How to use ADS1115 ADC module with Arduino

As we know that Arduino contains ADC channels of 10-bit resolution. But if we require the measurement to be done with higher resolution then we can opt for the ADS1115 module. It contains 16 bit ADC with 4 channels and communicates with I2C protocol.  Out of 16 bits, 15 bits are used for the measurement and the 16^th bit is for the polarity. So we can measure the negative values from this also.

Setting the gain

In this, we can set various resolution as per level of our input signal. we just have to use below code to st the resolution. 

Gain select command                            Gain                 Voltage Range             Resolution

                                                                                                                 ADS1015         ADS1115

   ads.setGain(GAIN_TWOTHIRDS);      //  2/3x gain +/- 6.144V     1 bit = 3mV        0.1875mV

   ads.setGain(GAIN_ONE);                     // 1x gain   +/- 4.096V       1 bit = 2mV        0.125mV

   ads.setGain(GAIN_TWO);                    // 2x gain   +/- 2.048V       1 bit = 1mV        0.0625mV

   ads.setGain(GAIN_FOUR);                   // 4x gain   +/- 1.024V      1 bit = 0.5mV      0.03125mV

   ads.setGain(GAIN_EIGHT);                  // 8x gain   +/- 0.512V      1 bit = 0.25mV    0.015625mV

   ads.setGain(GAIN_SIXTEEN);             // 16x gain  +/- 0.256V     1 bit = 0.125mV  0.0078125mV

The default gai is the 2/3x gain.

Image

The module looks like the below image. 

The code is very simple and uses the Adafruit ADS1115 library which can be downloaded from this link- https://github.com/adafruit/Adafruit_ADS1X15 

 

Connections

The connections are very simple and are made through the pins available on board.

 

 

But to get the data we just need to connect the below connections

Vdd:- To the device supply

GND:- Device ground

SCL:- SCL pin of Arduino

SDA:- SDA pin of Arduino

ADDR:- This pin defines the address for the device for I2C communication. And if we are using only one chip then just connect this to ground. Different addresses for different connections are shown below as

 

 A0 to A3:- To analog input lines 

Circuit Connections

The sample connections are shown below.

 

 

Example Code

Below is the example code

 

#include <Wire.h>

#include <Adafruit_ADS1015.h>

 // Adafruit_ADS1115 ads;  /* Use this for the 16-bit version */

Adafruit_ADS1015 ads;     /* Use thi for the 12-bit version */

 void setup(void)

{

  Serial.begin(9600);

  Serial.println("Hello!");

  Serial.println("Getting single-ended readings from AIN0..3");

  Serial.println("ADC Range: +/- 6.144V (1 bit = 3mV/ADS1015, 0.1875mV/ADS1115)");

  // The ADC input range (or gain) can be changed via the following

  // functions, but be careful never to exceed VDD +0.3V max, or to

  // exceed the upper and lower limits if you adjust the input range!

  // Setting these values incorrectly may destroy your ADC!

  //                                                                ADS1015  ADS1115

  //                                                                -------  -------

  // ads.setGain(GAIN_TWOTHIRDS);  // 2/3x gain +/- 6.144V  1 bit = 3mV      0.1875mV (default)

  // ads.setGain(GAIN_ONE);        // 1x gain   +/- 4.096V  1 bit = 2mV      0.125mV

  // ads.setGain(GAIN_TWO);        // 2x gain   +/- 2.048V  1 bit = 1mV      0.0625mV

  // ads.setGain(GAIN_FOUR);       // 4x gain   +/- 1.024V  1 bit = 0.5mV    0.03125mV

  // ads.setGain(GAIN_EIGHT);      // 8x gain   +/- 0.512V  1 bit = 0.25mV   0.015625mV

  // ads.setGain(GAIN_SIXTEEN);    // 16x gain  +/- 0.256V  1 bit = 0.125mV  0.0078125mV

   ads.begin();

}

 void loop(void)

{

  int16_t adc0, adc1, adc2, adc3; 

  adc0 = ads.readADC_SingleEnded(0);

  adc1 = ads.readADC_SingleEnded(1);

  adc2 = ads.readADC_SingleEnded(2);

  adc3 = ads.readADC_SingleEnded(3);

  Serial.print("AIN0: "); Serial.println(adc0);

  Serial.print("AIN1: "); Serial.println(adc1);

  Serial.print("AIN2: "); Serial.println(adc2);

  Serial.print("AIN3: "); Serial.println(adc3);

  Serial.println(" ");

  delay(1000);

}

 The datasheet for this can be downloaded from this link

http://www.ti.com/lit/gpn/ads1115

Try the module and comment your observations below. 

Aniruddh Sharma

Ani-Lab