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UART not sending out messages unless I single step with the debugger

Question asked by Wood.Robert on Apr 14, 2016
Latest reply on Apr 14, 2016 by Clive One

I've been on this problem from over a day and am just utterly bewildered by it. I'm just hoping someone might be able to suggest something that might help me track this down.

I have set up a DMA to send information out of a UART. If I set a break point and step through the code to this line:

DMA_Cmd(DMA_Channel4, ENABLE);

And then step over that with the debugger, the scope shows the 16 bytes I requested sent out exactly correctly.

If I just free run the program nothing goes out. Even if I have the debugger two lines above and hit F5 to resume it won't send.

If anyone can think of anything at all to try I would be most grateful. I've never come across anything like this.