Iot-protocolsHow-ToBeginner · 4 min read

How to Use ADS1115 ADC with Raspberry Pi: Simple Guide

To use the ADS1115 ADC with a Raspberry Pi, connect it via I2C pins and use a Python library like Adafruit_ADS1x15 to read analog inputs. Initialize the ADC in your code, then read values from the desired channel using simple function calls.

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Syntax

Here is the basic syntax to read analog values from the ADS1115 using Python on Raspberry Pi:

import board, busio: Import I2C communication modules.
from adafruit_ads1x15.ads1115 import ADS1115: Import the ADS1115 class.
ads = ADS1115(i2c): Create an ADS1115 object using the I2C bus.
chan = AnalogIn(ads, ADS1115.P0): Select the analog input channel (e.g., P0).
value = chan.value: Read the raw ADC value.
voltage = chan.voltage: Read the voltage converted from the raw value.

python

import board
import busio
from adafruit_ads1x15.ads1115 import ADS1115
from adafruit_ads1x15.analog_in import AnalogIn

# Initialize I2C bus
i2c = busio.I2C(board.SCL, board.SDA)

# Create ADS1115 instance
ads = ADS1115(i2c)

# Create single-ended input on channel 0
chan = AnalogIn(ads, ADS1115.P0)

# Read raw value and voltage
raw_value = chan.value
voltage = chan.voltage

print(f"Raw ADC Value: {raw_value}")
print(f"Voltage: {voltage:.3f} V")

Output

Raw ADC Value: 12345 Voltage: 1.234 V

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Example

This example shows how to continuously read and print the voltage from channel 0 of the ADS1115 every second.

python

import time
import board
import busio
from adafruit_ads1x15.ads1115 import ADS1115
from adafruit_ads1x15.analog_in import AnalogIn

# Setup I2C and ADS1115

i2c = busio.I2C(board.SCL, board.SDA)
ads = ADS1115(i2c)
chan = AnalogIn(ads, ADS1115.P0)

while True:
    print(f"Voltage on channel 0: {chan.voltage:.3f} V")
    time.sleep(1)

Output

Voltage on channel 0: 1.234 V Voltage on channel 0: 1.230 V Voltage on channel 0: 1.235 V ...

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Common Pitfalls

Incorrect wiring: Make sure SDA and SCL pins on the Raspberry Pi connect to the ADS1115 SDA and SCL pins.
I2C not enabled: Enable I2C interface on Raspberry Pi using raspi-config.
Wrong I2C address: ADS1115 default address is 0x48; check with i2cdetect -y 1.
Missing libraries: Install adafruit-circuitpython-ads1x15 via pip.
Using wrong channel constants: Use ADS1115.P0 to ADS1115.P3 for single-ended inputs.

python

import board
import busio
from adafruit_ads1x15.ads1115 import ADS1115
from adafruit_ads1x15.analog_in import AnalogIn

# Wrong: Using wrong channel constant
# chan = AnalogIn(ads, 0)  # This will cause error

# Right:
i2c = busio.I2C(board.SCL, board.SDA)
ads = ADS1115(i2c)
chan = AnalogIn(ads, ADS1115.P0)  # Correct channel usage

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Quick Reference

Step	Description
Connect ADS1115 SDA to Raspberry Pi SDA (GPIO 2)	I2C data line connection
Connect ADS1115 SCL to Raspberry Pi SCL (GPIO 3)	I2C clock line connection
Enable I2C on Raspberry Pi	Use sudo raspi-config > Interface Options > I2C
Install Python library	pip3 install adafruit-circuitpython-ads1x15
Write Python code	Import libraries, create ADS1115 object, read channels
Run script	Get voltage readings from analog sensors

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Key Takeaways

Connect ADS1115 to Raspberry Pi using I2C pins SDA and SCL correctly.

Enable I2C interface on Raspberry Pi before running code.

Use the Adafruit ADS1x15 Python library for easy ADC reading.

Read analog values by creating an AnalogIn object for the desired channel.

Check wiring and I2C address if readings are incorrect or errors occur.