XBee Wifi on Mega IO Expansion Shield

I have an Arduino Mega 2560 R3 with an IO Expansion Shield v1.1 (Arduino Shield List: DFRobot Mega I/O Expansion Shield V1.1) and an XBee Wifi module. I tried connecting to the XBee with X-CTU without success. I also tried using the XBee Wifi code at GitHub - cjbearman/xbee-wifi-spi-arduino: Arduino library to support Xbee Wifi modules, using SPI communication, but I don't know what the pin assignments should be for XBEE_RESET, XBEE_ATN, XBEE_SELECT, and XBEE_DOUT. Do I need to make modifications to the Mega or Expansion Shield to get this to work or is it purely a software issue? What pin assignments should I use in cjbearman's code or is there other code out there that I could try?

I think I figured out the problem. I have the S6 Wi-Fi module, which requires an extra capacitor to handle the in-rush current requirements. I’m sending it back in exchange for the S6B, which doesn’t require any board modification. I’ll post again when I’ve tried it out.

I got the S6B in the mail today. I wrote a blank program to the Arduino, connected the 9V adapter, connected the S6B, and I still can't get it to connect in X-CTU. I measured the voltage of the Vcc pin and it reads 3.3V even with the USB cable connected so that is a good thing. I don't know what else to try.

If the XBee uses the SPI bus, then that shield is using the wrong pins. The SPI bus is not on D11-D13.

Yes, the SPI pins are not connected. I should be able to use the UART to communicate with X-CTU and the Mega, but I'm still at a loss as to why it's not working.