Uses simple MSP430F2013 uC with 16bit SD A/D converter for fast sampling.
Sensor can be any photo diode (e.g. BP 104 S) or the TCS3400x I2C Multi Channel Ambient Light Sensor. (Only one can be populated at a time).
Illumination LEDs and Sensors can be placed on both sides of the PCB.
Note: MSP430F2013 has no UART, so RXD/TXD must be emulated in Software.