effect selector (display and rotary encoder)

4 years 2 months ago #2099 by yojimbo
Thanks to extra time to get around to some back-burner projects (yay Covid!), I finally built an effects selector for the Pedal-Pi. I like the Pedal-Pi, but wanted a simple way of switching between the effects without needing a terminal. I built this to allow for stand-alone operation of the Pedal-Pi. Definitely not the most elegant implementation, but it does the job. I thought other people might like this as well, so wanted to post here.

I used a tiny OLED display from adafruit that I had laying around (they have an updated version, may not be perfectly compatible with my code). and a rotary encoder. written in python (I'm not much of a coder anymore, so python is the best I can do). I left the c programs for the effects untouched and the python program calls them as a subprocess using subprocess.Popen(). When you de-select the effect, the python script kills the effect using subprocess.kill().

I created images for each of the effects (okay, I think I "borrowed" some of them via google image search), and cycle through the images/effects when you turn the encoder. When you push the button on the encoder you either activate or de-activate the effect shown on the display. Because I didn't change the effects at all, you only get a single effect at a time. I thought about re-writing the effects so you could chain them together...perhaps in the future.

Youtube Video of my effect selector in action

Github for the python program, and images

I still have this running on a breadboard, but am looking to mount this within an enclosure and hard-wire it. If this Covid lockdown goes on much longer I might look to improve further...who knows!

Let me know if you try this. Feel free to make/use/improve.

BTW, is ElectroSmash still active? Looks like there haven't been forum posts in a long time.
The following user(s) said Thank You: Skolnick

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4 years 1 month ago #2100 by Skolnick

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4 years 1 month ago #2101 by Ray
Dear Yojimbo, yes I'm back, first of all thanks for your contribution, I reckon that it is a fantastic idea.
When I first designed the pedal-pi I wanted to use small form factor, so people can experiment and use it as a platform, and that's exactly what you did :)

The project it is working :) :) , so the next step could be to use an enclosure and wire everything, although making the "window" for the OLED could be tricky...
Hammond has a great variety and they are easily available online, they have aluminum and also acrylic boxes, so they are easier to work with, have a look at the most common boxes:


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4 years 1 month ago #2105 by yojimbo
This is such a great platform to play with! I bought the pedal pi as a project to build with my son (14) who is the guitarist. It has been fun teaching him a bit about electronics, signal processing, programming, etc in a way that is interesting/fun to him. Having the ability to switch effects without needing a computer/terminal attached has added a lot to his use/enjoyment of the Pedal Pi.

I'm looking for a better display. The OLED I used is great, Incredibly bright and crisp, and VERY cheap; You can buy off of ebay or amazon for around $5. It is tiny, though, (smaller than 1 inch). If you were to place this pedal on the floor, I don't think it would be readable with this display. Maybe if I kept the graphics simple...
There are a few I2C displays that are bigger, but they are not nearly as well supported or inexpensive.

I haven't thought about housings. I had the stock Pedal Pi mounted in an old ipod touch packaging (clear plastic, and perfectly fit the pedal pi with raspberry pi attached). I just drilled holes for buttons, switch, and power supply. It fit perfectly, and being clear plastic it allowed you to see the guts. I'd like to keep the clear acrylic enclosure, but will need to find something large enough.

If you should ever spin the pedal pi board, perhaps think about bringing out a few lines to a header. The I2C lines and a few GPIO lines would be nice and make it a bit easier to do some hardware hacking. Attaching wires to the pins for the raspberry pi header is not the easiest thing to do, and the results are fragile.

There is never enough time to play around with these things as I would like. I have lots of ideas on mods / improvements / additions, but am time constrained. maybe the next pandemic...

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