I'm trying to communicate with a Roomba 530, but I cannot tell if my pins 0 & 1 serial port is working.
When I have my Diecimila plugged in via usb to my PowerBook I can monitor the serial output of the Diecimila fine. The TX light even blinks.
However, when I remove the usb from my PowerBook, and insert the cable into the Roomba I get no response from the TX light.
Could it be that I have fried part of my Arduino board? How can I diagnose this?
You can use a P4B Serial to TTL adapter from Wulfden / Modern device and connect it to a PC with a real serial port
The TX/RX LEDs are connected to the FTDI chip, not to the TX/RX lines directly. I don't know how they behave when you use pins 0 and 1 instead of the FTDI.
The RX and TX LEDs only flash if you are sending and receiving data through the FTDI chip, not if you use pins 0 and 1.
You could add the LEDs for testing or put them on the circuit board you use to connect the roomba.