xblink/docs/STATUS.md

# xblink Project Status

**Current Milestone**: M6 — SRAM Mailbox
**Last Updated**: 2026-03-05

---

## 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

- [ ] Implement SRAM read/write (`src/ntag5/sram.rs`)
- [ ] Design command/response protocol
- [ ] Implement MCU-side protocol handler
- [ ] Test pattern update via NFC without power-cycling

## Group C — Power + Recovery

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

### M7: Sleep/Wake

- [ ] Configure SAMD21 EIC for FD pin wake
- [ ] Implement STANDBY sleep after LP5562 programming
- [ ] Verify LP5562 keeps running during MCU sleep
- [ ] Measure current: active 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 current settings
- [ ] Test NTAG5Link EH output with phone NFC
- [ ] Find optimal brightness vs EH budget balance
- [ ] Document real power numbers

## Group D — Abstraction + Polish

### M10: LedController Trait

- [ ] Define trait based on proven usage patterns from Groups A-C
- [ ] Implement for LP5562 wrapper
- [ ] Refactor main.rs to trait-based API

### M11: SimplePwm Driver

- [ ] Implement only if single-color LED hardware is available

## Group E — Future

### Custom PCB (SAMD21E)

- [ ] Port to `atsamd-hal` with `samd21e` feature
- [ ] 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 in M9 |
| Optimal LED current per channel | TBD | Probably 2-5mA/ch, verify in M9 |
| Firmware update strategy | Deferred | UF2 for dev, NFC OTA evaluated later |
| NTAG5Link I2C slave address | Assumed 0x54 | Verify in M4 with Click board |
| Pattern binary format | Deferred to M5 | Design after M2-M3 engine experience |
| Hall sensor + EN circuit | Designed | Wired-AND: hall + MCU open-drain on EN with 1M pull-up. See `docs/plans/2026-03-03-hall-en-design.md` |
| Hall sensor part selection | Decided | DRV5032FB (SOT-23, 8.4mT, prototype) → DRV5032FE (X2SON 1x1mm, final PCB) |
| EN pull-up value | Decided | 1M — zero steady-state draw, 3µA when EN low, ~10µs rise time |

## Hardware Inventory

| Item | Status | Notes |
|------|--------|-------|
| Seeed XIAO M0 | Available | Dev board MCU (SAMD21G18A) |
| LP5562EVM | Available | TI eval module, RGBW LEDs, I2C addr 0x30 |
| Mini-USB cable | Available | USB-C, used for flashing XIAO M0 |
| NTAG5 Link Click | Available, partially wired | Missing I2C jumper to XIAO |
| Hall effect sensor | Not available | Need to source — TI DRV5032FB (SOT-23) for prototype |
| ACR1552 PCSC reader | Available | For ntag5sensor Python tooling |
| Multimeter | Available | For power budget measurements |