Let's Make Robots!

RasPi and RC


This is a bit of a repetition of a question I added to this post, but I tought I'd repost as I don't think anyone will see the other.

I've managed to get my hands on a raspberry pi, and I was wondering; Is it worth using for a transmitter, or would I be better off using a standard microcontroller? Could it handle working in real-time? Is it possible to output PPM on one of the GPIO pins, or would I be better off using a secondary microcontroller?

If I use the pi, how hard would it be to strip back the OS to just run the RC program, so it will boot and run quicker?

Also, does anyone know what the best (and cheapest) way to connect a small phone-type LCD to it? I know that it's got a DSI connector, but I don't know whether that is usable at the moment.

I know I'd need to connect at least 4 analogue inputs to it (probably more like 6), so what's the best way to do this without eating too much into my pins? I'd probably want to add about the same amount of toggle switches and stuff, too.


More info


If possible, this is what I'd like to wire up to the pi;


A PPM transmitter module (extra questions: 1; could I connect 2 types to the same pin, and then select which type by switching the power to the modules on and off, or would this cause interference?  2; could two 2.4ghz modules (one in use, one switched off) share an aerial without problems, or would I be better with 2 seperate aerials?)

A display (Monochrome, preferably graphic)

Probably about 6 anologue inputs (2 sticks, and 2 extra pots)

Probably about 6 toggle switches

Display input; Ideally a rotary encoder (jogwheel), although probably a few push buttons

Possibly a space for an xbee-type radio

Serial in, for telemetry from the transmitter module


These are what I've thought of so far. Any links to information about interfacing to these would be really useful.

One more question; although I probably won't be doing a project like this for a while, would the Pi have the grunt to work as a groundstation for a UAV/UGV (probably based around the ardupilot setup)?

Thanks in advance.

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Sorry, I was meaning one like with an interface like this one. I know these work with the pi (there's a tutorial on adafruit's website), although I'm not sure about the nokia-type graphic ones.

Standing back and letting your idea sink in for a few days, says to me that maybe if remote control builders could get a hold of a computing platform of the RPi size and cost,  they would find a way to incorporate it into their design. I personally can't imagine how having a SBC in a transmitter can be used/useful, but, that doesn't mean there isn't a way.

Re: PPM. Why are you considering PPM when you will be working on your own TX/RX setup. Unless you are transimitting on standard RC frequencies, I would believe that you will have to have your own receiver in whatever you are controlling. That being the case, it shouldn't matter how you send the data to the receiver as long as it is error corrected.

Re: dual transmitters. Are you considering using different technologies that transmit in the 2.4Ghz spectrum?

From the requirements you have mentioned so far, it would seem a standard microcontroller could handle everything you want to do (for now). It looks like a PICAXE 40x2 should have all the I/O you would require to accomplish your current task, as you lay it out.

I have even seen a remote control setup that used a joystick and an xbee as the base and then the vehicle had the other xbee and a microcontroller. The xbee's have digital I/O pins and to a point could be used to probably control a display of some type, as long as they got the proper data from the microcontroller on the other end of the line. :)

Thanks for the comment. I'll try and work through and answer your questions. Forgive me if my reasons don't make sense.

1;same as the answer to 4.

2; I'm considering using PPM as I'll probably use an already-availiable transmitter/reciver setup, at least at the start. I'd like to use something that's allready availiable as; 1, I'll be using this at an RC club, and don't want to cause interference. A ready-made transmitter-reciver setup will be designed to avoid this, wheras an XBEE-type system may not be. 2, With the systems I'm looking at using (FrSky/Flysky), the recivers are cheap, and small. As of yet, I don't think I can manage to manufacture something suficiently small, or for similar/less cost. This doesn't mean I'm not going to try, but that would be a bit more of a separate project.

3; Simple answer here. Although this is just an idea I've been throwing around, I may want to be able to switch between the FrSky and FlySky modules as the flysky ones are cheap, but the FrSky ones have telemetry etc. and are more reliable.

4; I may yet use a standard microcontroller, it's just that I have a Pi, and I'd be intrested to see if I can get it to work with it. the pi has more processing power, so I can use it for more advanced things like, (possibly) acting as a UAV ground station, graphing/recording/analysing telemetry data, etc. I'm still just flinging ideas around here, and trying to come up with a plan.

At Campus Party some guys from the UK showed their Raspberry Pi robot. They use an expansion board with a PCF9685 I2C PWM controller to get more PWM channels to control servos and motors.

More infos here:


Thanks for the link. I don't need to drive servos from the board for this project, however the site looks really useful. I might yet use it to make a robot...