Professional Studio & Camera COB Light: Precision Optics, Dedicated BLE & Fail-Safe OTA
Modern cinema and content-creation workflows demand compact, high-output lighting with high color rendering (CRI > 96, TLCI > 97) and zero rolling-shutter flicker across wide camera frame rates. This project encompassed the ground-up schematic design, PCB layout, low-noise power electronics, and embedded firmware architecture for an on-camera/rig-mounted continuous COB light controlled locally or via a low-latency smartphone Bluetooth Low Energy (BLE) link.
Hardware & Dual-MCU System Architecture
- Optical Engine & Driver Topology: Implemented an ultra-efficient synchronous buck constant-current converter delivering sustained power to dual-channel (Warm White / Daylight) COB emitters. Running high-frequency (>32 kHz) PWM completely eliminates camera banding, optical strobing, and rolling-shutter artifacts at high frame rates and shutter angles.
- Master Controller (STM32 Cortex-M0+): Executes hardware-critical tasks, including high-resolution constant-current modulation, true-logarithmic perceived dimming (0.1%–100%), calibrated 2700K–6500K CCT blending, multi-point NTC temperature monitoring with dynamic thermal foldback, and local rotary encoder debouncing.
- Wireless Co-Processor (ESP32 - Pure BLE): Configured exclusively as a lightweight, low-power BLE peripheral (omitting Wi-Fi overhead to preserve power and RF bandwidth). Manages custom GATT services for instant parameter sync, scene presets, battery status telemetry, and over-the-air firmware updates.
- Host-to-Controller Bridge: A validated bidirectional UART/SPI interface with packet framing and CRC16 verification links the ESP32 and STM32, enabling coordinated operational changes and mediated firmware payload transfers.
Dedicated BLE Stack & Wireless Firmware Over-The-Air (FOTA)
- Mobile App Integration: Exposed low-latency GATT characteristics for real-time slider tracking of color temperature (Kelvin), brightness (0.1% resolution), and camera FX strobe modes.
- Dual-Bank BLE OTA Architecture: Implemented a robust chunk-based BLE OTA pipeline on the ESP32 featuring dual-bank flash partitioning (A/B slots) and SHA-256 integrity checks. The system ensures fail-safe execution, automatically rolling back to the active partition if transmission breaks or power drops mid-flash.
- Secondary Target Flashing: Supports remote firmware updates for the primary STM32 via bootloader handoff over the inter-processor UART bridge, ensuring complete system upgradability entirely through a smartphone.
Testing & Optical Validation
- Spectroradiometer Testing: Calibrated color-mixing matrices to deliver consistent CRI ≥ 96 and TLCI ≥ 98 across the entire 2700K to 6500K spectrum without green/magenta shift.
- High-Speed Camera Shutter Verification: Tested across high-speed capture profiles (up to 1000 FPS) to confirm zero light pulsation or CMOS rolling-shutter banding across all brightness levels.
- Thermal Soak & Stress Testing: Validated sustained thermal equilibrium under full-output continuous runs using forced heat-pipe heatsinking and active firmware current throttling.