MCP4921E SPI 12bit DAC Module

Description

MCP4921E SPI 12bit DAC Module

This is a precision Digital-to-Analog Converter (DAC) module built around the Microchip MCP4921, a 12-bit DAC with SPI interface. Designed for easy integration with microcontrollers such as Arduino, ESP32, and STM32, this module allows you to generate analog voltages from digital values.

A unique feature of this module is the selectable voltage reference—you can choose between using the system VCC or a precise 4.096V reference generated by an onboard MCP1541 voltage reference IC. This flexibility allows you to maintain high output accuracy in various operating conditions.

Features:

• ✅ MCP4921 12-bit DAC (SPI interface, 1-channel)

• ✅ Selectable VREF:

  • VCC

  • 4.096V from MCP1541

• ✅ Compatible with 3.3V and 5V logic systems

• ✅ Onboard 10k pull-down resistor on output

• ✅ SPI Header: Easy connection to Arduino or other microcontrollers

• ✅ Output terminal block for easy analog signal wiring

• ✅ Decoupling capacitors included (10µF and 100nF) for clean VREF and power lines

🔌 Pinout (Header J3):

Typical Applications

• Learn how DACs work in microcontroller projects

• Generate analog voltage signals (waveform, audio, or control voltage)

• Sensor simulation and calibration

• Signal processing and test equipment DIY projects

PCB Specifications

• Material: FR4, 1.6 mm thickness

• Copper: 1 oz (35 µm)

• Solder mask: Blue (other colors on bulk order)

• Silkscreen: White with clear labeling

• Dimensions: Compact (~25×20 mm, adjust per your layout)

Testing & Usage:

Connect this module to your Arduino using the SPI pins and use standard MCP4921 Arduino libraries or custom SPI code to control output voltage (0–4095 steps). The output voltage will scale between 0V and the selected VREF.

Arduino Test Code for MCP4921 DAC

Connections (based on your schematic):

• MOSI → Arduino pin 11

• SCK → Arduino pin 13

• CS → Arduino pin 10

• VREF: Select with jumper: VCC or MCP1541 output.

#include <SPI.h>

#define DAC_CS 10 // Chip Select pin for MCP4921

void setup() {
Serial.begin(9600);
SPI.begin();

pinMode(DAC_CS, OUTPUT);
digitalWrite(DAC_CS, HIGH); // Idle state

Serial.println(“MCP4921 DAC Test Starting…”);
}

void loop() {
for (int val = 0; val < 4096; val += 256) {
writeDAC(val);
Serial.print(“DAC Output: “);
Serial.println(val);
delay(500);
}
}

void writeDAC(int value) {
// MCP4921: 12-bit value (0-4095), with control bits
uint16_t command = 0b0011000000000000; // Start bits: 0b0011 = A channel, buffered, gain=1x, active
command |= (value & 0x0FFF); // 12-bit DAC value

digitalWrite(DAC_CS, LOW);
SPI.beginTransaction(SPISettings(20000000, MSBFIRST, SPI_MODE0));
SPI.transfer16(command);
SPI.endTransaction();
digitalWrite(DAC_CS, HIGH);
}

How to Test:

1. Upload the code to your Arduino Uno.

2. Connect a multimeter to the VoutA pin of the MCP4921 (or screw terminal).

3. You should see the output voltage step up every 0.5 seconds.

   • If VREF = 4.096V, expect output from 0V to ~4.095V.

   • If VREF = VCC, expect output from 0V to ~VCC.