint32_t AFERead32BitBuffer(), line 17 below which returns a status.

uint32_t AFERead32BitBuffer(uint16_t addr, uint16_t numSamples, uint32_t *pData)
{
 int32_t status = SYS_STATUS_SUCCESS;

 cmdBuffer[0] = (addr >> 4);
 cmdBuffer[1] = ((addr & 0x0F) << 4) + 8;

 HAL_GPIO_WritePin(GPIOD, GPIO_PIN_14, GPIO_PIN_RESET);
 status = HAL_SPI_Transmit(&hSPI, (uint8_t *)&cmdBuffer, 2, SPI_TIMEOUT);
 /* FIXME : Handling SPI_Transmit error*/
 if (status != 0)
 {
 status = HAL_SPI_Transmit(&hSPI, (uint8_t *)&cmdBuffer, 2, SPI_TIMEOUT);
 }
 if (status == 0)
 {
 status = HAL_SPI_Receive(&hSPI, (uint8_t *)&pData[0], 4 * numSamples,
 SPI_TIMEOUT);
 }
 HAL_GPIO_WritePin(GPIOD, GPIO_PIN_14, GPIO_PIN_SET);
 SwapEndian32Bit(&pData[0], numSamples);

 DEBUG_MSG("REG32RD,0x%x,0x%x", addr, pData[0]);

 return status;
}

Thanks - mike

Amy323 · Accepted Answer

In AFERead16BitBuffer(), it looks like the receive result is getting ignored. You set status from HAL_SPI_Transmit(), but HAL_SPI_Receive() runs without assigning its return value back to status.

So this line:

HAL_SPI_Receive(&hSPI, (uint8_t *)&pData[0], 2 * numSamples, SPI_TIMEOUT);

could probably be:

status = HAL_SPI_Receive(&hSPI, (uint8_t *)&pData[0], 2 * numSamples, SPI_TIMEOUT);

That would make the function report a receive failure properly, same as the 32-bit version. Also worth being careful with the endian swap and debug print after a failed receive, since the buffer may not contain valid data in that case.

Pavel’s point about CRC is worth checking too, but the missing status assignment in the 16-bit path does look like a real bug either way.

Pavel A. · Answer

Are you sure that the CRC algo of the STM32 SPI matches the CRC algo of the AD device? Would it be better to do the CRC in software?

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