I have several questions about the 3DR radios that I was hoping some developers might be able to answer to facilitate my thesis research...
 The 3DR wiki says 8 parameters must be the same for two 3DR radios to communicate, but I cannot find a fixed possible parameter value for two of these parameters (firmware version & LBT_RSSI)... can there be an infinite possible values for these parameters?
 I've tried using AT commands in the Linux terminal to change the values of these parameters, but I am getting no response at all from the 3DR ground-module... what are the proper Linux terminal commands (or other process, e.g. bash scripting) to modify individual parameters of the 3DR (USB) ground module?? Here's what I tried that elicited no response from the 3DR ground-module:
user@linux:~/MAVProxy# stty < /dev/ttyUSB0
speed 57600 baud; line = 0;
min = 0; time = 0;
-brkint -icrnl -imaxbel
-isig -icanon -iexten -echo -echoe -echok -echoctl -echoke
user@linux:~/MAVProxy# echo "+++" > /dev/ttyUSB0
user@linux:~/MAVProxy# echo "ATi" > /dev/ttyUSB0
user@linux:~/MAVProxy# echo "ATI" > /dev/ttyUSB0
user@linux:~/MAVProxy# echo "ATi5" > /dev/ttyUSB0
user@linux:~/MAVProxy# echo "ATI5" > /dev/ttyUSB0
user@linux:~/MAVProxy# echo "ATi+++" > /dev/ttyUSB0
 Could a 3DR ground-module be used to manually broadcast a heartbeat message? (e.g. using the the 3DR radio as an interface for Scapy to broadcast the MAVLink heartbeat message with rapidly changing & widely varying GPS data)
I would immensely appreciate answers to any/all of these, is it will greatly aid in conducting my experiments... THANKS!
I'd recommend you install and use mavproxy on Linux. Do this:
apt-get install python-pip
pip install pymavlink mavproxy
The to connect to the radios use:
mavproxy --baudrate 57600 --master /dev/serial/by-id/FTDI* --setup
then use +++ followed by enter to get the OK prompt
and follow the rest of the commands from the docs
Re your other questions. Firmware version is a 32 bit number, so 4 billion possible values. LBT_RSSI can only be in the range 0 to 255.
The 3DR radios are point to point, and don't currently have the concept of a broadcast.