I have an Arduino Mega 2560 with a libelium XBee Shield. If I have an XBee S2 mounted on it and set the two jumpers to the USB setting or remove them, I am able to flash a program onto my Arduino.
However, when I'm mounting one of my XBee PRO S2B (I have three of them available and all behave the same) on the Arduino, no matter how I set the jumpers, it is not possible to flash anything on it. I always see
avrdude: stk500v2_getsync(): timeout communicating with programmer in the Arduino IDE.
Is the XBee PRO S2B incompatible with the Arduino or what might be the issue? I also tried to add an external power source additionally to the USB, but it didn't help either.
After some more experimenting, I found out new details. I tried to disconnect each pin of the shield individually. While doing it, I discovered that disconnecting the
reset pin from the arduino makes it possible to flash it - take a look at the XBee shield schematic, it's pin 5 from the ICSP connector; Photo:
I used a multimeter and discovered that the XBee PRO S2B CTS / DIO7 port is high, while the one from the XBee S2 is low, and so constantly resetting the arduino. I mounted the XBee PRO S2B onto the Sparkfun XBee Explorer USB and opened a serial port with PuTTY. In contrast to the S2, the PRO S2B provides a menu with several options:
B-Bypass Mode F-Update App T-Timeout V-BL Version A-App Version R-Reset >
As soon as I type B, the CTS port goes low, and would prevent the arduino from resetting. Also this mode is needed to detect the module via XCTU. However, with an unmodified arduino, I wouldn't have a chance to send this letter, since the XBee is constantly resetting it. What is this menu, can it be disabled somehow?