MCP4725 Hookup Guide Datasheet by SparkFun Electronics

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MCP4725 Digital to Analog Converter Hookup

Guide

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CONTRIBUTORS: JOELEB

To DAC, or Not to DAC...

When learning about the world of microcontrollers, you will come across

analog-to-digital converters quite frequently. These allows us to read in

signals from analog sensors and convert them into a digital language our

microcontrollers and other computational devices can understand.

However, what if you need to do the opposite? What if you need your

Arduino to speak the language of analog signals? Enter the MCP4725

Digital-toAnalog Converter Breakout.

This tiny IC allows you to do just that. By using the Arduino’s I C lines, you

can create a wide variety of analog waveforms on the other end.

Covered in This Tutorial

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In this tutorial, we will overview the breakout and discuss additional

hardware details. Then an assembly section will discuss how to connect

this breakout to a microcontroller. Last, the firmware will be broken down to

help you understand how the digital to analog conversion happens.

Suggested Reading

• Analog vs Digital

• Logic Levels

• Pull-up Resistors

• Analog to Digital Conversion (ADC)

•IC

• How to Use an Oscilloscope

Board Overview

Before we discuss hooking up the breakout, let’s go over some of the

features of this board.

Pinout

The first thing to point out is the pinout on this breakout now conforms to

the standard I C pinout we’ve started using on most devices that use the

two-wire interface. Thus, it is easy to solder some headers on the breakout

and plug it directly into an Arduino with the same pinout for the I C pins.

There is also the signal out and a GND pin grouped together to connect to

an oscilloscope or whatever other device you’re hooking up to the breakout.

Power

The breakout can be powered anywhere between 2.7V to 5.5V, making it

great for both 5V and 3.3V microcontrollers.

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Page 3 of 9 ' E (LUT. 12c -* PULLupsmio .

I C Communication

A few features have been added to this breakout to give the user more

flexibility with the IC, particularly when it comes to adding multiple DACs to

one bus. First, we’ve broken out the address selection pin (A0) to a jumper

pad. By default, this pin is pulled LOW to GND. To change the address of

your other device, simply de-solder the jumper and add a blob of solder to

the middle pad and the Vcc pad.

If you’re going to have more than one MCP4725 on a bus, you’ll also want

to disable the pull-up resistors on all but one breakout. To make this

easier, we’ve added another jumper on the back of the board. The pull-ups

are enabled by default. If you need to disable them, you’ll need to cut the

traces on the jumper pad with an Xacto knife. If you ever need to re-enable

the pull-ups, simply solder the three pads back together.

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Last, there are two mounting holes to mount this board inside the enclosure

of your choice.

Hooking it Up

To use the MCP4725, all you’ll need is some male headers, a SparkFun

RedBoard or other microcontroller, and a means to see your signal. Using

an oscilloscope will be the easiest way to get started.

First, solder the headers onto your breakout. We recommend using a 4-pin

header facing downward for the power and communication connections and

using a 2-pin header facing up for the Out and GND pins. See the below

image for an example.

Most Arduino boards have the I C on the A4 and A5 pins. Then, in the

firmware we’ll uplaod in the next section, we can set pins A2 and A3 as

GND and Vcc respectively to power the breakout. If you prefer to wire

everything to a breadboard, you can solder a 6-pin header and connect

everything with some jumper wires.

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Last, it’s time to connect the MCP4725 to whatever device you’ll be sending

analog signals. In this tutorial, we’ll be visualizing the signal with an

oscilloscope. Using the o-scope probes, you could connect to the headers

directly, or you could use some jumper wires. Make sure to not mix up the

Out and GND pins.

Firmware

With everything hooked up, it’s time to upload some code to the Arduino

that will allow the breakout to send analog signals. In this example, the

code will generate a simple sine wave.

Open up the Arduino IDE, and copy in this snippet of code:

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/*************************************************************

*****************

MCP4725ExampleWaveformSketch

JoelBartlett

SparkFunElectronics

Sept.11,2014

https://github.com/sparkfun/MCP4725_Breakout

Thissketchtakesdatafromalookuptabletoprovide

waveformstobegeneratedbytheMCP4725DAC.

Developmentenvironmentspecifics:

Arduino1.0+

HardwareVersionV14

Thiscodeisbeerware;ifyouseeme(oranyotherSparkFunem

ployee)atthelocal,

andyou'vefoundourcodehelpful,pleasebuyusaround!

Distributedasis;nowarrantyisgiven.

ThiscodebuildsoffthesketchwrittenbyMarkVandeWetterin

g,whichcanbefoundhere:

http://brainwagon.org/2011/02/24/arduinomcp4725breakoutboar

d/

#include<Wire.h>//IncludetheWirelibrarytotalkI2C

//ThisistheI2CAddressoftheMCP4725,bydefault(A0pulle

dtoGND).

//PleasenotethatthisbreakoutisfortheMCP4725A0.

#defineMCP4725_ADDR0x60

//FordeviceswithA0pulledHIGH,use0x61

//SinewaveTablesweregeneratedusingthiscalculator:

//http://www.daycounter.com/Calculators/SineGeneratorCalcula

tor.phtml

int lookup= 0;//varaiblefornavigatingthroughthetables

int sintab2[512]=

{

2048,2073,2098,2123,2148,2174,2199,2224,

2249,2274,2299,2324,2349,2373,2398,2423,

2448,2472,2497,2521,2546,2570,2594,2618,

2643,2667,2690,2714,2738,2762,2785,2808,

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2832,2855,2878,2901,2924,2946,2969,2991,

3013,3036,3057,3079,3101,3122,3144,3165,

3186,3207,3227,3248,3268,3288,3308,3328,

3347,3367,3386,3405,3423,3442,3460,3478,

3496,3514,3531,3548,3565,3582,3599,3615,

3631,3647,3663,3678,3693,3708,3722,3737,

3751,3765,3778,3792,3805,3817,3830,3842,

3854,3866,3877,3888,3899,3910,3920,3930,

3940,3950,3959,3968,3976,3985,3993,4000,

4008,4015,4022,4028,4035,4041,4046,4052,

4057,4061,4066,4070,4074,4077,4081,4084,

4086,4088,4090,4092,4094,4095,4095,4095,

4095,4095,4095,4095,4094,4092,4090,4088,

4086,4084,4081,4077,4074,4070,4066,4061,

4057,4052,4046,4041,4035,4028,4022,4015,

4008,4000,3993,3985,3976,3968,3959,3950,

3940,3930,3920,3910,3899,3888,3877,3866,

3854,3842,3830,3817,3805,3792,3778,3765,

3751,3737,3722,3708,3693,3678,3663,3647,

3631,3615,3599,3582,3565,3548,3531,3514,

3496,3478,3460,3442,3423,3405,3386,3367,

3347,3328,3308,3288,3268,3248,3227,3207,

3186,3165,3144,3122,3101,3079,3057,3036,

3013,2991,2969,2946,2924,2901,2878,2855,

2832,2808,2785,2762,2738,2714,2690,2667,

2643,2618,2594,2570,2546,2521,2497,2472,

2448,2423,2398,2373,2349,2324,2299,2274,

2249,2224,2199,2174,2148,2123,2098,2073,

2048,2023,1998,1973,1948,1922,1897,1872,

1847,1822,1797,1772,1747,1723,1698,1673,

1648,1624,1599,1575,1550,1526,1502,1478,

1453,1429,1406,1382,1358,1334,1311,1288,

1264,1241,1218,1195,1172,1150,1127,1105,

1083,1060,1039,1017,995,974,952,931,

910,889,869,848,828,808,788,768,

749,729,710,691,673,654,636,618,

600,582,565,548,531,514,497,481,

465,449,433,418,403,388,374,359,

345,331,318,304,291,279,266,254,

242,230,219,208,197,186,176,166,

156,146,137,128,120,111,103,96,

88,81,74,68,61,55,50,44,

39,35,30,26,22,19,15,12,

10,8,6,4,2,1,1,0,

0,0,1,1,2,4,6,8,

10,12,15,19,22,26,30,35,

39,44,50,55,61,68,74,81,

88,96,103,111,120,128,137,146,

156,166,176,186,197,208,219,230,

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242,254,266,279,291,304,318,331,

345,359,374,388,403,418,433,449,

465,481,497,514,531,548,565,582,

600,618,636,654,673,691,710,729,

749,768,788,808,828,848,869,889,

910,931,952,974,995,1017,1039,1060,

1083,1105,1127,1150,1172,1195,1218,1241,

1264,1288,1311,1334,1358,1382,1406,1429,

1453,1478,1502,1526,1550,1575,1599,1624,

1648,1673,1698,1723,1747,1772,1797,1822,

1847,1872,1897,1922,1948,1973,1998,2023

};

void setup()

{

Wire.begin();

//SetA2andA3asOutputstomakethemourGNDandVcc,

//whichwillpowertheMCP4725

pinMode(A2,OUTPUT);

pinMode(A3,OUTPUT);

digitalWrite(A2,LOW);//SetA2asGND

digitalWrite(A3,HIGH);//SetA3asVcc

}

//

void loop()

{

Wire.beginTransmission(MCP4725_ADDR);

Wire.write(64);//cmdtoupdatetheDAC

Wire.write(sintab2[lookup]>> 4);//the8mostsigni

ficantbits...

Wire.write((sintab2[lookup]& 15)<< 4);//the4leastsign

ificantbits...

Wire.endTransmission();

lookup= (lookup+1)&511;

}

Once the sketch is uploaded, fire up the o-scope, connect the probe, if you

haven’t yet, and you should be greeted with a nice looking sine wave.

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Resources and Going Further

With that, you should be able to get your MCP4725 working the way you’d

like and integrated into your next project. For more information on the

MCP4725, please visit the links below.

• MCP4725 on Brainwagon

• Sine Lookup Table Generator

• MCP4725 Datasheet

Need more? Check out these other SparkFun tutorials:

• Pulse-width Modulation

• Sound Detector Hookup Guide

• AD8232 Heart Rate Monitor Hookup Guide

• Hacking MindWave Mobile

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MCP4725 Hookup Guide Datasheet by SparkFun Electronics

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