ADS1115 (ADC)

Microcontrollers like Arduino usually have a built-in A/D converter (ADC = analog-to-digital converter) with a resolution of 10 bits, meaning they can distinguish a maximum of 1024 values. The ADC module discussed below is based on the ADC IC ADS1115, an A/D converter with a resolution of 16 bits and 4 channels, which can be easily used with microcontrollers. Thanks to its resolution, it can distinguish up to 65,536 values.
Furthermore, it features an internal amplifier (PGA = Programmable Gain Amplifier), allowing it to measure very small voltages. It also includes an alarm function that can be used for voltage monitoring. This means the microcontroller can enter a power-saving mode during inactive periods while the ADS1115 continues to operate.

Features/Specifications

📄 ADS1115 datasheet (2035 kB)

Connections

Operating Modes

The ADS1115 can operate in 3 different modes, though only the following 2 modes can be directly selected:
Single-shot mode or Continuous conversion mode.
If single-shot mode is selected and no A/D conversion is currently taking place, the ADS1115 enters the third possible mode, the Power-down mode, until a new single-shot measurement is started.

Power-Saving Mode

If high power savings are required, the ADS1115 can be operated with the following settings:

• Operating mode: single-shot mode
• Data rate: 860 SPS (Samples Per Second)
• Number of measurements: low, e.g., 5 times per second

At a data rate of 860 SPS, the A/D conversion time is approximately ~1.2 ms. So if, for example, 5 measurements per second are sufficient, the chip remains in power-down mode for 994 ms, during which the current consumption, according to the datasheet, is only ~1.5 µA.

PGA (Programmable Gain Amplifier)

The gain of the Programmable Gain Amplifier (PGA) can be set to values of 2/3, 1, 2, 4, 8, or 16. The resulting measurement range FS (Full-Scale Range) and the voltage resolution are shown in the following table:

The voltages to be measured must always be positive; negative results are only possible in differential voltage measurements. The voltage present at an analog input must always be between 0V and VDD (±0.3V); otherwise, the ADC may be damaged.

Used Components

Setup & Programming

Read potentiometer continuously

Arduino Uno

The following code uses the library MyADS1115 by Retian.

#include "MyADS1115.h"

MyADS1115 ADS;

void setup() {
   Serial.begin(9600);
   if (!ADS.isReady()) {
      Serial.println("ADS1115 not ready!");
      while (true);
   }

   ADS.init();
   ADS.setMux(ADS1115_MUX_AIN0_GND); // Voltage A0 -> GND
   ADS.setGain(ADS1115_PGA_6P144); // Gain to 6,144 V (Full Scale)
   ADS.setRate(ADS1115_RATE_8); // Sample rate: 8 SPS
   ADS.setMode(ADS1115_MODE_CONTINUOUS); // Continuous reading
}

void loop() {
   static int value = 0;
   static float voltage = 0.0;

   value = ADS.readConversion();
   voltage = ADS.readVoltage();

   Serial.println("Value=" + String(value) + " (" + String(voltage) + " mV)");
   delay(200);
}

Further information

• ADC-Modul ADS1115 [german]
• ADS1115 – A/D-Wandler mit Verstärker [german]
• How To Use ADS1115 16-Bit ADC with ESP32