Hi all. I recently built the single sided serial arduino. I do not want to use the arduino software to program with it however. Basically I just want to use the board as is and program it with my AVRISP mkII. If I do this, can I use the serial port for a debug terminal? The thing is, I don't really understand how the TX and RX parts of the circuit work. It seems that one of the pins on the DB9 connector is connected directly to the reset because of how the arduino bootloader works.
My question is, do I have to make any modifications to the circuit to use it the way I want to?
As you wish to use it, the capacitor connected between the serial DTR signal and the AVR reset pin should be removed, unless you have a specific application where you want to be able to reset the board via the comm link.
Of course you also have no need for the bootloader, but that should be gone the first time you erase and write a new program, although I think you will have to do some fuse changes to be able to erase it I think, not sure about that.
Other then that it's just a generic micro-controller board, with a serial link. The hardware serial port capablities is fully described in the AVR data sheet. It is presently hardwired to the RS-232 level changer chip for communication with any standard RS-232 communication channel. If you needed to use those two I/O pins for other then serial communications, then simply removing the serial convert chip should make those two hardwired traces just dead end spurs.
The single sided serial I built a a year or two ago doesn't have autoreset capability. Does yours actually have the autoreset? If so, all you have to do is remove the capacitor (typically 0.1uF) that's between the handshake line and the reset line.
The schematic for the single sided board is shown here: http://arduino.cc/en/uploads/Main/ArduinoSeverinoSchematic.png. There is no serial converter chip in this schematic. I am assuming that all the stuff on the bottom left does the level converting. There is an autoreset jumper here, however. This means I don't have to do anything to the circuit as long as I don't jump those 2 pins correct?
