Posted on April 08, 2014 at 16:53Maybe some of you with SPI experience can spot this one easily. I have a SPI slave device connected to my STM8L152. I watch the clock and data stream to the device requesting a read of a register, and then I can see the proper bit stream returned on the MISO line. However, I cannot get the STM8L's RX buffer to read the thing correctly. In fact, it rarely changes no matter what the bit pattern I see on the line. I have tried both phase polarities, and I am confident the clock polarity should be ''idle low''. Here is the short section of code, using only standard library calls, following the protocol as I understand it to be from the User's Manual (pg 549, ''full duplex''). I break on a line following the last and read the returned result. Any suggestions are welcome. Thanks.
//send byte through the SPI peripheral
SPI_SendData(SPI1, 0x42);
//loop while DR register in not empty
while (SPI_GetFlagStatus(SPI1, SPI_FLAG_TXE) == RESET);
//send redundant byte through the SPI peripheral (clocks in response to first read)
SPI_SendData(SPI1, 0x42);
//wait to receive a byte
while (SPI_GetFlagStatus(SPI1, SPI_FLAG_RXNE) == RESET);
// Return the byte read from the SPI bus
spiByte = SPI_ReceiveData(SPI1);
#spi
