I managed to get two xbee ZB S2C hooked up. As for the configurations, I have a Coordinator (ID=17, CE=1, DH=0, DL=FFFF, JV=1) and just one router (ID=17, CE=0, DH=DL=0, JV=1).
When I set AP=2 in the coordinator in order to activate API mode, communication from coordinator to router stops (router to coordinator stills works however). I used minicom to read/write in UART ports for test communication.
When you enable API mode on your Coordinator, All data from that point going forward on the Coordinator needs to be in Intel Hex following Digi’s API. Otherwise noting will be sent over the air.
Both of you, if you are using API mode, then you need to send data using the Intel Hex data packet with Digi’s API. For example, if I want to send the word Hello, I would need to issue: 7E 00 13 10 01 00 00 00 00 00 00 FF FF FF FE 00 00 48 65 6C 6C 6F FF
I also managed to send/receive data in API mode using XBee python (https://pypi.python.org/pypi/XBee). Although this library is not well documented, if you download it you can find an “examples” folder which contains useful implementations.