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Just a quick guide outlining how to interface Paparazzi with the Maxstream 9xtend series of modems.



****IMPORTANT Before you start ensure you have adequate electrostatic discharge (ESD) gear.****

You will need the following hardware:

2 x Maxstream 9xTend OEM modules.

2 x  Breakout boards (sparkfun part # BOB-09596)

1 x Breakout board for USB to serial (Sparkfun part # BOB-00199)

2 x 900Mhz antennas. (i am using Sparkfun part # CEL-08347)

1 x external power supply.

Assorted break away male and female headers (Sparkfun part # PRT-00115 & PRT-00115)


I will only describe how to wire everything up on the ground station side of things as your airborne configuration will be highly unique to your UAV setup.  Once you have completed the ground station configuration you will be able to easily work out how to put your modem into your plane and connect it to the Paparazzi board. There will be no software changes on the Paparazzi ground station or airborne code other than that outlined here for default modem protocol operation. This guide assumes that you use the default Baud rate on the 9xTend modem.


Ground station:

Goal: to connect the 9xTend to the ground station computer via USB.

Firstly solder your 9xtend break out board to your 9xtend. The silk screen should be facing towards the modem.

Next insert your male header pins and solder VCC to SHDN pin this is the modem will always be on as soon as power is applied. For more information regarding the SHDN and how to use it you can consult the user manual.


Next using your USB to serial breakout board create the following connections

TX on the USB-Serial is wired to the DI pin on the 9Xtend.

RX on the USB-Serial is wired to the DO pin on the 9Xtend.

GND on the USB-Serial is wired to the GND on the 9Xtend

Explanation: The data that is leaving the USB-Serial board (TX = Transmit) is entering the modem (DI = Data In) so that it can be transmitted and the data that has been received (DO = Data Out) by the modem needs to enter the USB-Serial board (RX =  received). As we are using TTL logic for data transmission a common ground is used between the two circuit boards so the Ground pins(GND) must always be wired together.


You can now wire your VCC and GND to a 5V power supply i am using a 240VAC - 5VDC mains adapter.


You can then mount your hardware in a box so its nice and protected for when you go to the airfield.


On my plane i am using a Millswood Engineering Failsafe Device which also doubles as a mount and power supply for my 9Xtend. Use the information above to create your own airborne setup.


This guide should get you started if you feel you need clarification of anything send me an email via the contact page.

Tagged in: UAV , Paparazzi , OEM , MaxStream , long range , How to , ESD , 9xTend , 900Mhz , 1W