# xblink Project Status

**Current Milestone**: GPIO-Direct LED Pivot (replacing LP5562)
**Last Updated**: 2026-03-07

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## Phase 0 — Project Setup (COMPLETE)

- [x] Initialize git repository and Rust project
- [x] Configure build target (thumbv6m-none-eabi)
- [x] Create project documentation (README, CLAUDE.md, STATUS, DEVELOPMENT_PLAN)
- [x] Verify `cargo build --release` compiles
- [x] Initial git commit

## Group A — LP5562 Only

**Hardware needed**: XIAO M0 + LP5562EVM + mini-USB cable

### M1: LED Smoke Test

- [x] Copy LP5562 driver from `../ntag5-samd21-lp562/src/lp5562.rs`
- [x] Create `src/led/mod.rs` with re-exports
- [x] Update `main.rs` with I2C init + GPIO EN + LP5562 direct PWM test
- [x] Verify `cargo build --release` compiles
- [x] Verify LP5562 I2C control via EVM USB-to-I2C bridge (`tools/lp5562_evm.py`)
- [x] Flash XIAO M0 and verify RGBW LED channels with Rust firmware

### M2: Engine Patterns

- [x] Build breathing pattern (1 engine, ramp up/down, branch loop)
- [x] Build heartbeat pattern (1 engine, fast ramp, slow decay)
- [x] Build RGB cycle (3 engines, trigger-synced phase offset)
- [x] Verify LP5562 runs patterns autonomously (MCU idle loop)
- [x] Verify MCU can stop and switch patterns (8s cycle between all 3)

### M3: Hardcoded Pattern Library (COMPLETE)

- [x] Define 5 const patterns in firmware (breathe, heartbeat, slow_pulse, rgb_cycle, color_wash)
- [x] Implement pattern selector (cycle through patterns, 15s each)
- [x] Reduce LED current to 2mA/ch (EH-realistic budget)
- [x] Document engine program structures (`docs/lp5562-engine-reference.md`)

## Group B — Add NTAG5Link

**Hardware needed**: + NTAG5Link Click board + I2C jumper

### M4: NTAG5 EEPROM Read/Write (COMPLETE)

- [x] Write `Ntag5Link<I2C>` driver (`src/ntag5/mod.rs`)
- [x] Implement session register access (CONFIG_0, CONFIG_1, EH_CONFIG)
- [x] Implement EEPROM block read/write with write-verify
- [x] Config check: read session regs, compare against expected, write NDEF result
- [x] NDEF Type 5 text record writer for config check output
- [x] Verified on hardware: config check passes, NDEF readable via NFC
- [ ] Register map module (`src/ntag5/registers.rs`) — deferred, constants in mod.rs for now

### M5: Boot-from-EEPROM (COMPLETE)

- [x] Design XBLK binary pattern format (`docs/plans/2026-03-05-eeprom-pattern-format.md`)
- [x] Implement XBLK deserializer (`src/pattern/mod.rs`: parse_header, parse_pattern_entry)
- [x] Implement XBLK serializer (`src/pattern/mod.rs`: serialize_pattern_entry, serialize_header, crc16)
- [x] Update main.rs: boot → read EEPROM → parse → program LP5562 → idle, with fallback
- [x] MCU self-provisioning: write hardcoded patterns to EEPROM on first boot
- [x] Write Python serializer tool (`tools/xblk_serialize.py`) for PCSC pattern uploads
- [x] Verified on hardware: self-provisioning writes XBLK, subsequent boots load from EEPROM

### M6: SRAM Mailbox (COMPLETE)

- [x] Design SRAM mailbox protocol (`docs/plans/2026-03-05-sram-mailbox-protocol.md`)
- [x] Add NTAG5 `write_register`, SRAM read/write, FD pin configuration
- [x] Implement command protocol types and CRC helpers (`src/ntag5/sram.rs`)
- [x] Implement all 7 command handlers (WRITE_PATTERN, GET_STATUS, SET_ACTIVE, SYNC_START/END, READ_LIBRARY/NEXT)
- [x] Streaming transfer: single NFC hold for full library sync (one pattern per SRAM round-trip)
- [x] FD pin polling in main idle loop (200ms interval, A1/PA04)
- [x] I2C bus swapping for LP5562 reprogramming after pattern updates
- [ ] Hardware test: flash and verify with PCSC reader / phone app (pending FD pin wiring)

## GPIO-Direct LED Pivot (2026-03-07)

LP5562 requires VDD >= 2.7V, incompatible with 1.8V NFC energy harvesting.
Replaced with SAMD21E GPIO-direct PWM driving 6 red LEDs.
See `docs/plans/2026-03-06-gpio-led-pivot.md` for full design.

### LED Pivot Implementation

- [x] Design GPIO-direct PWM architecture (`docs/plans/2026-03-06-gpio-led-pivot.md`)
- [x] Implement software pattern engine with waveform LUTs (`src/pattern/mod.rs`)
- [x] Implement XBLK v2 EEPROM format (16-byte entries, playlist support)
- [x] Implement TCC PWM driver for 6 LED channels (`src/led/pwm.rs`)
- [x] Implement TC4 50Hz animation timer ISR
- [x] Implement power governor (proportional brightness scaling)
- [x] Update main.rs for GPIO-direct boot flow
- [x] Update SRAM mailbox protocol for v2 format (`src/ntag5/sram.rs`)
- [x] Update Python serializer (`tools/xblk_serialize.py`)
- [x] Verify `cargo build --release` compiles
- [ ] Hardware test: wire LEDs to A1/A2/D2/D3, flash and verify animations
- [ ] Measure power consumption with multimeter

## Group C — Power + Recovery

**Hardware needed**: + Hall sensor + multimeter

### M7: Sleep/Wake

- [x] Configure SAMD21 EIC for FD pin wake
- [x] Implement IDLE sleep during animation (TC4 ISR drives LEDs)
- [x] Implement STANDBY sleep when no pattern active
- [ ] Measure current: IDLE (animating) vs STANDBY vs total system

### M8: Recovery Mode

- [ ] Wire hall sensor to EIC-capable GPIO
- [ ] Implement boot-time hall sensor check
- [ ] Recovery: load default pattern, skip EEPROM, stay awake
- [ ] Test with magnet

### M9: Power Characterization

- [ ] Measure current at various LED brightness / resistor values
- [ ] Test NTAG5Link EH output with phone NFC at 1.8V
- [ ] Tune power governor budget for optimal brightness
- [ ] Document real power numbers

## Group D — Future

### Custom PCB (SAMD21E)

- [ ] Port to `atsamd-hal` with `samd21e` feature
- [ ] Add LEDs 2-5 on PA06/PA07 (freed from I2C conflict on custom PCB)
- [ ] Custom `memory.x` linker script
- [ ] PCB design and fabrication

### Companion App (React Native)

- [ ] NFC communication + pattern editor + upload

### Firmware Update (NFC OTA)

- [ ] Custom bootloader if needed post-implant

---

## Open Questions

| Question | Status | Notes |
|----------|--------|-------|
| Energy harvesting power budget | TBD | Multimeter measurements at 1.8V |
| Optimal LED resistor value | TBD | 10-47 ohm, affects brightness vs power |
| Power governor budget default | Set to 50 | Configurable via companion app |
| Firmware update strategy | Deferred | UF2 for dev, NFC OTA evaluated later |
| Hall sensor part selection | Decided | DRV5032FB (SOT-23, 8.4mT, prototype) |

## Hardware Inventory

| Item | Status | Notes |
|------|--------|-------|
| Seeed XIAO M0 | Available | Dev board MCU (SAMD21G18A) |
| LP5562EVM | Available (unused) | Removed from design (VDD > 2.7V) |
| NTAG5 Link Click | Available, partially wired | Missing I2C jumper to XIAO |
| Low-Vf red LEDs | Need to source | Kingbright APTD1608 or similar, Vf ~1.7V |
| Resistors (10-47 ohm) | Need to source | Current limiting for GPIO-direct LEDs |
| Hall effect sensor | Not available | Need to source — TI DRV5032FB (SOT-23) |
| ACR1552 PCSC reader | Available | For ntag5sensor Python tooling |
| Multimeter | Available | For power budget measurements |