# FreeInk SDK

> FreeInk is an MIT-licensed, hardware-independent C++ SDK for ESP32-class e-paper readers. It hides e-paper controllers, waveforms and board wiring behind injectable interfaces, so one firmware can drive many panels. Libraries are self-contained PlatformIO dependencies you add à la carte; a single binary can carry several boards and pick one at runtime.

Hardware-independent C++ firmware SDK for e-paper readers. Source: [github.com/Free-Ink/freeink-sdk](https://github.com/Free-Ink/freeink-sdk). The full text of every page below is also available as one file: [https://freeink.org/llms-full.txt](https://freeink.org/llms-full.txt).

## Getting started

- [Overview](https://freeink.org/docs/overview): What FreeInk is, why it exists, and how the pieces fit together.
- [Quickstart](https://freeink.org/docs/quickstart): Drive an e-paper panel with FreeInk in a few minutes.
- [Sticky reader starter](https://freeink.org/docs/sticky): Build a minimal EPUB reader: All Books list, paged reader, and edge gestures.
- [PlatformIO setup](https://freeink.org/docs/installation): Add the FreeInk libraries to a PlatformIO project.

## Concepts

- [Architecture](https://freeink.org/docs/architecture): The facade, panel drivers, the bus, and board config.
- [Build composition](https://freeink.org/docs/build-composition): Compose a binary along two axes: devices × capabilities.
- [Supported devices](https://freeink.org/docs/devices): The device matrix, refresh behavior and touch support.

## Libraries

- [Libraries overview](https://freeink.org/docs/api): Reference for the FreeInk libraries: APIs, defaults and build flags.
- [EInkDisplay](https://freeink.org/docs/lib-display): The display facade: framebuffer, geometry, refresh and grayscale.
- [InputManager](https://freeink.org/docs/lib-input): Buttons and capacitive touch behind one object.
- [BatteryMonitor](https://freeink.org/docs/lib-battery): ADC, BQ27220 I²C fuel gauge, or M5PM1 PMIC — one API.
- [SDCardManager](https://freeink.org/docs/lib-sd): SdFat-over-SPI or native 4-bit SDMMC, one API.
- [FrontlightManager](https://freeink.org/docs/lib-frontlight): PWM frontlight with warm/cool control.
- [AudioManager](https://freeink.org/docs/lib-audio): WAV playback through an I2S codec (Murphy M3 ES8388, M5 PaperColor ES8311).
- [LedManager](https://freeink.org/docs/lib-led): Addressable RGB LEDs: color, brightness and non-blocking flashes.
- [Buzzer](https://freeink.org/docs/lib-buzzer): LEDC PWM square-wave tones on a passive buzzer.
- [Microphone](https://freeink.org/docs/lib-mic): PDM microphone capture to 16-bit PCM.
- [Rtc](https://freeink.org/docs/lib-rtc): PCF8563 / DS3231 real-time clock over I²C.
- [EnvironmentSensor](https://freeink.org/docs/lib-env): SHT40 temperature + humidity over I²C.
- [Imu](https://freeink.org/docs/lib-imu): LSM6DS3TR-C 6-axis accelerometer + gyroscope.
- [PowerManager](https://freeink.org/docs/lib-power): Portable deep-sleep wake-on-power-button.
- [MemoryManager](https://freeink.org/docs/lib-memory): On-demand RAM reclaim via priority-ordered cache sinks.
- [RecoveryBoot](https://freeink.org/docs/lib-recovery): Boot-time OTA recovery escape hatch (button combo).
- [SecureNet](https://freeink.org/docs/networking): Opt-in wolfSSL TLS 1.3 transport.
- [BleKeyboardHost](https://freeink.org/docs/lib-ble): BLE HID host for keyboards, page turners and remotes.
- [BoardConfig](https://freeink.org/docs/lib-board): Board profiles and the runtime-active device.
- [XteinkDetect](https://freeink.org/docs/lib-detect): Runtime X3/X4 and display-controller detection via bus fingerprinting.
- [FreeInkUI](https://freeink.org/docs/lib-ui): Optional immediate-mode UI framework for e-paper.
- [Component gallery](https://freeink.org/docs/lib-ui-components): Prebuilt FreeInkUI components, previewed from the real 1-bit renders.
- [Icons](https://freeink.org/docs/lib-icons): freeink::Icon format, vendored Lucide set, and a generator.
- [FreeInkBook](https://freeink.org/docs/lib-book): A complete EPUB reading engine: layout, cache, fonts, international text.

## Guides

- [Adding a device](https://freeink.org/docs/adding-a-device): Bring up a new board: profile, driver config, build env.
- [MCU portability](https://freeink.org/docs/mcu-portability): Keep a consumer building across ESP32-C3 and ESP32-S3.

## Reference

- [Repository layout](https://freeink.org/docs/repository-layout): Where each library lives in the SDK tree.