can't you just get it's DB value?
This command reports the received signal strength of the
last received RF data packet. The DB command only indicates the signal strength of the
last hop. It does not provide an accurate quality measurement for a multihop link. DB can
be set to 0 to clear it. The DB command value is measured in -dBm. For example if DB
returns 0x50, then the RSSI of the last packet received was
-80dBm. As of 2x6x firmware, the DB command value is also updated when an APS
acknowledgment is received.