From what I know that would be quite a phone & phone/service to have a 115200 bps air-wave bandwidth!!

The phone probably is able to autobuad to a range of host serial baud rates at first establishment of the COMM connection. If you trial checked the phone with a PC connection, via a terminal program, you may have incorrectly concluded that the phone always worked at 115200 bps. If this is the case I would encourage you to re-trial it at say 9600 baud or 19200.

Keep in mind that unless you are just sending very short messages back and forth in a burst mode manner it would be advisable to use a serial port baud rate that was faster than the net throughput of the phone network's airwave channel. This way you can avoid some buffer underrun and overrun issues when the microcontroller assumes the commumications duties with the mobile phone.

If your phone is indeed a delux model on a special contract network service with true 115200 bps network support then you are going to have to look for a microcontroller capable of operating its UART at this speed. I have been successful with 115200 bps serial communications when using the SiLabs C8051F12x series parts at @ 22.1184 MHz.

Michael Karas