After watching the schematic of the Arduino Serial Single Sided, I wonder:
Couldn't be replaced the 2 transistors close to the serial conector by a MAX232 or ST232 DIP IC ?
I think the 232 device would give volt signals more accurate to what the serial protocol expects.
Placing a 232 would increase the size of the board, but as the Serial Single Sided is thought for handmaking, I think a little size increase would not be a problem.
Any opinion will be welcome.