CDS-55 Photoresistor Module for STM32 (C)

A lightweight C module for reading analog light levels from the CDS-55 (KLS6-3537) photoresistor using STM32 HAL drivers. Designed for polling-mode ADC use, with optional scaled output for control applications like PID loops, logging, or UI display.

Features

• Supports 12-bit ADC (or higher)
• Optional scaled output (0–100%)
• Tracks both raw and scaled values
• Simple initialization and usage
• Based on CDS-55 photoresistor characteristics

Target Sensor

• Model: CDS-55 (a.k.a. KLS6-3537)
• Light resistance: 18–50 kΩ @ 10 lux
• Dark resistance: ≥2 MΩ
• Spectral peak: 540 nm
• Response time: ~30 ms

Usage

photoCell_t sensor;
photoCell_init(&sensor, true, 200, 3900);  // scaled = true, map raw ADC [200–3900] to 0–100
 
uint8_t light = readSensor(&sensor);
printf("Light: %d (raw: %d)\n", sensor.current_level, sensor.last_raw_value);
````
 
## File Layout

include/ PhotoCell.h src/ PhotoCell.c examples/ main.c // Example integration with HAL ADC

## License
 
MIT