Virtual AD
Julio Cesar Palacios Reyes


As you know the pic 16f628 doesn´t have AD so here you have a 
little solution. 

V_AD function is a virtual AD, it isnt so fast and only can
measure 71.8% of VDD.

	 If VDD=5V  then      3.6>V_AD>0.
 	 If VDD=5.5 then      3.9>V_AD>0

It has 4 chanel conected to PORTA (A0, A1, A2, A4).
it use the comparators and the Voltage Reference Module
To obtain the closer voltage.

The function return a value between 0 and 69 and  you have 
        
	69>V_AD>0
        voltage=(V_AD * VDD) /96

EJ.
	if the function return 40 and VDD=5  then 
	voltage=( 40  *  5 ) /96 =2.08 volts. 


If the voltage is higer than 3.6 (3.9 if vDD=5.5) the function
return 96. voltage=96*5/96, so  voltage=5. 

you need to be sure that PORTA is config like input.