This Python Library is for use with ADC Differential Pi Raspberry Pi expansion board from
https://www.abelectronics.co.uk

The ADC Differential Pi is an 18-bit, 8-channel, I2C ADC board that can be used to read analogue voltages from sensors and other devices. It uses the Microchip MCP3424 Delta-Sigma ADC chip and can be used with any Raspberry Pi model that has a 40-pin GPIO connector, along with other compatible small board computers.

The library provides functions to read the voltage from the ADC channels, set the gain of the PGA, set the bit mode of the ADC and set the conversion mode of the ADC.

For more information on the ADC Differential Pi board, please visit the product page at https://www.abelectronics.co.uk/p/65/adc-differential-pi

For user guides and troubleshooting tips, please visit our knowledge base at https://www.abelectronics.co.uk/kb/article/1130/adc-differential-pi

The example python files can be found in /ABElectronics_Python_Libraries/ADCDifferentialPi/demos

1. Downloading and Installing the Library
   • Using Classes Without Installing the Library
2. Software Requirements
3. Classes
   • ADCDifferentialPi
4. Functions
   • read_voltage
   • read_raw
   • set_pga
   • set_bit_mode
   • set_conversion_mode
   • set_i2c_address1
   • set_i2c_address2
   • get_i2c_address1
   • get_i2c_address2
5. Quick Start

To install the library, you will need the Python3 build and install packages. To install them, run the following command.

sudo apt update
sudo apt install python3-build python3-installer git

Download the ABElectronics_Python_Libraries to your Raspberry Pi:

git clone https://github.com/abelectronicsuk/ABElectronics_Python_Libraries.git

To install the python library, navigate into the ABElectronics_Python_Libraries folder and run:

python3 -m build
sudo python3 -m installer dist/*.whl

The ADC Differential Pi library is located in the ADCDifferentialPi directory

To use a specific part of our Python library in your project without installing the entire library, you can copy the necessary class file into your project's directory. For example, to use the ADC Differential Pi, copy the ADCDifferentialPi.py file from the ADCDifferentialPi directory to where your project files are located. After doing this, you can use the class in your program by adding an import statement at the beginning of your Python code. This allows you to directly utilize the class's functionality in your project.

from ADCDifferentialPi import ADCDifferentialPi

The library requires I2C to be enabled on the Raspberry Pi and the smbus2 or python3-smbus Python library to be installed.

sudo pip3 install smbus2

To configure the I2C bus, follow our Enabling I2C on the Raspberry Pi tutorial.

ADCDifferentialPi(address, address2, mode, bus)

Parameters:
address: I2C address for channels 1 to 4, 0x68 to 0x6F. Defaults to 0x68
address2: I2C address for channels 5 to 8, 0x68 to 0x6F. Defaults to 0x69
mode: bit-mode, values can be 12, 14, 16 or 18. Defaults to 18-bit resolution.
bus (optional): I2C bus number (integer). If no value is set the class will try to find the i2c bus automatically using the device name.

read_voltage(channel) 

Parameters: channel - 1 to 8
Returns: number as a float between 0 and 5.0

Read the voltage from the selected channel.

read_raw(channel) 

Parameters: channel - 1 to 8
Returns: number as an int

Read the raw int value from the selected channel

set_pga(gain)

Parameters: gain - 1, 2, 4, 8
Returns: null

Set the gain of the PGA on the chip

set_bit_mode(mode)

Parameters: mode - 12, 14, 16, 18
Returns: null
12 = 12 bit (240SPS max)
14 = 14 bit (60SPS max)
16 = 16 bit (15SPS max)
18 = 18 bit (3.75SPS max)

Set the sample bit mode of the ADC. The ADC Differential Pi can be set to 12, 14, 16 or 18 bits. The default is 18 bits. Higher bit modes provide more accurate readings, but they also require more processing time and can take longer to get a reading. Lower bit modes provide less accurate readings, but they are faster.

set_conversion_mode(mode)

Parameters: mode - 0 = One-shot conversion, 1 = Continuous conversion
Returns: null

Set the conversion mode for the ADC. The ADC Differential Pi can be set to one-shot or continuous conversion mode.

One shot mode is useful for applications where you only need to take a single reading at a time, such as when measuring the voltage of a battery. Continuous mode is useful for applications where you need to take multiple readings in quick succession, such as when measuring the temperature of a sensor. One shot mode has lower power consumption than in continuous mode, but it may take longer to get a reading. Continuous mode has a higher power consumption, but it can provide faster readings.

set_i2c_address1(address)

Parameters: address - 0x68 to 0x6F
Returns: null

Set the I2C address for the ADC on channels 1 to 4

set_i2c_address2(address)

Parameters: address - 0x68 to 0x6F
Returns: null

Set the I2C address for the ADC on channels 5 to 8

get_i2c_address1()

Returns: I2C address

Gets the I2C address for the ADC on channels 1 to 4

get_i2c_address2()

Returns: I2C address

Gets the I2C address for the ADC on channels 5 to 8

If you're familiar with Python and Raspberry Pi, here's how to get up and running quickly:

To use the ADC Differential Pi library in your code, you must first import the ADCDifferentialPi class from the ADCDifferentialPi library:

from ADCDifferentialPi import ADCDifferentialPi

Create an instance of the ADCDifferentialPi class by specifying the I2C addresses and bit mode:

adc = ADCDifferentialPi(0x68, 0x69, 18)

The first two arguments are the I2C addresses of the ADC chips. The values shown are the default addresses of the ADC Differential Pi board.

The third argument is the bit mode you want to use on the ADC chips. The sample mode can be 12, 14, 16 or 18 bits. The default is 18 bits.

Use the read_voltage method to read the voltage from a specific channel:

adc.read_voltage(1)

Replace 1 with the desired channel number (1 to 8).