[Noisebridge-discuss] Shouldn't we all hack something ?

Casey Callendrello c1 at caseyc.net
Wed Apr 2 17:14:36 UTC 2014

On 3/27/14, 10:13 PM, Henner Zeller wrote:
> <hacking>
> Back to hacking. This is part of what defines NB and we should all do.
> So after this way to long preamble, I am telling you what I am hacking
> right now.
> Over New Years' eve, I was playing with the Beaglebone PRU to generate
> nice, realtime-clean stepmotor steps
>   https://plus.google.com/u/0/+HennerZeller/posts/HyDMSHRBBDH
> Was easier than thought, and works quite well
>   https://www.youtube.com/watch?v=hIEY9077D64
> Since that worked well, I designed a board together with Jake that we
> call 'Bumps'
>   https://plus.google.com/u/0/+HennerZeller/posts/CS9fhJx9bpX
> They arrived in the meantime (OSH-Park is has a nice quality!)
>   https://plus.google.com/u/0/+HennerZeller/posts/UVa9mFV6z1k
> ... so hopefully on the upcoming weekend we'll find some time to
> solder them together. For that, there is the plan to use Jakes 3D
> printer/dispenser (he did a 5MoF on it) and dispense solder paste on
> the board. For that I wrote a quick program to convert some KiCAD
> output to GCode for doing the dispensing action. Here is the code for
> that:
>   https://github.com/hzeller/rpt2paste
> </hacking>
> -h
Oh, yeah, I saw your PRU code and got super excited! A friend and I are
trying to build an autonomous RC car. We are using the raspi but I'd
really like to switch to the beaglebone.

A critical part of the project is the speed control. The input is a
fixed multiple of pulses per rpm, and the output is a servo-style
signal. I'd like to write a PID controller that handles this. Thoughts?
Is it going to be a big pain? Pulses are at about 100 Hz. My idea was to
put this in the PRU for more precise timing. That way, the Beagle CPU
could handle the the vision side of things.


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