> >> Now I have another really confusing problem. Anything I write to SPI is > >> written little endian. The tcan chip expects big endian. > >> Anything I read from SPI is treated as little endian but is big endian. > >> Does anyone know why this happens? > >> Is there a flag or something I can set for the SPI device/wire to fix this? > > > > Have you changed the bits_per_word to 8? Then you read just a stream > > of bytes. If you tread them as an u32 they are in host order. > >
@Marc Yes, I changed bits_per_word to 8. Since the PI does not support any values apart from 8 and 9 this seems to be the only way. > > Marc > > > > > Hi, > > from my experience with SPIDEV on RPI, the driver uses a char array for I/O. > As the RPI code is build little endian, logically little endian comes out of > SPI. You > basically have to invert the bit and byte order by hand for a big endian > slave. > @Patrick, Marc You both are right. This seems to be the problem. The SPI driver uses char arrays and the tcan driver treats them as u32. I will try to change the byte order by hand to get it running for my project. But in the long run, this does not seem to be a proper solution... Regards, Konstantin > Clock Phase and Clock Polarity are also an issue on the RPI as at least SPIDEV > kindly overlooks any options set previously. > I had my share of this while writing a test app for a MAX31855 IC and ended up > casting a little endian array to a big endian structure. > > Regards, > Patrick
