A handheld MP3 player I'm building on an ESP32-S3. It reads MP3s off a microSD card, decodes them on-chip, and plays them through a MAX98357A I2S amp. There's a 2.2" TFT that will eventually be the UI.
Work in progress. Audio playback works and the display works, but they live in separate sketches right now. Getting them into one firmware with an actual UI is what I'm working on next.
Playback from the SD card through the amp and speaker:
| Component | Part |
|---|---|
| MCU | ESP32-S3 Dev Module |
| Display | HiLetgo 2.2" ILI9341 SPI TFT, 240×320 (has a microSD slot on the back) |
| Amp | MAX98357A (I2S DAC + 3W class-D) |
| Storage | microSD card in the display's slot |
| Power | USB for now, LiPo eventually |
The TFT and the SD card share one SPI bus since the SD slot is part of the display module. Each one gets its own chip select.
| Signal | GPIO |
|---|---|
| SPI MOSI (shared) | 11 |
| SPI SCK (shared) | 12 |
| SPI MISO (shared) | 13 |
| TFT CS | 10 |
| TFT DC | 9 |
| TFT RST | 14 |
| SD CS | 18 |
| I2S BCLK | 17 |
| I2S LRC | 15 |
| I2S DOUT | 16 |
mp3_player.ino— the main sketch. Mounts the SD card, sets up I2S, and plays an MP3 using the ESP32-audioI2S library, which handles the actual decoding.i2s_tone_test.ino— plays a 440 Hz sine wave using the ESP-IDF I2S driver directly. I wrote this to check the amp and speaker wiring before dealing with SD cards and MP3 decoding.display_test.ino— initializes the ILI9341 and draws some text.
(Arduino IDE wants each sketch in a folder with the same name — it'll offer to move it for you when you open the file.)
- The display would not talk to the S3 over hardware SPI. Switching to software SPI (passing the MOSI/SCK/MISO pins explicitly to the constructor) fixed it. It's too slow for smooth UI redraws though, so I still need to figure out the hardware SPI issue.
- SD init was flaky until I dropped the clock to 4 MHz.
- Don't run the tone test at full amplitude. Learned that one the loud way — it's at ~25% now.
- Arduino IDE with the ESP32 boards package, board set to ESP32S3 Dev Module
- Libraries: ESP32-audioI2S, Adafruit GFX, Adafruit ILI9341
- Put an MP3 on the SD card and change the path in
mp3_player.inoto match (it's/music/track.mp3by default) - Upload, then open Serial Monitor at 115200 to see what's happening
- I2S audio out (sine test)
- Display bring-up
- MP3 playback from SD
- Combine display + playback into one firmware
- Song browser on the TFT
- Buttons for play/pause/skip/volume
- Fix hardware SPI so screen redraws are fast
- LiPo battery + charging so it's actually portable