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Richard b3deb0036f Initial commit — car parking distance sensor

ESP32-C3 Zero + VL53L1X ToF sensor + 3x LEDs with WiFi AP web calibration UI,
rolling average smoothing, auto-sleep, and NVS persistence.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

2026-04-06 12:31:15 +02:00

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CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

Car parking distance sensor using an ESP32-C3 Zero, VL53L1X Time-of-Flight laser sensor, and 3x 10mm LEDs (green/yellow/red). Wall-mounted in a garage, it measures distance to an approaching car and displays proximity via LED states. Includes a WiFi AP with web UI for remote calibration.

Build & Flash Commands

pio run — compile firmware
pio run -t upload — flash to ESP32-C3 (port: /dev/ttyACM0)
pio device monitor — serial monitor (115200 baud)
pio run -t upload && pio device monitor — flash and monitor in one shot

Note: close the serial monitor before flashing, or the port will be busy.

Architecture

Single-file firmware (src/main.cpp) using Arduino framework on PlatformIO. Three subsystems:

Sensor — VL53L1X on I2C (GPIO 5 SDA, GPIO 6 SCL), continuous mode at 50ms intervals
LEDs — 3x 10mm through-hole on GPIO 2 (green), GPIO 3 (yellow), GPIO 4 (red), active HIGH with 220Ω resistors
WiFi/Web — ESP32 runs as AP (SSID: ParkingSensor, pass: carpark1). Web server on 192.168.4.1 provides:
- Live distance readout (polls /api/status at 300ms)
- One-tap calibration (POST /api/calibrate) — sets current distance as the stop point
- Manual stop distance input (POST /api/set?stop=N)

LED Behaviour

LEDs off when distance > stop + 1000mm (ZONE_GREEN + 200mm headroom). Within range, zones are calculated as offsets above the calibrated stop distance:

Zone	Distance	LEDs
Far	> stop + 800mm	Green
Approaching	stop + 400 – stop + 800mm	Green + Yellow
Close	stop + 100 – stop + 400mm	Yellow + Red
Very close	stop – stop + 100mm	Red solid
STOP	< stop	Red flashing

Signal Processing

Rolling average: 5-sample moving average of valid readings smooths jitter
Bad reading filter: readings with range_status != 0 are discarded (status 7 = wrap-around is common at range edges)
Zero filter: distance 0 (no target) is discarded
Auto-sleep: LEDs turn off after 30s of stable distance (30mm tolerance), wake on movement

Calibration & Persistence

The stop distance is stored in NVS (ESP32 flash) via the Preferences library. It survives power cycles. Zone offsets are #define constants (ZONE_RED 100, ZONE_YELLOW 400, ZONE_GREEN 800) at the top of src/main.cpp. Stable tolerance (STABLE_TOLERANCE 30mm) and sleep timeout (SLEEP_TIMEOUT 30000ms) are also tuneable.

Hardware

Board: ESP32-C3 Zero (board target: esp32-c3-devkitm-1)
Sensor: VL53L1X ToF (I2C, Pololu library pololu/VL53L1X@^1.3.1)
LEDs: 10mm through-hole (green, yellow, red) with 220Ω resistors
Power: USB-C
Build flags: -DARDUINO_USB_MODE=1 -DARDUINO_USB_CDC_ON_BOOT=1 (required for serial over USB on C3 Zero)

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