How to Use Adafruit ADS1115 16Bit I2C ADC: Examples, Pinouts, and Specs

The Adafruit ADS1115 is a high-precision, 16-bit Analog-to-Digital Converter (ADC) that operates on an I2C bus interface. It is designed to accurately convert analog signals to digital form, allowing microcontrollers and other digital systems to process real-world data such as temperature, pressure, or light intensity. The ADS1115 is particularly useful in applications requiring high-resolution measurements, such as data loggers, sensors, and precision instrumentation.

• Resolution: 16-bit
• Sampling Rate: Up to 860 samples per second (SPS)
• Input Channels: 4 single-ended or 2 differential
• Programmable Gain Amplifier (PGA): Up to ±6.144V
• Supply Voltage: 2.0V to 5.5V
• Interface: I2C
• I2C Addresses: 0x48 (default), 0x49, 0x4A, 0x4B (selectable with address pin)

1. Power Connections: Connect VDD to a 2.0V to 5.5V power supply and GND to the system ground.
2. I2C Connections: Connect SCL and SDA to the corresponding I2C clock and data lines on your microcontroller. Use pull-up resistors as required by your I2C bus specifications.
3. Address Selection: Connect the ADDR pin to GND, VDD, SDA, or SCL to select one of the four possible I2C addresses.
4. Analog Inputs: Connect your analog signal to any of the A0 to A3 pins. For differential measurements, use pairs A0/A1 or A2/A3.

To use the ADS1115 with an Arduino, you can utilize the Adafruit ADS1X15 library. Here's a basic example of how to read a single-ended voltage from channel A0:

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

Adafruit_ADS1115 ads;  // Create an instance of the ADS1115

void setup() {
  Serial.begin(9600);
  ads.begin();  // Initialize the ADS1115
}

void loop() {
  int16_t adc0;  // Variable to hold the ADC result

  adc0 = ads.readADC_SingleEnded(0);  // Read from channel 0
  Serial.print("AIN0: "); Serial.println(adc0);
  delay(1000);  // Wait for a second
}

• Ensure that the input voltage does not exceed the selected full-scale range of the PGA.
• Use decoupling capacitors close to the power pins to minimize noise.
• Keep analog signal paths as short as possible to reduce noise pickup.
• Avoid running analog signal lines parallel to high-current traces to prevent interference.

• No response from the device: Check the I2C connections, ensure pull-up resistors are installed, and verify that the correct I2C address is being used.
• Inaccurate readings: Ensure that the input voltage is within the range set by the PGA. Check for noise in the analog signal and power supply lines.

Q: Can the ADS1115 be used with a 3.3V system? A: Yes, the ADS1115 can operate at voltages as low as 2.0V.

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 voltage that can be measured by the ADS1115? A: The maximum voltage is determined by the PGA setting, which can be up to ±6.144V.

Q: How can I use the ALERT pin? A: The ALERT pin can be configured for various functions such as a conversion ready signal or a threshold alert. Refer to the ADS1115 datasheet for detailed configuration options.

For further assistance, consult the ADS1115 datasheet and the Adafruit ADS1X15 library documentation.