OXRecorder Firmware

Developer documentation & API reference

This is the central reference for every class in the OXRecorder namespace. Each class has an API reference page (what every method and parameter does, with copy-paste examples) and a How It Works page (the design and internals). Use the sidebar — or the search box in it — to navigate.

Want to reuse this code in your own project? The SDK & download page shows how to download the managers as a ready-to-use PlatformIO SDK and wire it up.

Hardware blueprint

The OXRecorder hardware is an ESP32-S3 Super Mini with three peripherals: an INMP441 microphone (I2S), a microSD adapter (SPI), and a WS2812 status LED, powered by a 3.7 V LiPo battery through a TP4056, plus a battery-sense divider on GPIO3 and a reset button on GPIO5. The full pin map is below — anyone with this page can build the board. Each peripheral's detailed wiring is on its How It Works page (mic, SD, LED, battery sense).

Battery 3.7 V LiPo + − TP4056 charge + boost 3.7 V → 5 V out 5V GND 5 V rail Battery sense GPIO3 ADC raw cell VCC 1k 1k midpoint ESP32-S3 Super Mini 5V GND GPIO3 ADC GPIO9 GPIO8 GPIO7 3V3 out GPIO10 GPIO11 GPIO13 GPIO12 GPIO4 GPIO5 INMP441 I2S mic SCK WS SD VDD 3V3 L/R → GND microSD SPI adapter CS SCK MISO MOSI VCC 3V3 GND 10uF WS2812 status LED DIN 5V 330 Ω 3V3→5V Reset button hold 10 s → reset GPIO5 GND
data clock / resistors power (5V / 3V3) ground

OXRecorder hardware blueprint — power: Battery → TP4056 (5 V) → ESP32-S3, microSD & INMP441 on the ESP32's 3V3 output; GPIO3 senses the raw battery VCC/GND terminals through a 1k/1k divider, not the TP4056 output rail; 10uF across microSD VCC/GND; 330 Ω and a level shifter on the WS2812 data line if the LED runs at 5 V.

PeripheralPeripheral pinESP32-S3 Super MiniManaged by
INMP441 mic (I2S)SCKGPIO9OXAudioManager
WSGPIO8
SDGPIO7
L/RGND
microSD (SPI)CSGPIO10OXFileManager
SCKGPIO11
MISOGPIO13
MOSIGPIO12
VCC3V3 with 10uF to GND at adapter
GNDGND
Battery sense dividertop resistor 1kraw battery VCC / cell +, before TP4056 outputOXBatteryManager
midpointGPIO3 (ADC)
bottom resistor 1kraw battery GND / cell −
WS2812 LEDDINGPIO4 via 330 Ω; level shift if LED VDD is 5 VOXLEDManager
Reset buttonterminal AGPIO5 (strapping pin)OXConfigManager — hold 10 s to reset
terminal BGND

Signal pins are the firmware defaults and can be overridden in each manager's begin(). Internal flash storage (LittleFS) needs no wiring.

Power topology

The 3.7 V LiPo feeds a TP4056 module, which charges the cell and boosts its output to 5 V. That 5 V rail powers the ESP32-S3 Super Mini (5V pin). The INMP441 and a 3.3 V-compatible microSD adapter run from the ESP32-S3's regulated 3V3 output, not the 5 V rail.

FromToRailNotes
Battery 3.7 V (+/−)TP4056 B+ / B−3.7 VCharge + protect the cell.
TP4056 OUT 5 VESP32-S3 Super Mini 5V5 VBoosted output powers the MCU board.
ESP32-S3 3V3 outmicroSD VCC3.3 VUse an adapter with 3.3 V MISO; place 10uF from VCC to GND near the adapter.
TP4056 OUT 5 VWS2812 5V5 VUse a 3.3 V-to-5 V level shifter between GPIO4 and DIN.
Battery cell + / −GPIO3 through 1k/1k dividerADC senseTop resistor goes to raw battery VCC; bottom resistor goes to raw battery GND. Do not connect this divider to TP4056 OUT 5 V.
ESP32-S3 3V3 outINMP441 VDD3.3 VMic runs on the MCU's regulated 3.3 V only.
Common GNDall devices—TP4056, MCU, mic, SD, and LED share ground.

The ESP32-S3 GPIOs are not 5 V tolerant. Keep the SD bus at 3.3 V, and add a 3.3 V-to-5 V level shifter after the 330 Ω series resistor when the WS2812 runs at 5 V. The SD adapter should have a local 10uF capacitor from VCC to GND to absorb card current spikes. The INMP441 is kept on 3.3 V because it is a 1.8–3.6 V part.

Classes