Bluetooth Class-1 as a control channel?

[Kaptah]

Does someone have experience in using a higher power (Class-1) Bluetooth module in controlling a UAV? I am thinking of having a suitable control program in a laptop (a terminal program using AT type of commands at least). The ARM7 based UAV controller would then communicate through a Bluetooth Class-1 EDR module. The UAV Bluetooth would have a good quality antenna. Also the laptop would have a USB Bluetooth Class-1 dongle. Through the control link I would see the UAV status (battery, BT link quality, GPS information etc.). Additionally I could send real-time commands to the UAV.

Is Bluetooth as a protocol fit for this kind of environment in which the RF link can fade off rapidly from time to time? What kind of communication range can I expect in free air?

The other option I am thinking of is Zigbee. Zigbee is said to be a lighter protocol than BT. Perhaps it would be more robust to this kind of environment? The link stability is essential. However, Zigbee adds cost, because also the laptop then needs a special USB-Zigbee radio.

[typicalaimster]

The XPS system uses a modified firmware ZigBee-Pro module for their communication. There are a few people out there trying to reproduce their system.

[Arthur P.]

Wouldn't this development kit which includes 2x 2.4GHz transceivers, PIC programmer, and serial interface, be cheaper (USD 103.50) and already have longer range (up to 280 meters) out of the box: http://www.sparkfun.com/commerce/product_info.php?products_id=715

You will still need to have some sort of binding between the two transeivers to prevent interference, but in other respects I think it might provide a lot of freedom to create your own protocol / front end / number of controls / etc.

[Kaptah]

Arthur, the Sparkfun kit in question has a very low TX power. Due to this it would not be capable of stable longer range communication. I was thinking of integrating the communication into a single PCB as part of the UAV controller.

[Unterhausen]

zigbee pro kit seems to be pretty much perfect for a lot of applications. Higher bandwidth would be nice though. It seems like there are new variations on wifi coming down the pike that will also be very nice, but not sure I'd want to use one for control.

[Jack Crossfire]

Would be nice to know how well Zigbee works as a replacement for flight control transmission. It's not optimized for rapidly changing orientation like the purpose built radio sets. It's a lot of work to replace a radio set with custom firmware.

[typicalaimster]

I don't know. There are two threads that I've been watching the development on. One of them is a open source TX using xBee (http://www.rcgroups.com/forums/showthread.php?t=651255) and the other is some guy building his own RC TX. It uses some PIC with a LCD display. Plus I've occasionally popped over and read your RC Terrorism blog, Jack. It seems like people are getting the right idea. It's just a matter of putting 1+1 together.

*edit*
Found the other thread (http://www.rcgroups.com/forums/showthread.php?t=692649) it's by village_idiot

[Arthur P.]

Would be nice to know how well Zigbee works as a replacement for flight control transmission. It's not optimized for rapidly changing orientation like the purpose built radio sets. It's a lot of work to replace a radio set with custom firmware.

On the TX end you might be able to follow the Spektrum DX approach (more power with an opamp after the Tx chip), while on the Rx end, using two RX-s and them have a microcontroler figure out which one is receiving the best signal is an option.

[Kisssys]

I built a Xbee Pro TX RX and would be willing to share the source code and schematics if anyone would like to experiment with Zigbee. You need to buy a development kit which I believe the price is $179. And that doesn't include the cost of the mating RX and TX board. It's worthwhile only it you need total control of the process like I do.

You need to use Zigbee pro modules. I question the future of using Zigbee for RC but it's not hard to do. Their are only 13 frequencies and you probably need to go 2 frequencies over if your having interference on any one. The neat thing is the ability to do telemetry at the same time and that makes it a worthwhile adventure for UAV type of work.

2.4 ghz is a license free. They can do that because the signal doesn't go very far. 900 mhz would be much better. I have not had any control problems with my systems and I fly a helicopter with it without any problems. I question its future because of the unlimited use of the frequency by the millions of zigbee modules that will be sold. Wifi works great until your around a couple of dozen other users then it goes to pot.
I'm afraid that it could be the case for Zigbee.

[mwhazard]

I'd highly recommend the spread spectrum radio modems from MicroHard. They are a little pricey (maybe $500 or so per card) but are worth it for data integrity and range. With 1W 900MHz transmitters, the range is in miles with a low-gain rubber duck antenna, 60 miles line of sight with better antennas. Options include transparent over the air encryption at 230kbps.

I've used their MHX-920 modules. http://www.microhardcorp.com/MHX920A.htm

Matt Hazard

[typicalaimster]

I built a Xbee Pro TX RX and would be willing to share the source code and schematics if anyone would like to experiment with Zigbee. You need to buy a development kit which I believe the price is $179. And that doesn't include the cost of the mating RX and TX board. It's worthwhile only it you need total control of the process like I do.


Sure if you want to shoot them over to me I'd be more than happy to try it out. I've ran across a few PPM to Serial converters out there. Plus I already have the ZigBee's and various other maxstreams in stock.