How to Use ADS1115 16-Bit ADC - 4 Channel : Examples, Pinouts, and Specs

The ADS1115, manufactured by Adafruit (part #1085), is a high-precision, low-power, 16-bit analog-to-digital converter (ADC) with four multiplexed channels. It is designed for applications requiring precise voltage measurement, such as sensor interfacing, data acquisition systems, and portable instrumentation. With its I2C-compatible interface, the ADS1115 is easily integrated into a wide range of microcontroller-based systems, including those built with Arduino platforms.

• Resolution: 16-bit
• Sampling Rate: 8 samples per second (SPS) to 860 SPS
• Input Voltage Range: ±256 mV to ±6.144 V (selectable gain)
• Interface: I2C
• Operating Voltage: 2.0 V to 5.5 V
• Channels: 4 single-ended or 2 differential inputs
• Programmable Comparator

1. Connecting the ADS1115 to Arduino:

   • Connect VDD to 5V (or 3.3V if system requires).
   • Connect GND to Arduino GND.
   • Connect SCL to Arduino A5 (or the SCL pin if using a different Arduino model).
   • Connect SDA to Arduino A4 (or the SDA pin if using a different Arduino model).
   • ADDR can be connected to GND, VDD, SDA, or SCL to set the I2C address.

2. Arduino Library and Initialization:

   • Install the Adafruit ADS1X15 library via the Arduino Library Manager.
   • Include the library in your sketch and create an instance of the ADS1115.

#include <Wire.h>
#include <Adafruit_ADS1015.h>

Adafruit_ADS1115 ads(0x48); // Use default I2C address 0x48

void setup() {
  Serial.begin(9600);
  ads.begin();
}

void loop() {
  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);
}

3. Best Practices:
   • Ensure that the input voltage does not exceed the selected voltage range.
   • Use bypass capacitors close to the power pins to minimize noise.
   • Keep analog signal paths as short as possible to reduce interference.

• No response from the device: Check the wiring, ensure that the I2C address is correct, and that the Arduino is supplying power to the ADS1115.
• Inaccurate readings: Verify the input voltage range and the gain settings. Ensure that the ADS1115 is properly grounded.

Q: Can the ADS1115 be used with both 5V and 3.3V systems? A: Yes, the ADS1115 can operate with a supply voltage from 2.0 V to 5.5 V.

Q: How do I change the I2C address of the ADS1115? A: The I2C address can be changed by connecting the ADDR pin to GND, VDD, SDA, or SCL.

Q: What is the maximum sampling rate of the ADS1115? A: The ADS1115 can sample up to 860 samples per second.

Q: Can the ADS1115 measure negative voltages? A: The ADS1115 can measure negative voltages in differential mode, but not in single-ended mode.

For further assistance, consult the Adafruit ADS1115 datasheet and the Adafruit support forums.