Raspberry Pi as robot controller

Technical Control System
1

I wonder how well this would work, the raspberry pi does have the processing power to do this, and the gpio could do the interfacing.

This is just an idea, up for discussion, What do you think?

2

Well when I get mine, I’m planning on having it talk to an arduino (which may or may not talk to another arduino) and do some localization/vision processing/dead reckoning/video feedback.

I don’t think the foundation technically supports any RTOSs for the pi, and I’d be weary controlling a robot during the time when the cron jobs start running (or whatever)

3

Linux is perfectly capable as an RTOS. A system patched with RT_PREEMPT (which has ARM support) would have more than sufficient realtime for our purposes.

Just wanted to clear that up.

4

Yea especcialy with the gpio pins it could have a lot of potential in the robotics community

5

The Pi itself is pretty lame as a robot controller. The GPIO pins are all 3.3V, and there isn’t any analog IO. That’s not to say you couldn’t build a cool shield/cape/extension board that would give you a lot of robot control functionality, and people are working on it.

The idea of having my robot be a full-blown Linux box is pretty appealing. I think I’d take the new Vex ARM9 controller (which also runs Linux) over the Raspberry Pi when it comes to robot functionality, but it’s hard to beat $35. :slight_smile:

6

Lots of people in the Raspberry Pi forums are working on this. I bought three Pi’s to play with, and am progressing a little at a time, adding functionality necessary to make a Pi a viable robot controller. (I’m a mechanical engineer, not a software guy.) I hate to advertize my future plans, because the web is full of people announcing big plans with no follow through. But, to date I have been successful in using the Raspberry Pi to control a Jaguar and a servo using a joystick as an input device. With no additional hardware, you can control up to 8 PWM channels. Adafruit sells a $15 accessory board from that lets you add 16 PWM channels at a pop. And it’s only a matter of time before other inexpensive boards hit the market allowing for analog and digital I/O.

Video of joystick control here: http://www.youtube.com/watch?v=0ODQY2mDYR0

7

How are you generating the PWM signal to the Jag and servo? Is it one of the following, or something else?

  • does the Pi have built-in hardware support for generating PWM signals on the GPIO pins so all you have to do is configure the period for each channel and then provide a pulse width for each channel?

or

  • continuously poll a clock and turn GPIO on/off for each of the two PWM channels as appropriate based on the respective joystick inputs

or

  • use a fixed-period interrupt with a counter and a state machine to turn GPIO on/off to turn the GPIO on/off

or

  • use a fixed-period interrupt (at the desired period of the PWM) which turns the GPIO on and then enables a one-shot interrupt to turn the GPIO off

or something else?