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The XBees replace a wire between the two FIOs. Exchanging data is a simple as Serial.print() on one and Serial.available() and Serial.read() on the other.
How you been successful at getting the FIOs to exchange any data? If not, start simple(r).
I don't know if i need to change configuration of each xbee to communicate to each other (with FIO XBeeConfigTool) or are they already set up to use point to point without configuration.
Digi claims that you don't, but absolutely nobody has posted on the forum that they have been successful at getting two ransom XBees to talk to each other without configuring them.
You need to set MY, AL, and PAN ID at a minimum. MY on one XBee must be the same as DL on the ther other XBee. The actual value doesn't matter, as long as it is not 0. PAN ID must be the same on each.
Where is my mistake???
Not having a USB explorer. Having one is money well spent, believe me.