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Maximum UART Baud?


I’ve managed to write a fairly complete library to interface with the µVGA-II. One issue I seem to be having is communicating with the device at any speed above 115200 baud.

I’ve managed to do the baud-switch from the initial 9600 baud to start communication, but if I select either of the two possible higher modes 128000 or 256000, communication fails. Looking at the responses back from the device, I occasionally get a NAK (bad input, message not recieved) among a mess of fairly random extra data which makes it look like some sort of synchronization issue. I’m fairly sure I’m not near hitting the peak of serial com speed. I also understand that it could be more of an issue with the module, vs. the dev hardware, but I figured I’d ask you guys.

Have any ideas?


After you open the port, use register class to write directly to the processor to set your high baud very accurately then use a scope to verify.


Thanks for the quick reply!

I actually just figured it out about 2 minutes ago, and it’s the strangest thing. I did a quick Google search for “256K baud” (out of desperation/curiosity) to see if there was any strange definition of what 256K actually meant, like 256### baud. The first result brought me to the 4D Systems forum ( where someone else was having the same issue with a similar product. Somehow, setting the module to “256K” and the Fez to “281000” seems to fix the issue.

On the off chance anyone else uses the module, this info might come in handy.


Or better share the code on code-share? :slight_smile: