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NexoBT

Created by [Giacomo Rossi - @giacomo] β€’ Started on May 28, 2025

Bluetooth receiver based on an ESP, fitted on my own PCB design.

DAY 1 - 19/06/2025

  • Today I started creating the PCB, more specifically the power supply: It will be a diet with 2 voltages, one at 5v atraverse a connector to Barrell Jack, an interruption a status LED and several filter capacitors, the other at 3.3v useful for the ESP obtained at the time the use of an AMS 1117 - 3.3. Schematic with power supply
  • I started thinking about that ESP 32 module to use, I think it is for one with SMA lactacco to use the external antenna.
  • I decided that for the audio output I do not use the TRS or XLR connectors but of the bipolar connectors so that both types of peripheral can be connected like this: XLR / TRS 6mm bipolar conerger
  • I evaluated the use of an DAC and I came to the conclusion that it is a necco but I still have to understand which one and how to choose it.

DAY 2 - 29/06/2025

  • I continued by deciding which components to choose:
    • Bluetooth processor / receiver-> ESP32-WROOM-32UE-N4
    • Dac anchor to choose from even if I think I choose the PCM 1793 or the PCM1794
    • I have the doubt because I have to better understand how differential outputs (balanced) work with these chips.
  • I therefore started creating the schematic for the ESP chip: Schematic Esp Chip
  • I also wired the audio outputs: Schematic Audio outputs

DAY 3 - 04/07/2025

Maybe I should continue this project more often I'm carrying out a little too little :/ * I completely changed my mind on the dac to be used (thanks to the advice of @AAVOJ :D) * I use a Max98357a very simple to use and incorporate an amplifier that greatly simplifies the design and makes the PCB cleaner - Use 2 chips one for each channel - I prepared a selector for the gain that can be moved via a jumper - to select the Visogna channel, set the SD_Mode iìcon Pin a resistance on the right channel while the accident must be high Schematic MAX98357A * with the ESP32 processor I still have to understand how I go ahead I'm still stopped * I am at a good point Yuppyyy I think the next few days I stop (I have an amnesty exam for the super important university :) ) but I promise it. * Today the state of the schematic is as follows: Schematic_2025-07-04 *I'm assuming a screen but I don't know :/