Problems reading SSI encoder devices using SPI Master RX only on STM32F405RGTx I got an angle encoder with SSI interface, which is Synchronized Serial Interface. The output data is 21-bit. No CS signal is needed.I have implemented using SPI1 master mode RX only reading this encoder, with SPI_CLK as the serial clock and SPI_MISO for data input. The data size to read is set to 3 bytes, but the clock is transmitted one more byte as intended. HOW DID THIS HAPPEN? Does the SPI send a dummy address on receiving?The clock is generated immediately upon calling __attribute__((aligned(4))) uint8_t raw_angle[16] = {0};
HAL_SPI_Receive_IT(&hspi1, raw_angle, 3);The data captured by logic analyzer:The CubeMX setting is as below: I found that SPI_SR_RXNE is left triggered after 3 bytes read by the HAL API, so I have to clear the flag before calling HAL_SPI_Receive_IT. while((SPI1->SR & SPI_SR_RXNE)){
SPI1->DR;
}
HAL_SPI_Receive_IT(&hspi1, raw_angle, 3); I have also tried DMA mode using HAL_SPI_Receive_DMA(&hspi1,
