Building a serial voltage meter to measure from 0 to 5 volts DC is actually pretty easy. Using MeLabs PicBasic, and Microsoft’s Visual Basic Version 5 Pro. You need Visual Basic Pro version because you will have to use Basic’s MSComm control. This control is not available in the Visual Basic 5 “Learning” Edition. The PIC16C71 simplifies the task even more by having a built in A/D converter. Pins 17,18,1,2 are the analog inputs AIN0,AIN1,AIN2,AIN3 respectively.
Read More Source:
http://www.rentron.com/serial.htm
http://electronics-diy.com
Thank you