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An RFID story and sound box for the ESP32-WROOM-32: 4 MB of flash, no PSRAM. Inspired by ESPuino, rewritten to fit those constraints.
- One RFID tag → one folder of MP3s on the SD card, played in a loop.
- Branching stories: one audio clip per node, the next one picked with the buttons. Content written ahead of time, no network at run time.
- WS2812B strip: VU meter during playback, one hue per tag, one colour zone per story choice.
- Web configuration portal, in English or French, to bind tags without a serial console.
- A music-box jingle at start-up, synthesised and embedded in flash.
- 18650 battery gauge read from the discharge curve.
| Peripheral | Signal | GPIO | Without it |
|---|---|---|---|
| MAX98357A (I2S) | BCLK / LRC / DIN | 26 / 27 / 25 | no sound; undetectable, the bus is one-way |
| SD card (SPI) | SCK / MISO / MOSI / CS | 18 / 21 / 19 / 5 | only the jingle and beeps play; reported in the log |
| PN532 (I2C) | SDA / SCL / RESET | 17 / 16 / 4 | no tags; reported in the log |
| Buttons (to GND) | PREV / PLAY / NEXT | 32 / 33 / 14 | everything goes through the console or the portal |
| WS2812B strip | DIN | 13 | no visual feedback |
| Battery sense | divider on B+ | 35 | gauge at zero, batt reports no reading |
Detailed wiring and Perma-Proto layout:
docs/materiel.md. Source of the plan:
hardware/wiring.html.
Only the ESP32 is required to boot: each missing module drops its feature without blocking start-up.
cd firmware
pio run -t upload # flash over USB
pio device monitor # serial console, 115200SD card: one folder per album at the root, filled with .mp3 files. Binding a
tag from the console:
tags list the bindings
bind <uid> /MyAlbum a folder on the card
bind <uid> builtin:boot the embedded jingle
Without a console: holding PLAY for 2 s at start-up opens the WroomTale
WiFi access point (password wroomtale), which stops after 5 min.
Full commands and settings: docs/console.md.
Short press: pause/resume, next track, previous track. Long press: volume +/-, stop on PLAY.
pio run -d firmware -t upload # the box
pio run -d firmware -e wroomtale-volume -t upload # buttons set on the volume
pio run -d firmware -e bt -t upload # A2DP spike| Topic | Decision | Reason |
|---|---|---|
| Audio lib | earlephilhower/ESP8266Audio |
ESP32-audioI2S no longer supports the ESP32 without PSRAM; ESP8266Audio decodes in ~30 KB of heap |
| Decoder | Helix in IRAM | gapless playback without PSRAM |
| WiFi | on only in config mode | the WiFi tasks preempt the decoder; the radio draws ~3× the idle current |
| OTA | none | 4 MB leaves no room for two app partitions |
| Web UI | PROGMEM | no SPIFFS partition, 3.75 MB left to the application |
| Cores | audio on 1, RFID/buttons on 0 | PN532 polling (50 ms timeout) would starve the decoder |
| LEDs | RMT peripheral | WS2812B at 800 kHz, no interrupt tolerated |
In French.