Project Info
Author: Chris
Difficulty: Medium
Time Invested: 3 Hours

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           Most microcontrollers have an analog to digital converter hardware module included inside the chip, but CPLDs and FPGAs almost never do. While future CPLDs and FPGAs might be changed to add premade hardware modules, since the current ones do not it's a wise idea to learn how we can use an external analog to digital converter to get a digital equivalent of an analog value.
           In this article, we'll use the CPLD Dev Board that I assembled together years ago and add an analog to digital converter IC, along with an LED bar and some current limiting resistors for output to verify the A/D converter is working. VHDL is listed as a pre-req as we'll be using it to design our custom A/D interface.

FPGA/CPLD ADC Interface - Demonstration

FPGA/CPLD ADC Interface - Setup

Purpose & Overview of this project
           The purpose of this project is to build a system that can use a generic analog to digital converter IC to convert an analog voltage value to a digital value and then display that digital value on an LED bar. This will require a custom interface to the A/D converter IC and to the LED bar.
           An Altera EPM7128 CPLD will be used and since it's already on the CPLD Dev Board it's ready to go, a MAX150 8-bit analog to digital converter IC will be used for converting analog voltages to digital values and a standard 10 green LED bar will be used with some current limiting resistors to display the converted A/D value in both a binary and straight magnitudal way.