• How hard can it be?

    Jacob David C Cunningham • 11 hours ago • 0 comments

    So my friends who ride motorcycles asked me about making some hardware for them. You can see that these are just off-the-shelf breakout parts. I'm still not at a phase yet where I can design my own circuit boards.

    Anyway I had a Seeeduino lying around and a BLE module that I bought a long time ago and never used plus an Adafruit speaker... I thought I could just put these together.

    Then yeah I found out it takes more than that to make sound. Or at least what I was after. So I got myself an ESP32, one of the big dev kits.

    And got to this... then I realized the sound was terrible using the internal DAC of the ESP32... so that made me buy an external DAC (purple board a PCM5102) and an amp (green PAM8403).

    Then while it was pretty straight forward to flash a bluetooth sink (A2DP speaker) sample code, this was not enough for what I wanted.

    So I landed on Atomic14's sample code regarding HFP. This became even harder to do. I had to figure out how to compile the code (setup ESP-IDF with bluekitchen bluetooth stack).

    Eventually I realized I had to go back in the past and use versions of the above software to get his code to work which is about 4-5 years old eg. Python 3.9.

    Anyway I got it to work as far as showing up and being recognized as an HFP device... even seeing the mic show up in Audacity however I never actually got sound out of the mic when trying to record from it.

    I did test the mic on its own regarding being electrically connected. The mic I used is an INMP441.

    But yeah it was an eye opening project. I hadn't worked with BT audio before. I ended up making two of them although I don't think it's actually done yet software wise.

    Funny I only now realized I forgot to put a boost converter on the 2nd one. I was in a rush to make them. It's a good thing it works on 3.3V too. I verified that the board worked functionally but I did remember I had to charge it up before it would work, thinking it was just a low battery.

    Also realized another mistake the switch should have gone between the BMS and the lipo, I've made quite a few of these battery charger/boost up circuits before and usually get it right.

    https://m.youtube.com/watch?v=aJC0TfJXg98