4. Velleman experiment boards K8055 and K8055N upgrade projects

PIC18F2xJ50 family has in fact 16 A/D input sources connected to the A/D converter via multiplexer. PIC18F2xJ50 supports up to 10 external analog inputs. Whereas, internal inputs 14 and 15 are used to measure two important internal power supply voltages: Vddcore and Vref. Vddcore is microcontroller core voltage that is around 2.5 V. The refference voltage is always 1.2 V and it is mainly used for calibration. If you read this channel, you should always get a value close to 372. The internal voltage levels may also be used to check the current operating conditions of the microcontroller, if power source is unreliable or unstable.

K8055 and K8055N boards offer many ways for modifications. It is not a necessity to use USB address selection jumpers. You may remove them and use RA2 input as third A/D input under condition that you add appropriate electronics (at least the voltage level adaptor, if you deal with the voltage range outside 0 ..  3.3 V).

There are also other possibilities for modifications.

Archive of Velleman originally programmed microcontrollers... You probably won't need them anymore...