xbee s1 with sparkfun regulated board not sending data from pixhawk

XBee & XBee Gateway XBee - 802.15.4
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1

I am using Xbee s1 , with SparkFun XBee Explorer Regulated,
I tested the peer to peer communication between two Xbees , mounted on usb explorer board, and they work just fine tx and rx both way.

then I tested one with 3,3 v i\o fdti cable connected to the xbee on the regulated board, and it works just fine (communicate with the one on the usb explorer board)

then I connected the ftdi directly to the pixhawk uart , and tested that I get data from it. ( again , works just fine)

but when I switch between the ftdi cable to the xbee on the regulated board, it sends nothing !!!
I was able to verify that the pixhawk do revive the data coming from the Xbee on the usb explorer board.

so what can be the problem???

2

What baud rate does your device run at?

Have you set the XBee to match the baud rate of the device?

Does the Pixhawk operate at 3V or 5V?