Just a quick question. Can I send serial commands from the rx, tx pins without the FTDI chip.
Im trying to setup a thermal printer to print off stored GPS coordinates from an onboard SD card. But I don't need it connected to a computer through its serial port, I just need it to receive from the atmega1280 chip.
Yes, digital pins D0 and D1 are the (hardware) serial pins of the AVR. More important is what the serial interface is to the thermal printer: digital levels (0V/5V) or RS232 levels (-10V/+10V). Do you have any information on this interface?
You can also use the NewSoftSerial library to use any digital I/O pins for low-speed serial communications.
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The FDTI pins are isolated from the 328's TX and RX so you should be OK, but if you are downloading sketches the printer will see whatever the 328 says to the FDTI and do it's nut. You will probably have to disconnect the printer or turn it off while programming the Arduino.