xblink/docs/STATUS.md

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)

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

Group A — LP5562 Only

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

M1: LED Smoke Test

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

M2: Engine Patterns

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

M3: Hardcoded Pattern Library (COMPLETE)

• Define 5 const patterns in firmware (breathe, heartbeat, slow_pulse, rgb_cycle, color_wash)
• Implement pattern selector (cycle through patterns, 15s each)
• Reduce LED current to 2mA/ch (EH-realistic budget)
• 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)

• Write Ntag5Link<I2C> driver (src/ntag5/mod.rs)
• Implement session register access (CONFIG_0, CONFIG_1, EH_CONFIG)
• Implement EEPROM block read/write with write-verify
• Config check: read session regs, compare against expected, write NDEF result
• NDEF Type 5 text record writer for config check output
• 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)

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

M6: SRAM Mailbox (COMPLETE)

• Design SRAM mailbox protocol (docs/plans/2026-03-05-sram-mailbox-protocol.md)
• Add NTAG5 write_register, SRAM read/write, FD pin configuration
• Implement command protocol types and CRC helpers (src/ntag5/sram.rs)
• Implement all 7 command handlers (WRITE_PATTERN, GET_STATUS, SET_ACTIVE, SYNC_START/END, READ_LIBRARY/NEXT)
• Streaming transfer: single NFC hold for full library sync (one pattern per SRAM round-trip)
• FD pin polling in main idle loop (200ms interval, A1/PA04)
• 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

• Design GPIO-direct PWM architecture (docs/plans/2026-03-06-gpio-led-pivot.md)
• Implement software pattern engine with waveform LUTs (src/pattern/mod.rs)
• Implement XBLK v2 EEPROM format (16-byte entries, playlist support)
• Implement TCC PWM driver for 6 LED channels (src/led/pwm.rs)
• Implement TC4 50Hz animation timer ISR
• Implement power governor (proportional brightness scaling)
• Update main.rs for GPIO-direct boot flow
• Update SRAM mailbox protocol for v2 format (src/ntag5/sram.rs)
• Update Python serializer (tools/xblk_serialize.py)
• 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

• Configure SAMD21 EIC for FD pin wake
• Implement IDLE sleep during animation (TC4 ISR drives LEDs)
• 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

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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