I am investigating ways to interface a AM335x with a 9-bit serial protocol. I am aware that the AM335x does not support support 9-bit data through the UART hardware. Our board will be Linux as an OS.
The protocol I wish to implement is an Multi-Drop Bus protocol. The AM335x master side needs to be able to set the 9th bit on the first byte of every transmission (This is the address byte). All of the following bytes do not have the bit set. When receiving bytes only the last byte will have the 9-bit set. The AM335x will only be used on the master side of this protocol.
I'm thinking there are a few ways of doing this:
1) Emulate the 9-bit serial using the mark and space parity settings.
Something similar to this: http://www.lothosoft.ch/thomas/libmip/markspaceparity.php
2) Use a modified version of the Software UART firmware in the PRU that is provided by TI. This seems like it would work but I am unsure of the amount of work involved. Plus it has the overhead of learning to write assembler for the PRU.
3) Use a small micro that is capable of 9-bit serial as a converter. I understand what this entails and it seems less like a hack then the other two methods. However I would like to avoid having to add hardware components to the project if possible.
Anyone have any experience or thoughts on trying to accomplish this?
