Author Topic: Blackaddr/Teensy based pedal build  (Read 484 times)

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audioartillery

Blackaddr/Teensy based pedal build
« on: April 06, 2018, 12:16:10 AM »
A friend and I have been talking about getting into DSP effects for a while and recently picked up a couple of Blackaddr's "Teensy Guitar Adapter" boards (I'm just going to refer to them as "Blackaddr boards").  I figured I'd do a build thread as we go along since I don't think many people know about the Blackaddr boards.

This pedal is primarily intended to be a developer platform for our needs.  So it's big, has lots of knobs, and a small OLED display.  We settled on the Hammond 1550G enclosures (roughly 8.5" x 5.75").  They're huge but I didn't want to get backed into a corner since the Blackaddr boards while electrically quite sound aren't really designed to cram into tight spaces.

Here's what I've modeled up so far:





I opted to put the Blackaddr board upside down since it's got quite a bit on its underside (which I haven't modeled in any detail) and mount it by its 1/4" jacks.

With 7 knobs, 6 switches (the knob by the display is also a button), and an I2C display we are way, way out of bounds from what the Blackaddr board brings out to its headers.  It has 8 pins that it exposes from the Teensy and only one of those is an analog input.  So I'm going to use an analog mux for sampling all those inputs.

I found some Neopixel type LED's in a standard 5mm "hat" LED form factor which I'll be using for the indicators since we would otherwise be short one pin.  I may throw some more LED's on there somewhere.

[Note:  there are lots of pins on the Teensy that aren't exposed, we could tap those if needed. Im trying to make this easy plug together. ]

Well that's all for starters. Oh, well, one concern I have is the Teensy will be quite busy doing audio processing. Im a little worried about it driving Neopixel protocol which also has a real time requirement. Worst case I think I just drop another Arduino of some type in the box and hook it up on the I2C lines.
« Last Edit: April 06, 2018, 12:22:55 AM by audioartillery »

ElectricDruid

Re: Blackaddr/Teensy based pedal build
« Reply #1 on: April 06, 2018, 05:57:21 PM »
Crazy stuff! I shall keep an eye on this. Good luck!

Tom

audioartillery

Re: Blackaddr/Teensy based pedal build
« Reply #2 on: April 09, 2018, 09:23:07 PM »
Some minor progress while I wait for our enclosures.  I've been wanting to build up some skills designing PCB's so I've designed this fairly simple board to route the various inputs from an analog mux to the BlackAddr board.



One of these analog mux boards will socket into this.  I haven't decided on a clean way of mounting this, but I think I can just 3d print a bracket that mounts in there somewhere convenient.

audioartillery

Re: Blackaddr/Teensy based pedal build
« Reply #3 on: April 14, 2018, 03:51:50 PM »
PCB's should be arriving next week.  In the mean time, did a little test with these programmable LED's.  If you aren't familiar with them, they're usually referred to as NeoPixel type LED's (WS2812 is the underlying chip/protocol).  You can get them in flex circuit strands, grids, rings, etc.  For this project I'm just using them for the foot pedal indicators.

They use a single wire protocol so they just get chained together.  I'll probably cram a few more of them in there some place just because they're cool.

Here's one of mine in action:


Blackaddr

Re: Blackaddr/Teensy based pedal build
« Reply #4 on: April 15, 2018, 09:33:57 PM »
This is looking pretty cool!

If you find that you want to separate the control processing (switches, knobs, leds, etc.) from interfering with the audio processing, take a look at the Teensy LC. Dirt cheap, very small, ideal for handling low-speed stuff that needs interrupts or polling that might interfere with the main Teensy doing DSP work as smoothly as possible.

If you don't mind my asking, what software are you using for the modelling?
« Last Edit: April 15, 2018, 09:40:26 PM by Blackaddr »
Blackaddr Audio
Digital Modelling Enthusiast
www.blackaddr.com

audioartillery

Re: Blackaddr/Teensy based pedal build
« Reply #5 on: April 15, 2018, 10:34:28 PM »
Fusion 360 for the 3d modeling, KiCAD for the PCB.

Yeah my fallback plan is to put down another board/processor to handle I/O and leave the Teensy just for audio processing. My understanding is the Teensy has a DMA based neopixel library which is the only real-time thing I need to do besides process audio.

The Teensy LC looks super tiny. Id probably use a Blue Pill board since Ive got a few of them and theyre like $2.

audioartillery

Re: Blackaddr/Teensy based pedal build
« Reply #6 on: April 20, 2018, 12:45:02 AM »
Got the PCB's back today.




I spent some time trying to get an I2C device talking on the SCL2/SDA2 lines that are brought out to the BlackAddr external header (which I've broken out on this PCB).  Can't seem to get the Teensy advanced scanner to work with the Wire2 bus, it just times out.  I'm pretty new to the Teensy ecosystem so it may be something I've overlooked... seems like it ought to work though.