xbee in API mode resets every 5 seconds with Arduino M0 talking to it via UART

Dear all,

I am currently experimenting with an Arduino M0 clone, the itead studios Xbee shield 1.1 and an xbee s2c with 802.15.4 function set and latest firmware version 2001.

I have reduced my sketch to the bare minimum to show the issue: m0_itead_shield_xbee_test.ino · GitHub

In short, when I send an AT request to the xbee (it's in API mode, because I'm using the xbee-arduino library for functions in the rest of the setup which is not shown in this minimal sample) to read the value of MY (as a test) the xbee does a hardware reset every 5 seconds.

I get no other packets back, except the MODEM_STATUS_RESPONSE indicating that it has just performed a hardware reset.

Any hints and tips would be greatly appreciated!

(at least the RTS signal seems to be working: If I set the RTS pin to HIGH, the arduino gets absolutely nothing back from the xbee, as would be expected.)