PCB & Firmware Sensor Refresh

My current board is built around an STM32F429VIT6 and two legacy light-measuring devices that have just gone end-of-life. I have sourced drop-in phototransistors with the same pinout and essentially the... (Budget: $25 - $50 USD, Jobs: Altium Designer, C Programming, Electrical Engineering, Electronics, Embedded Systems, Microcontroller, PCB Layout, Software Development, Software Engineering, STM32)