FAQ: I heard there is some issue with hardware SPI? And full-duplex SPI?

[Lazar Demin]

The Omega2 does not support full-duplex SPI transmissions. This is due to a hardware bug in the underlying MT7688 SoC used in the Omega2.

On the bright side, half-duplex SPI transmissions will work. We've done some work to improve the speed and stability of half-duplex transmissions, read more about it here.

When working with SPI on the Omega, we recommend:

• Using the python-spidev module
• Writing C code that directly uses the Linux spidev interface
  • General information can be found here: https://www.kernel.org/doc/Documentation/spi/spidev
  • And here is a good example of how it can be used: http://linux-sunxi.org/SPIdev#In_the_user_space

A few additional notes:

• The spi-tool utility and the pyOnionSpi module are deprecated and should not be used

[Lazar Demin]

Half Duplex SPI Transactions

If you're looking to do a half-duplex SPI transaction (where Chip-Select is held active between blocks), check out the xfer3 function in the python-spidev module.

Details:

• In the python-spidev module readme
• An example of usage in a community thread

If you absolutely need full-duplex SPI

The Omega2 family does not support full-duplex transactions on the hardware SPI bus, but you can make a software (bit-bang) instance of an SPI bus that will support full-duplex.

More info on software-based SPI buses in this FAQ post.