Phase 2: RS-232 blues

Waylaid by my need to get the terminal and monitor program tested. First the serial port. Found two errors ... after hours on the scope


1. I had mistakenly tied one end of one of the charge pump capacitors to ground. That would be capacitor C81 between pin 2 of the MAX232 level converter and ground instead of VCC

2. Digging through the MAX232 datasheet, I realized the charge pump capacitors I chose were 0.1uF. These are recommended when VCC is 3.3v. When its 5v (as in my design) the charge pump capacitors must not be less than 1uF.

So I had them replaced along with the ttl-to-rs232 level converter.

Went back and checked and double checked the UART baud rate clock and fractional divider parameters for both 9600 baud and 115200 baud. The peripheral clock is 40Mhz ... derived from the base 120Mhz system clock.