pic micro kypad to analouge converts.

[mj21]

hi guys,

i am trying to build a programmable power supply for my lab, now i have made the CC/CV circuit and the regulator bit of it. now instead of using POTS or rotary encoders or even buttons to move the voltage or current up and down i was thinking of using a key pad to just input the voltage i want.

i have a rough idea what it might need but i a bit lost in how to do it.  the circuit for CC/CV is based on op-amps and a voltage reference, same kinda design of Daves power supply. but instead of LT3080 i am using LM317. varying the reference voltage to the non-inverting of the op-amps creates a voltage at the other end of the circuit which in turn changes the voltage on the ADJ pin of an LM317 with a pass transistor for current gain.

so in theory if my key pad had kind of a digital to analogue converter with the reference voltage being the same as my reference from the CC/CV circuit is can out put a voltage straight to the non-inverting input of the op-amp and change the voltage accordingly.

can some one please let me know how i go about doing something like this?