# Project Documentation for CrossPoint Reader Firmware

**Date:** 2026-02-09

## Task

Create three documentation files in `/mod/docs/` covering the Xteink X4 hardware capabilities, project file structure, and CI/build/code style for the CrossPoint Reader firmware.

## Changes Made

### New Files

1. **`mod/docs/hardware.md`** -- Device hardware capabilities documentation covering CPU (ESP32-C3), 16MB flash with partition layout, 480x800 eink display (2-bit grayscale, 3 refresh modes), 7 physical buttons, SD card storage, battery monitoring, WiFi networking, USB-C, and power management (deep sleep with GPIO wakeup).

2. **`mod/docs/file-structure.md`** -- Complete project file structure map documenting `src/` (main app with Activity-based UI system), `lib/` (16 libraries including EPUB engine, HAL, fonts, XML/ZIP/JPEG support), `open-x4-sdk/` (hardware driver submodule), `scripts/` (build helpers), `test/` (hyphenation tests), `docs/` (upstream docs), and `.github/` (CI/templates).

3. **`mod/docs/ci-build-and-code-style.md`** -- CI pipeline documentation covering 4 GitHub Actions workflows (CI with format/cppcheck/build/gate jobs, release, RC, PR title check), PlatformIO build system with 3 environments, clang-format 21 rules (2-space indent, 120-col limit, K&R braces), cppcheck static analysis config, and contribution guidelines (semantic PR titles, AI disclosure, scope alignment).

## Follow-up Items

- None. All three documents are complete and ready for review.