Question
STM32H7 SPI MOSI Signal changing before the CLK and observed the pulse
STM32H7 SPI configured as Master with the Clock Phase and Clock Polarity 0 (mode 0). During the HAL_SPI_TransmitReceive() call, before the CLK the pulse is observed on the MOSI signal. Due to this the slave device is behaving differently. Agree the slave device should consider the data w.r.t clock, but for some use cases, our slave doesn't expect any change in the MOSI signal.
We would like to know the workaround for this (i.e MOSI should toggle/change the state only w.r.t the clock).
Please find the picture shown for reference.
Following is the initialization part.
/**
* @brief SPI6 Initialization Function
* @param None
* @retval None
*/
static void MX_SPI6_Init(void)
{
/* USER CODE BEGIN SPI6_Init 0 */
/* USER CODE END SPI6_Init 0 */
/* USER CODE BEGIN SPI6_Init 1 */
/* USER CODE END SPI6_Init 1 */
/* SPI6 parameter configuration*/
hspi6.Instance = SPI6;
hspi6.Init.Mode = SPI_MODE_MASTER;
hspi6.Init.Direction = SPI_DIRECTION_2LINES;
hspi6.Init.DataSize = SPI_DATASIZE_8BIT;
hspi6.Init.CLKPolarity = SPI_POLARITY_LOW;
hspi6.Init.CLKPhase = SPI_PHASE_1EDGE;
hspi6.Init.NSS = SPI_NSS_SOFT;
hspi6.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_8;
hspi6.Init.FirstBit = SPI_FIRSTBIT_MSB;
hspi6.Init.TIMode = SPI_TIMODE_DISABLE;
hspi6.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
hspi6.Init.CRCPolynomial = 0x0;
hspi6.Init.NSSPMode = SPI_NSS_PULSE_ENABLE;
hspi6.Init.NSSPolarity = SPI_NSS_POLARITY_LOW;
hspi6.Init.FifoThreshold = SPI_FIFO_THRESHOLD_01DATA;
hspi6.Init.TxCRCInitializationPattern = SPI_CRC_INITIALIZATION_ALL_ZERO_PATTERN;
hspi6.Init.RxCRCInitializationPattern = SPI_CRC_INITIALIZATION_ALL_ZERO_PATTERN;
hspi6.Init.MasterSSIdleness = SPI_MASTER_SS_IDLENESS_00CYCLE;
hspi6.Init.MasterInterDataIdleness = SPI_MASTER_INTERDATA_IDLENESS_00CYCLE;
hspi6.Init.MasterReceiverAutoSusp = SPI_MASTER_RX_AUTOSUSP_DISABLE;
hspi6.Init.MasterKeepIOState = SPI_MASTER_KEEP_IO_STATE_DISABLE;
hspi6.Init.IOSwap = SPI_IO_SWAP_DISABLE;
if (HAL_SPI_Init(&hspi6) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN SPI6_Init 2 */
/* USER CODE END SPI6_Init 2 */
}