On my pocket beagle, which runs Debian, I have three spidev devices (spidev1.0, spidev2.0 and spidev2.1).
I have a SPI temp sensor on spi1 (which is spidev2.0 and spidev2.1). Loopback tests on 2.0 (by jumpering MOSI and MISO) worked. The data came back to me. However I was unable to send data to the temp sensor. When I switched to 2.1, everything worked normally.
Why is that? What is the difference between 2.0 and 2.1?