# xblink Project Status

**Current Phase**: Phase 0 — Project Setup
**Last Updated**: 2026-03-03

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## Phase 0 — Project Setup

- [x] Initialize git repository
- [x] Initialize Rust project with `cargo init`
- [x] Configure `.cargo/config.toml` for thumbv6m-none-eabi
- [x] Set up `Cargo.toml` with XIAO M0 BSP and embedded-hal 1.0
- [x] Create `.gitignore`
- [x] Create initial `src/main.rs` (blink + LP5562 EN pin on D0/A0)
- [x] Create project directory structure (`src/led/`, `src/ntag5/`, `src/pattern/`, `docs/`)
- [x] Create README.md
- [x] Create CLAUDE.md
- [x] Create docs/STATUS.md (this file)
- [x] Create docs/DEVELOPMENT_PLAN.md
- [x] Verify `cargo build --release` compiles
- [x] Initial git commit

## Phase 1 — LP5562 Driver Integration

- [ ] Copy LP5562 driver from `../ntag5-samd21-lp562/src/lp5562.rs`
- [ ] Define `LedController` trait in `src/led/mod.rs`
- [ ] Wrap LP5562 driver to implement `LedController`
- [ ] Add GPIO EN pin control to LP5562 wrapper (D0/A0 hardware enable)
- [ ] Test LP5562 direct PWM on XIAO M0 + LP5562EVM
- [ ] Test LP5562 engine programs (breathing, color cycling)
- [ ] Implement `SimplePwm` driver as second `LedController` implementation

## Phase 2 — NTAG5Link Driver (MCU-side I2C Slave)

- [ ] Implement NTAG5Link register map (`src/ntag5/registers.rs`)
- [ ] Implement EEPROM block read/write via I2C (`src/ntag5/eeprom.rs`)
- [ ] Implement SRAM mailbox read/write (`src/ntag5/sram.rs`)
- [ ] Implement session register access
- [ ] Test EEPROM read/write with XIAO M0 + NTAG5Link Click board
- [ ] Test SRAM mailbox read/write
- [ ] Verify round-trip: write pattern via PCSC reader, read back on MCU

## Phase 3 — Pattern Storage Format

- [ ] Design binary pattern format (header + engine programs + LED mapping)
- [ ] Document format in `docs/PATTERN_FORMAT.md`
- [ ] Implement pattern deserializer (`src/pattern/mod.rs`)
- [ ] Implement LP5562 engine program builder from pattern data (`src/pattern/engine.rs`)
- [ ] Implement pattern serializer (for MCU-side EEPROM writes)
- [ ] Test: write pattern via PCSC, MCU reads and programs LP5562

## Phase 4 — Power Management

- [ ] Characterize energy harvesting power budget with oscilloscope
- [ ] Determine optimal EH voltage/current settings (target: 3.0V, 9.0mA+)
- [ ] Implement SAMD21E STANDBY sleep mode
- [ ] Configure EIC wake on NTAG5Link FD pin
- [ ] Configure EIC wake on hall sensor GPIO
- [ ] Test full boot → program → sleep → wake cycle
- [ ] Measure total system current draw in each state

## Phase 5 — NFC Communication Protocol

- [ ] Design SRAM mailbox protocol (command/response frames)
- [ ] Implement MCU-side protocol handler
- [ ] Implement chunked transfer for patterns > 252 bytes
- [ ] Extend ntag5sensor Python tooling with xblink protocol commands
- [ ] Test pattern upload via PCSC reader
- [ ] Test with VivoKey RawNFC app

## Phase 6 — Recovery and Safe Mode

- [ ] Implement hall sensor GPIO input with debounce
- [ ] Implement recovery mode detection at boot
- [ ] Recovery behavior: hardcoded default pattern, skip EEPROM, stay awake
- [ ] Set recovery flag in SRAM for phone app detection
- [ ] Test recovery mode end-to-end

## Phase 7 — Firmware Update Strategy

- [ ] Evaluate NFC pass-through bootloader feasibility (see DEVELOPMENT_PLAN.md)
- [ ] Evaluate UF2 + NFC hybrid approach
- [ ] Implement chosen update mechanism
- [ ] Test firmware update end-to-end
- [ ] Document update procedure

## Phase 8 — Custom PCB (SAMD21E)

- [ ] Port from `xiao_m0` BSP to bare `atsamd-hal` with `samd21e` feature
- [ ] Remap pin assignments for SAMD21E18A (32-pin QFN)
- [ ] Provide custom `memory.x` linker script
- [ ] Design PCB schematic (SAMD21E + NTAG5Link + LP5562 + hall sensor + antenna)
- [ ] PCB layout for implant form factor
- [ ] Fabricate and test prototype PCB

## Phase 9 — Companion App

- [ ] React Native project setup
- [ ] NFC communication layer (ISO15693 via platform APIs)
- [ ] Pattern editor UI
- [ ] Pattern upload via NFC
- [ ] Firmware version check / status display

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## Open Questions

| Question | Status | Notes |
|----------|--------|-------|
| Energy harvesting power budget | TBD | Need oscilloscope measurements with LP5562EVM + NTAG5 Click |
| Optimal LED current per channel | TBD | Must fit within EH budget, probably 2-5mA/ch |
| Firmware update strategy | Under evaluation | NFC pass-through vs UF2 hybrid, see DEVELOPMENT_PLAN.md |
| NTAG5Link I2C slave address | Assumed 0x54 | Verify with Click board when jumper available |
| SAMD21E18A package sourcing | Not started | Verify QFN-32 availability for custom PCB phase |
| Antenna design | Not started | Loop antenna for 13.56MHz, PCB-integrated or wire coil |

## Hardware Inventory

| Item | Status | Notes |
|------|--------|-------|
| Seeed XIAO M0 | Available | Dev board MCU (SAMD21G18A) |
| LP5562EVM | Available | TI eval module, RGBW LEDs, I2C addr 0x30 |
| NTAG5 Link Click | Available, partially wired | Missing I2C jumper to XIAO |
| Hall effect sensor | Not available | Need to source |
| ACR1552 PCSC reader | Available | For ntag5sensor Python tooling |