Re: 20 bit UART for 5912OSK

*** top-posting fixed ***

Andrew M wrote: 
<sillycar@xxxxxxxxx> wrote in message

Greetings, I am having some problems with the UART protocol. To my limited knowledge, I know that the UART is capable of handling more than the usual 8 data bits. I would need the OMAP to receive 20 bits of data from an external device. My guess is the UART is the most suitable protocol to handle this. However, being 20 data bits, how can I configure the UART code to handle this? I know I need to insert a start and stop bit to make it into a frame but I am not well versed in ANSI C. Any suggestions? Any kind of help would be appreciated. Thanks for looking.

If you need to ask this question you shouldn't be playing with products as complex as OMAP.

The UART bit patterns are 7,8 or 9 bits maximum. To transmit longer objects you'll need to encapsulate them into a frame of
multiple bytes. 

Please don't top-post.  I fixed this one.

The reason for the UART bit length limitation is that both ends have to agree on the actual baud rate. The result must sample the final stop bit correctly. For 10 total bits (8 data, plus start and stop) this means the frequencies must agree within at least 5%, assuming exact accuracy in locating the start bit. Things only get worse from there. For 20 or so bits that number is about 2%, and the initial sampling accuracy will probably not let it work at all.

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