# Do you know how to use USART on STM32?

I've been doing USART on STM32 and got this at putty:

Actually I want to display :

printf("*  Thank you for using the board");


Do you have idea why ?

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Did you set identical configurations (data bits, parity, stop bits, bauds) at both ends? – Telaclavo Apr 17 '12 at 12:21
Fix already, I forgot to put MX232 converter, thanks a lot .. – Rick Ant Apr 18 '12 at 13:14
If you fixed it by adding a MAX232 converter put that as your answer and accept it. – mjh2007 Apr 18 '12 at 17:32

This could be a whole host of things. The best thing to do in trouble shooting is to avoid or clarify assumptions:

• Correct baud rate?(too high?) Check both sides
• Incorrect COM port settings (start/stop/data/parity bits). Check both sides. Don't assume values, like writing 1 in the stop bit register means 1 stop bit. At NXP LPC2129 (ARM7) this means 2 stop bits. Once I was stuck on that for hours, figuring out why I couldn't send more than 1 character at a time..
• Check timing on scope or logic analyser (at 9600baud a short pulse should take 1/9600 second). If you're using high baud rates and a 'odd crystal' (20MHz on 115k2 or higher), you may need to set up a fractional baud rate divider to more closely match baud rates.
• Rerun calculations from datasheet for baud rate. Look-up, measure, clarify all clock speeds and other dividers configurable.

Edit: last but not least: is your hardware OK? Shorts, missing solder points, components, etc.

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 Fix already, I forgot to put MX232 converter, thanks a lot . – Rick Ant Apr 18 '12 at 13:14

I agree...

decypher attempt.. a lot more characters suggests Putty speed is too fast. a lot of 5's . 5 ascii = 53d=35h= 00110101 now read from right to left LSB 1st.. hmmm ó ascii = 162d=A2h=10100010 failed... read UART basics http://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitter then fix match settings.

A really neat trick I used to do in the 70's was make a duplex or Y cable for serial port and record data or scope it while connected to device. Autobaud receivers units were really nice back then until I had to design one.

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You are probably at the wrong baud rate in putty.

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Fix already, I forgot to put MX232 converter.

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