• Interactivity

  • Using ADS1115 4 channel ADC breakout board for extra analog inputs

Hi there,

I'm about to start the building phase of my EE senior capstone project, for which I am designing a desktop multi-effects processing box using Bela. My design has 12 input potentiometers, but Bela has only 8 analog ins. To get the extra 4 channels I thought I'd try using a 4 channel ADC breakout board, but I'm confused about how I can refer to my extra analog inputs in the Bela environment. I know I can use the example code (link below) to read values from the ADC, and I know that I'll probably have to run that as a auxiliary task to avoid clogging up the audio thread - where I am lost is how I actually use the values in my main script.

Can I wrap the process of reading values from the 4 channel board in my own version of analogRead? Is it safe to do that inside the audio thread? Do I have to ensure the sample rates match up?

I don't expect concrete answers on these questions, what I need is confirmation that this is/isn't possible and a general framework of how it would be accomplished. Any advice you can offer will be greatly appreciated. My journey with Bela is just beginning but I am so glad to have found it! It's perfect for my project 🙂

https://www.adafruit.com/product/1085
https://github.com/ControlEverythingCommunity/ADS1115/blob/master/C/ADS1115_4Channel.c

Hmm as it happens there are 7 extra ADCs on the board that we are not using. They are 12bit and I think the range is 0-1.8V (or some of them can be 3.3V on BelaMini I think). These are the pins labelled AIN0 through AIN6 here for Bela or here for BelaMini (AIN6 is not usable on BelaMini, but you have AIN7!). You could use those instead, without need for an extra external ADC.
I haven't tried to use them myself, but here you can find an example (check out the "Read ADC" tab in the "source code" section). Be extra careful about the voltages you connect to these pins: they shouldn't exceed the rated voltage for the pin.

You will not be able to read them with analogRead(), nor will you be able to read them from the audio thread. They will have to be in an AuxiliaryTask and you shall read them from there and pass the variables back to render() if you need them (e.g.: with a global variable).

Fantastic, thanks for your quick response. I will look into using those pins instead.