I have an Arduino Duemilanove board as well as an Oceanserver OS5000S digital compass. I have blunt cut wires for the compass that provide for an RS232 connection, and am connecting the Arduino board via USB. Does this mean I can't use digital ports 0 and 1 for the compass? Anybody have any suggestions on which ports to use or if I can even use this board? Thanks
ahuwaa
If you are using USB for programming, you cannot use the serial port (0&1) while programming, because both signals come in the same hardware pins.
You can not use serial comm. on pin 0 and 1 if you have USB hooked up to a PC at the same time.
If the USB is only used for programming the Arduino and then disconnected you are ok, if you remove your compass from pin 1 and 0 during the programming.
Otherwise you can use the newsoftserial library to create additional (software based) serial communication on any digital pins you want.
Soft serial have some limitations as compared to "real serial".
Another option is to use an Arduino Mega, it has 4 hardware serial ports,
but i think softserial should be ok for your purpose, check the playground to see how it is used.