Today I will present you our letter sensor. You will find a descripion in this pdf-file:
Following by the „Eagle“ based board:
sfh_4550 (Datasheet of the LED)
and by the source code:
and, at last, by the stl-file for the cover of the LEDs and the fototransistors:
I hope you will understand it. Of course it is possible to take another microcontroller, if you normally do not use PICs from Microchip(R). It needs to have 8 analogue input pins and 7 digital input/output pins. And, of course, it might have not the same pin design.