Hello!
I'm interested in designing and building my own custom tx and rx from scratch. Although, my electronics (circuits) skills are not quite up to par with this. (Started with computer science first -- just now starting on electrical engineering).
Could anyone point me to some useful resources that could get me started on this project?
I plan on using PCTx to convert from computer to rf and write my own software to interface with telemetry data and control the UAV.
Thanks!
Replies
I have the same project planned. Might have a little more electronics experience.
If you've checked out the OpenLRS project...
http://blog.flytron.com/category/openlrs-project
http://forum.flytron.com/viewforum.php?f=7
They're using a Hope RF module (RFM22B) and a microcontroller. Specs are 100mW @ 433mhz, with 121dB recieve sensitivity IIRC. The module uses an Silicon Labs radio on a chip. The SiLabs chip has 256kbps data rate, 100mW output power, and an amazing 121dB recieve sensitivity. The Hope RF module looks like a little SMT board with the chip and about 27 SMT resistors, caps, and whatnot.
Since OpenLRS uses a SMT motherboard that the module plugs into already I'm not sure why they're not putting all this on one board. The module can only make it cost more. Then again it's not that expensive (about $16 I think) and they're probably getting a good volume discount.
Anyways, I got the idea of using the new SiLabs 1000 (1001,1010, or 1011) SoC (system on a chip). This chip uses the same radio but adds a uC to the mix. Using a SoC radio we should be able to eliminate the separate microcontroller, reduce costs, complexity, and power requirements. The SoC has the same radio specs. Hope RF also makes a module based on this chip (RFM50), which looks like it uses about 35 SMT pieces.
My idea is this... Use the SoC radio chip and a TI TLC5940 16 channel PWM controller chip (serial interface to SoC chip) to make a nice controller/RX/TX board. By offloading the PWM to the TLC5940 we should be able to get excellent PWM control for driving the servos without wasting GPIO pins or clock cycles.
I'm pretty confident we could make the simplest and cheapest RC TX/RX system to date. It would have 100mW @ 433mhz, 256kbps data rate, and amazing -121 dB receive sensitivity. At a bare minimum this should do 1.5 mile+ control and allow 2-way telemetry and commands. This should be an ultra-cheap 2 chip SMT board with plenty of extra features to find a use for.
The radio chip is just awesome! Very low external component count, super low current consumption, 100mW out of the chip, and unmatched receive sensitivity.
My hope is that once a prototype is built we'll find that there is enough computing power and pins left over that we can implement an entire autopilot and telemetry sensor package. That would be the ultimate goal, and if it doesn't work out it shouldn't be that hard to add another uC to do the autopilot/sensors.
In any case it would be nice to build a RX/TX/autopilot/sensor board that can be done with 2-3 chips and a couple dozen SMT pieces. It would be the most modern and cheapest design to date by far. OpenLRS also has a 7W TX module (legal?) BTW, so all the work for an extremely long range system has already been done. 1W seems like a nice round number to me and is probably the most you can legally transmit on ISM bands in the US.
Anyways, all that has to be done is work off the Hope RF modules/OpenLRS schematics and code. We just design a new board using the SoC instead of the 2-chip solution and port the code over. Simple right? LOL
Well, that's my grand scheme for the next gen long range controller system. I need people to help me. On my own it will be completed in about 5 years. But if anyone else wants to use the latest and best ICs to make the simplest, cheapest, best performing system with the most features of anything out there, then post here.
I'm hoping to get a couple Hope RF modules, a SiLabs devkit for the Si10XX, and engineering samples for almost everything else within the next two months. Hopefully I/we can cobble together something for a ground test before X-mas.
Matt,
You might want to take a look at this thread to get an idea of what it takes to build a custom TX/RX combo: http://www.lynxmotion.net/viewtopic.php?f=21&t=4399
I presently have several of the PCTx interfaces and am investigating interfacing the PCTx to a Spektrum DM8 rf module. I believe that the PCTx signal will have to be inverted to work with the DM8 rf module.
This undertaking will not be a trivial task. Good luck.
Regards,
TCIII
Well, if your in the U.S. or its territories, you'll have to comply with FCC rules... which boils down to a very limited range and can only do AM transmissions. FCC: Title 47
There's one or two parts that should apply specifically to your application. If you have a Tx and Rx already, there should be a FCC sticker that says something to the effect of "Complies with section blah blah of part blah blah of Title 47," look for the section and part that's in, and see what you'll be able to do without a license. If that's not enough, well, I guess you'll have to get a license.
You might actually be better off going with the existing technologies first, such as the Xbee's, so as you can get a feel for wireless communications and its quirks.
There's quite a bit on Communications Engineering, which is a subfield of EEEN that looks specifically at the electrical and electronic exchange of data (wired and wireless). It's pretty heavy in Random Signals theory and Laplace domain equations, and is not suggested for those without at least an understanding of Linear Algebra and Fourier and Laplace mathematics.
As far as your circuits goes, Try out Sparkfun.com for part supplies and some instruction on the construction of the electronics.