Joseph
I fully expect that after you reset the processor and send the "U" character that if you see the echo then the auto baud algorithm is complete. I have been on the implementing end of such an algorithm and found that the detection only took one transmission of the U character. If the host sees the echo correctly then you know that the microcontroller has locked onto the baud rate properly.

I would like to add the following comment. I have seen some auto-baud algorithms that measure the edges of the character coming in and will then set the baud rate as close as possible to the incoming bit rate. In other words they set the baud rate in an almost continuously variable manner in order to lock in on ANY baud rate (all within the resolution of the measuring clock of the target microcontroller of course). This type of scheme is, in my opinion, not the best scheme and should only be used if the target microcontroller running the autobaod algorithm does not know what its clocking frequency is. In cases where the clocking rate of the target microcontroller is known, then the better way is to measure the incoming character timing and then find the closest baud rate in a look up table that specifies a range of standard baud rates such as 1200, 2400, 9600, 14400, etc. This way when the microcontroller finds the baud rate then the corresponding delivered baud rate supplied by the microcontroller can be exact standard baud rates instead of some intermediate measured baud rate that is off due to sampling error, signal distortion, or noise.

Michael Karas