Arduino MCP492X

The Microchip MCP4921 and MCP4922 are 12 bit digital to analog converters with an SPI interface. The MCP4921 has one DAC output, the MCP4922 has two.

This library is built around the Arduino default SPI library and uses the designated SPI pins, in addition to a configurable chip select pin, passed in the constructor.

Usage

Wiring

Look up the designated SPI pins for your Arduino board, and wire up as follows:

Where "your CS" is whichever pin you'd like to use as chip select on your arduino board.

You can google "(your arduino board) pinout" to find pin diagrams. Look for a diagram that includes the SCK/MOSI/MISO designators. For example, for the Arduino Pro Micro board, you'd search "Arduino pro micro pinout"

Installing the library

Method 1: ZIP file

1. Download this repository as a .ZIP file: Download Arduino-MCP492X
2. Open Arduino IDE
3. Click Sketch > Include Library > Add .ZIP library...
4. Select the library
5. Click Sketch > Include Library > Contributed Libraries > MCP492X

Note: This will install the library on your computer but will not include it within your project if you were to transfer the files to someone else. If you want it all-in-one, I recommend method 2.

Method 2: Include in your project folder

You can also save the .h and .cpp files directly in you arduino project's folder, and then reference it as follows:

#include "MCP492X.h"

You may want to consider making a directory for just libraries though, if you project consists of several files. If the directory inside your project directory called "libs", the include line changes to:

#include "libs/MCP492X.h"

Code

This is the bare minimum to get started with one of these DACs in an Arduino project:

#include <MCP492X.h> // Include the library

#define PIN_SPI_CHIP_SELECT_DAC 9 // Or any pin you'd like to use

MCP492X myDac(PIN_SPI_CHIP_SELECT_DAC);

void setup() {
  // put your setup code here, to run once:
  myDac.begin();
}

void loop() {
  // put your main code here, to run repeatedly:

  // Write any value from 0-4095
  myDac.analogWrite(2048);

  // If using an MCP4922, write a value to DAC B
  myDac.analogWrite(1, 3172);
}

Function descriptions

begin()

Initializes the library, by starting the SPI bus and configuring some settings.

It's required to call this in setup().

analogWrite(unsigned int value)

Writes a 12-bit value to the DAC output. If this is on an MCP4922, it uses channel A.

analogWrite(bool odd, unsigned int value)

Writes a 12-bit value to a specific DAC output. If this is on an MCP4921, the value passed for odd is ignored. Otherwise, 0 selects the "even" DAC (A), and 1 selects the "odd" DAC (B).

value remains the 12-bit value you want to write.

analogWrite(bool odd, bool buffered, bool gain, bool active, unsigned int value)

Provides full access to all the control bits you can send to the DAC. Consult the data sheet for more information on each of the control bits.