Hi, you can't really tell if you have signals by using a voltmeter. The voltmeter will intergrate the signals. As the uART sends the signal it shifts the contents of the xmtr buffer one bit. But in your code, you constantly re-write it, overwritting what was shifted.But you are not writing over it in sync to the UART. Its possible that every so often a one gets through. This effect would be different at different baud rates. Its also possible that you "confuse" the logic in the UART by writing when it isn't ready. I would try changing your code to my suggestions. Let me know how that works out. Until you fix the code we can't tell if there really is anything wrong with your MAX232 wiring.