Hello. I am struggling to understand how to properly use SPI interface.
As far as I understand, every SPI communication starts with an instruction byte which specifies whether we want to READ or WRITE and then followed by a register address. After that, the DATA that we want to write or read.
SPI slave device:
https://www.mouser.co.uk/datasheet/2/949/w25m02gv_revf_050918_unsecured-1489896.pdf
Something like that :
I have generated my STM32 project using STM32cubeMX and the generated SPI libraries dont make any sense to me at all.
This is the generated code for the SPI transmit, however, I dont seem to understand how do I address the instruction byte and the register address?
Have anyone used stm32cubemx generated SPI library and could give me some guidance?
As far as I understand, every SPI communication starts with an instruction byte which specifies whether we want to READ or WRITE and then followed by a register address. After that, the DATA that we want to write or read.
SPI slave device:
https://www.mouser.co.uk/datasheet/2/949/w25m02gv_revf_050918_unsecured-1489896.pdf
Something like that :
I have generated my STM32 project using STM32cubeMX and the generated SPI libraries dont make any sense to me at all.
C:
HAL_StatusTypeDef HAL_SPI_Transmit(SPI_HandleTypeDef *hspi, uint8_t *pData, uint16_t Size, uint32_t Timeout)
{
uint32_t tickstart;
HAL_StatusTypeDef errorcode = HAL_OK;
uint16_t initial_TxXferCount;
/* Check Direction parameter */
assert_param(IS_SPI_DIRECTION_2LINES_OR_1LINE(hspi->Init.Direction));
/* Process Locked */
__HAL_LOCK(hspi);
/* Init tickstart for timeout management*/
tickstart = HAL_GetTick();
initial_TxXferCount = Size;
if (hspi->State != HAL_SPI_STATE_READY)
{
errorcode = HAL_BUSY;
goto error;
}
if ((pData == NULL) || (Size == 0U))
{
errorcode = HAL_ERROR;
goto error;
}
/* Set the transaction information */
hspi->State = HAL_SPI_STATE_BUSY_TX;
hspi->ErrorCode = HAL_SPI_ERROR_NONE;
hspi->pTxBuffPtr = (uint8_t *)pData;
hspi->TxXferSize = Size;
hspi->TxXferCount = Size;
/*Init field not used in handle to zero */
hspi->pRxBuffPtr = (uint8_t *)NULL;
hspi->RxXferSize = 0U;
hspi->RxXferCount = 0U;
hspi->TxISR = NULL;
hspi->RxISR = NULL;
/* Configure communication direction : 1Line */
if (hspi->Init.Direction == SPI_DIRECTION_1LINE)
{
SPI_1LINE_TX(hspi);
}
#if (USE_SPI_CRC != 0U)
/* Reset CRC Calculation */
if (hspi->Init.CRCCalculation == SPI_CRCCALCULATION_ENABLE)
{
SPI_RESET_CRC(hspi);
}
#endif /* USE_SPI_CRC */
/* Check if the SPI is already enabled */
if ((hspi->Instance->CR1 & SPI_CR1_SPE) != SPI_CR1_SPE)
{
/* Enable SPI peripheral */
__HAL_SPI_ENABLE(hspi);
}
/* Transmit data in 16 Bit mode */
if (hspi->Init.DataSize == SPI_DATASIZE_16BIT)
{
if ((hspi->Init.Mode == SPI_MODE_SLAVE) || (initial_TxXferCount == 0x01U))
{
hspi->Instance->DR = *((uint16_t *)hspi->pTxBuffPtr);
hspi->pTxBuffPtr += sizeof(uint16_t);
hspi->TxXferCount--;
}
/* Transmit data in 16 Bit mode */
while (hspi->TxXferCount > 0U)
{
/* Wait until TXE flag is set to send data */
if (__HAL_SPI_GET_FLAG(hspi, SPI_FLAG_TXE))
{
hspi->Instance->DR = *((uint16_t *)hspi->pTxBuffPtr);
hspi->pTxBuffPtr += sizeof(uint16_t);
hspi->TxXferCount--;
}
else
{
/* Timeout management */
if ((((HAL_GetTick() - tickstart) >= Timeout) && (Timeout != HAL_MAX_DELAY)) || (Timeout == 0U))
{
errorcode = HAL_TIMEOUT;
goto error;
}
}
}
}
/* Transmit data in 8 Bit mode */
else
{
if ((hspi->Init.Mode == SPI_MODE_SLAVE) || (initial_TxXferCount == 0x01U))
{
*((__IO uint8_t *)&hspi->Instance->DR) = (*hspi->pTxBuffPtr);
hspi->pTxBuffPtr += sizeof(uint8_t);
hspi->TxXferCount--;
}
while (hspi->TxXferCount > 0U)
{
/* Wait until TXE flag is set to send data */
if (__HAL_SPI_GET_FLAG(hspi, SPI_FLAG_TXE))
{
*((__IO uint8_t *)&hspi->Instance->DR) = (*hspi->pTxBuffPtr);
hspi->pTxBuffPtr += sizeof(uint8_t);
hspi->TxXferCount--;
}
else
{
/* Timeout management */
if ((((HAL_GetTick() - tickstart) >= Timeout) && (Timeout != HAL_MAX_DELAY)) || (Timeout == 0U))
{
errorcode = HAL_TIMEOUT;
goto error;
}
}
}
}
This is the generated code for the SPI transmit, however, I dont seem to understand how do I address the instruction byte and the register address?
Have anyone used stm32cubemx generated SPI library and could give me some guidance?
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