Garbage Response to Every Command

I have an LTE Cat 1 Verizon, and I’m using an Arduino Due as a USB-to-serial converter for communication. That setup worked fairly well until the XBee stopped giving correct responses to commands. Now, if I send anything over serial (including +++, any AT commands, and random characters), it responds with a three-byte sequence: 0x1C 0x1C 0xFC, or sometimes that sequence twice. I see no correlation between the input and whether the sequence is sent once or twice.

I’m not sure what would have caused this. I changed the BAUD rate to 115200, but otherwise I don’t believe I made any configuration changes recently.

I tried entering command mode by sending a serial break for 6 seconds, but that appeared to have no effect (the BAUD rate is still 115200 and I never got an “OK” indicating the device moved to command mode).

I also tried a factory reset with ATRE followed by ATWR, but this appeared to be ineffective as I don’t get a valid response to any commands.

I have not used this interface for the XBee cell products. Does it provide the almost 2A of current needed to power the XBee up?

Are you able to use an XBIB-U-DEV (Rev F or above) similar board?

The Arduino doesn’t, but I’m using an external power supply for the XBee that does.

I don’t have an XBIB board, so that isn’t an option.

When you changed the baud rate, did you change it on both the XBee first and then your Arduino? What you’re describing sounds like baud rate mismatch. Unlike a modem the XBee does not auto-baud.

I was wondering about that, but when I change the Arduino to a different baud rate (say 9600), I get no response from the XBee at all.

You may need to use a logic probe or scope to capture the XBee signals to determine what baud rate it’s using, and what baud rate the Arduino is using. You might be in the bootloader – try sending a few CRs or ‘V’ at 57600 to see if you get a response.

Also, I believe that when holding break for 6 seconds, the module may enter the bootloader instead of command mode, depending on what’s connected to the RTS pin.

And, there’s a chance that using break to enter command mode will also default to a different baud rate (9600?). You’d want to check the documentation on that.