Is it possible to implement UART by GPIO?

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From: P (nospamp_at_hotmail.com)
Date: 01/12/05 

Date: 12 Jan 2005 00:34:32 -0800

I'm sure sending is possible on a PXA255, if the transfer speed is not
too high. But not using the OS Sleep and Timer functions, which only
use millisecond intervals. You would have to use the OSCR register in
the PXA255 and implement busy waiting in a high priority thread.
Receiving would be even harder because you would have to tell the
difference between 1 and 2 bit times to keep track of the number of
bits.

I wouldn't do it, your timings will not be very good, you will bot be
able to do anything else while transferring data and most of all it's
just not something you want to do in software.

I did't know there was a thing like 9 bit data in serial
communications? Are you sure it's not 8 + parity? Which reminds me,
you could send 9 bit data by manipulating the parity setting every
time before sending a byte, depending on what you want as last bit.
Now that would be fun! Receiving seems a bit harder though, you would
have to be fast enough to check the parity error after every single
byte (and PXA255 would have to let you read the bytes with a parity
error, I'm not really sure about that).

Another idea: do you have control over this 8051 you're communicating
with? Can you not switch this to 8 bit or change your protocol so the
ninth bit is ignored?

Good luck with it,

P

BTW Sorry I started a new thread, anyone know why I get "Unable to
retrieve message OzpoAi$9EHA.3820@TK2MSFTNGP11.phx.gbl" when trying to
reply to a message?

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