Lux sensor

Lux Sensor

USB ambient light sensor based on a CH552G MCU and VEML7700 ALS, with:

• KiCad hardware design in the repo root
• minimal CH552 firmware that exposes readings over USB CDC ACM
• optional Linux host daemon that maps lux readings to panel brightness

Repository Layout

• lux-sensor.kicad_sch, lux-sensor.kicad_pcb, lux-sensor.kicad_pro: hardware source
• firmware/: CH552 firmware and build rules
• host/: Linux daemon and service example
• BOM.csv, BOM_PCBWay.csv, BOM_NOTES.md: purchasing and assembly notes
• *.pretty/, *.kicad_mod, *.kicad_sym: local footprint and symbol assets
• CH552DS1.pdf, VEML7700.pdf: datasheet references used during design
• SCHEMATIC_REVIEW.md: electrical review notes and known design considerations
• POWER_PASSIVES_REVIEW.md: CH543D USB-A 5 V power passive recommendations

Generated fabrication exports and firmware build artifacts are intentionally ignored by Git.

Hardware

Core parts:

• CH552G
• VEML7700-TR
• USB-A plug
• local decoupling capacitors and I2C pull-ups

The board is intended to enumerate as a USB serial device and stream lines such as:

raw=2468 lux=123.40

Firmware

Build requirements:

• sdcc
• make
• packihx
• objcopy

Build:

make -C firmware

Upload with the factory bootloader tooling:

make -C firmware upload

Host Daemon

The Linux-side daemon reads the CDC ACM stream and writes brightness through the kernel backlight interface.

Dry run:

python3 host/luxd.py --dry-run --verbose

Run against the real backlight node:

sudo python3 host/luxd.py

See firmware/README.md and host/README.md for the full firmware and daemon details.