DIY Stompboxes > Digital & DSP

So ya wanna build a High Def Raspberry Pi based multi-effects unit?

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treefall:
Over a year ago I set out to do that.  I found modep which ports the opensource MOD (MOD Devices) pedalboard software to Raspberry Pi.  Wasn't too long before I had a prototype with 24-bit/96khz audio, 4-cores of CPU allowing a dozen or more of the 350+ LV2 plugins to run in a virtual pedalboard.  It sounded great and I could string together virtually any pedalboard imaginable.

I wanted a stage worthy device though, so I added an LCD along with assignable footswitches, knobs, expression, midi, even phone control (via osc)

I shared it with some friends who loved it and it soon became obvious, I should share the project with others.  After many prototypes and issues trying to get enclosures made, I'm making it available to other DIY pedal builders.  Two others have built it successfully so far.  Two more have ordered parts.  I'm looking for 7 more builders before I order another round of circuit boards.

You can check it out the details here: https://treefallsound.com
 


Here's what that pedalboad looks like through the MOD web UI (connected via wifi):


Marcvv:
Wow, Rand, this looks amazing. What an investment you made in the project itself but also your website about the pedal. i might be interested in building one. The website shows the store but there is no price and shipping info?

Cheers, marc

potul:
This is a very interesting project, very similar to an unfinished project I have myself in a drawer.

Although I will probably start tinkering with it, I'm not interested in the whole enchilada kit. I already have a bunch of parts I will reuse and I'm not yet interested in the enclosure (I already have a stage worthy HX Stomp, I want this just for the fun of DIY).
Any chance to get individual parts instead?

My first intention is to test the whole thing with parts I have laying around, and if I'm convinced I might go for the "ready to gig" version. I'm evaluating what parts I can reuse..... so I have a couple of questions:

-Will it work with a model B board instead of the model A+? (aside from the form factor)
-Are you using the touch buttons of the Pimoroni display for something, or can I use another I2C/SPI display instead?
-Any specific reason you are using the Audioinjector audio board? Any experience with other audio boards?
-Are the encoders connected directly to the GPIO pins of the Pi, or is there any interface in the middle?
-Is your custom sofware all programmed in python?





--- Quote from: Marcvv on September 12, 2020, 02:09:12 AM --- The website shows the store but there is no price and shipping info?

Cheers, marc

--- End quote ---

If you click the banner you will go the the product details. 88$. No shipping info though

Marcvv:





--- Quote from: Marcvv on September 12, 2020, 02:09:12 AM --- The website shows the store but there is no price and shipping info?

Cheers, marc

--- End quote ---

If you click the banner you will go the the product details. 88$. No shipping info though
[/quote]

Ah, i missed that. Thanks

treefall:
Thanks for your interest.  Below are some answers...


--- Quote from: Marcvv on September 12, 2020, 02:09:12 AM --- The website shows the store but there is no price and shipping info?

--- End quote ---

Sorry I didn't make that more obvious.  I will.

There are two sets of parts you'll need to build a pi-Stomp.
1) Commodity parts from Mouser.com. The wiki includes a link to the BOM.  The current price for that is $106
2) The pi-Stomp custom parts (Circuit board and enclosure) and parts that Mouser doesn't carry (footswitches, audio card, LED halos, etc.)  My bundle on treefallsound.com is $88.  Shipping is USPS flat rate within the US and should be around $8.60

So bottom line.  Look to spend about $215 to $220 depending on shipping and taxes.



--- Quote from: potul on September 12, 2020, 04:27:22 AM ---Any chance to get individual parts instead?

--- End quote ---

I'll likely offer that eventually, but understand it's not my mission to be a store.  I created a store to offer the custom circuit boards and enclosures but realized to save others from souring parts from 4+ locations and incurring shipping with each, I could stock those parts myself and allow builders to just make 2 orders (Mouser and Treefallsound).  I'm currently offering everything at cost to get people to build a pi-Stomp.  Everything on my store except for the circuit board and enclosure can be purchased from guitarpedalparts.com, smallbear-electronics or amazon.com

If there is demand for specific individual parts, I'll certainly try to offer that so lemme know what you'd like.



--- Quote from: potul on September 12, 2020, 04:27:22 AM ----Will it work with a model B board instead of the model A+? (aside from the form factor)
-Are you using the touch buttons of the Pimoroni display for something, or can I use another I2C/SPI display instead?
-Any specific reason you are using the Audioinjector audio board? Any experience with other audio boards?
-Are the encoders connected directly to the GPIO pins of the Pi, or is there any interface in the middle?
-Is your custom sofware all programmed in python?

--- End quote ---

I appreciate you wanting to build your own hardware.  All of the pi-Stomp specific software/firmware is python and designed with the idea that the hardware platform might be different.  All major components (footswitches, encoders, pots, LCD, etc.) have classes which can be instantiated (or not) or subclassed (https://github.com/TreeFallSound/pi-stomp/tree/master/pistomp).  Theoretically, you should be able to create your own python module for Your hardware in place of 'pistomp', and replace the 4 corresponding import references in https://github.com/TreeFallSound/pi-stomp/blob/master/modalapi/mod.py

Yes, pi-Stomp works great with a model 3 B board.  The A+ was chosen to fit inside a smaller enclosure.  It'll even work with a Pi Zero, though in my experience, with a single core and slower clock speed, it'll start to choke with more than 3 or 4 effects in a pedalboard.  Still, pretty cool and compact.

The touch buttons on the Pimoroni LCD are not used.  You can use other SPI displays and you'll notice in the github repo, I have basic driver subclasses for 4 other displays that I tried.  The pi-Stomp circuit board includes pads for a 10 pin header for connecting an alternate LCD.

I chose the Audioinjector Zero for two main reasons.  Form factor and because there really aren't many cards available with audio in (ADC).  The other two I found at the time both worked fine:
1) AudioInjector Stereo (larger, more expensive, no real advantage other than it comes with a stackable header and volume controls (oddly mounted perpendicular to each other)
2) HiFiBerry DAC+ ADC.  It worked just fine, but at nearly 3-times the cost and twice the size...
Note that the AudioInjector from treefallsound.com has a 2x20 header pre-installed.  If you buy from amazon, etc. you'll have to get and install your own.

The encoders incorporate two switches (the rotary switch and the push switch).  The rotary switches are connected directly to GPIO pins.  The push switches are go thru the Control ADC which is used to interface with the analog pots ("Tweak knob" and Expression pedal).  I did this because I found I could mitigate switch bounce issues better going thru the ADC versus direct to GPIO (and I was running low on GPIO pins but had 6 spare ADC channels ;-)


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