Hi, gents,
I have some need to use SPI slave mode instead of working SPI master mode.
I'm tranferring 22 16-bit words from Infineon slave board at 6Mhz clock rate, once per 100 ns, and have 4-line interface including CS line. Due to noisy lines I prefer to reset communication before each 22x16 bit transfer.
The picture is attached - the 4th line represents CS signal, the 2nd line - data sent from STM32, line 3 is zero as zeros are sent.
After some attempts to write the code I came to solution, when I'm attaching a low-priority EXTI interrupt to SPI5 NSS pin (PF6 GPIO pin), and this interrupt has the following code (this code worked OK for master mode):
if (GPIO_Pin == GPIO_PIN_6)
{
if (hspi5.State != HAL_SPI_STATE_READY)
{ HAL_SPI_DMAStop(&hspi5); }
HAL_StatusTypeDef td = HAL_SPI_TransmitReceive_DMA(&hspi5,(uint8_t*)spi2CAT, (uint8_t*)CAT2spi, CAT_PACK_SIZE*(sizeof(int32_t)/2));
tdd = td;
SPI_cnt++;
}
The code works as in picture, except one point: it inserts 1 extra 16-bit word during transmission.
If I remove HAL_SPI_DMAStop() - synchorization may be lost and data are corrupted.
Maybe I need to insert some wait cycle, but I'm inside an interrupt, which can be interrupted by higher priority interrupt. Placing HAL_SPI_TransmitReceive_DMA() into receive completion callback also looses sync.
Question: for this code, may something is not cleared in SPI transmit/receive buffer? Maybe I've overlooked simpler method?
