You may have noticed that we had wireless telemetry in our flight testing last week. It's really easy to add.
The first thing to keep in mind is that you should use Xbee modules in a different frequency range than your RC equipment.
If you've got 72Mhz RC gear, you can use 2.4Ghz Xbee modules. We use Xbee Pro wireless modules with a Adafruit adapter board on the aircraft side, and a Sparkfun USB adapter board on the ground/laptop side.
If you've got 2.4Ghz RC gear, you should use 900Mhz Xbee modules. We use a Xbee Pro with the wire antenna for the aircraft, and and Xbee Pro with a SMA antenna connector (and a good 900Mhz antenna) on the ground, with the same adapter boards as above.
Next, you need to set up your Xbee modules. They ship with a default of 9600bps, which you must change to 4800 bps for ArduPilot 1.0 or 57,600bps for ArduPilot 2.x. Connect them with your FTDI cable (see instructions here) then use Digi's X-CTU utility to change the baud rate to 4800 or 57,600 (in the modem configuration tab--press the Read button and then click on and change the baud rate line). You should also give them unique Network IDs so they'll be paired. Just use any 3-digit number, and just make sure you've set it the same on both modules. (Don't use 999 if you're going to be flying around me--that's mine!). When you're done with the settings, click "Write". Remember that after you change the baud rate you have to switch back to the PC Settings tab and change the baud rate there, too, or the utility won't be able to communicate with the module. (Switch it back to 9600 when you're switch to the second module, if it's still in the default mode, and repeat the process.)
On the ArduPilot side, use three jumper wires to connect the following pins circled in red on the board below:
--Xbee RX to ArduPilot FTDI port TXO
--Xbee 5v+ and GND to the VCC and GND pins next to the FTDI port.
It will end up looking like this:
(Note: the above is to get telemetry from the Autopilot. If you just want to see the NMEA data from the GPS module, connect the TX pin to ArduPilot's RXI pin, right next to the to TXO pin, instead.)
On the ground side, connect the other Xbee module to your laptop with your FTDI cable, as described here.
That's it! If you open up a terminal program on your laptop and set the baud rate to 4800 or 56,000, depending on which ArduPilot software version you're using, you should see ArduPilot telemetry coming in. Anytime there is a "Serial.println" in the code, that data will be sent through the Xbees to the ground. You can record any data you want, and even GPS datalog from the ground! Couldn't be easier.
BTW, if you want to test the range of your Xbee link, connect the plane-side Xbee module's RX and TX pins together to create a loopback circuit and use the X-CTU utlitity's range test function. For the modules we're using you should get around a mile.
Once you've got the wireless connection set up, you can use our Ground Station to display real-time telemetry with ArduPilot 2.1 and up:
RaWe: You can see my original one flying at the end of this video. It's just an okay flier and is very short of interior space. We mostly just keep it around to impress noobs ;-)
those XBees you recommend look like they have omni antennas. I would have thought the Ground Station would need a directional antenna for a super long range.
You might want to start with the Xbees I recommended in the post. They have built-in antennas, but are best if you're not using 2.4Ghz RC gear. You do need adapter boards on both sides, and a USB cable on the ground side. The cable powers the Xbee.
If you go for the 900mhz ones, which have longer range, I'm not sure where you get the antennas. I've never used that one.
Comments
Can I ask coz I just cant help it, but this question's been always on my mind;
Is there a flying video of your Geo Crawler Predator?
It is certainly a very eye catching platform. How does the performance measure up with your expectations?
regards,
RaWe
those XBees you recommend look like they have omni antennas. I would have thought the Ground Station would need a directional antenna for a super long range.
I'll look into the 900MHz antennas.
Have you done a range test on your xbees? I am looking at getting the same ones, but am not sure of how well they perform.
If you go for the 900mhz ones, which have longer range, I'm not sure where you get the antennas. I've never used that one.
I'm looking for long range downlink telemetry that's easy to hook up to an Ardu.
I'm so new to this that I have to ask some basic questions.
Is there one document that provided the full end-to-end set-up of Telemetery or modem gear, installation & operation?
You've recommended the XBee Pro 900 RPSMA. Do I need 2 of these? One at either end?
What antennas do I use at each end? Do you have recommendations?
How do I power the receiver end & interface to a ground station?
Do you also still recommend use with the XBee adapter board from Adafruit?
Is there some sort of complete bundle or package one can buy that includes everything?
Do I also need the USB TTL-232 cable to interface with the XBee?
I'm almost ready to order everything, but I'm still pretty confused as to what I do and do not need.
I have another altimeter question which I'll post on the main ardu forum.
You help is always really appreciated.
Thanks
Matt
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