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STM32F051 USART Not working

Question asked by prinster.jim on Feb 1, 2013
Latest reply on Feb 5, 2013 by prinster.jim
I created some simple code on the STM32F05-Discovery board to write a byte of data repeatedly out USART1.  However when I run this code on my target board the USART doesn't send the data.  The TXE line goes low and never comes up so the USART is effectively dead.  (USART2 seems to be working fine, but I need that for another purpose so I can't just switch.)  Has anyone seen this problem? 

The Discovery board runs an STM32F051R8 (64 pin) while my target board runs an STM32F051C8 (48 pin).  On both boards USART1-TX is PA.9, so I shouldn't have any pin reassignments.  My code enables no other I/O pins or any other functions of the chip other than USART1.  My target processor is running since I can step through the code with a debugger.

I'm stumped, and ST hasn't responded to my questions other than asking for code.  The errata sheets don't mention any issues with the USART. 

I tried replacing the chip on my target just in case it was damaged, but that didn't make any difference.  My next step is to try the C6 or C4 version in case there is a die error.

Has anyone seen this problem or have any suggestions?

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