How do I send At commands in API mode using a pic chip

Sending AT commands in API mode is just a matter of constructing the API frame and sending it out your serial UART. First I would read through the manual for your radio and double check the format of the AT command API frame.

You can also use the frame maker ( to see how to put together the frame.

Next you just need to program your PIC chip to send the bytes of the API frame to the XBee. I am no expert in PIC programming but there is a guide I found online that could help.