Knowledge Base

Connecting the ADC Differential Pi to a Pico

Downloading and Installing the library

To download to your Raspberry Pi, type in the terminal:

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

To install the MicroPython Library, use the Thonny Python IDE from https://thonny.org/

Create a file for your chosen board and copy the contents of the Python file into that board's directory. For example, for the ADC Differential Pi, create a new file in thonny called ADCDifferentialPi.py and copy contents from ADCDifferentialPi.py into the new file and save it onto the Raspberry Pi Pico board.

Create a second file where your main program will reside and import the board library at the top of the program.

from ADCDifferentialPi import ADCDifferentialPi

Run with "Run Current Command" or F5 in Thonny.

Classes:

ADCDifferentialPi(address, address2, rate, sda, scl)

Parameters:
address: I2C address for channels 1 to 4; defaults to 0x68
address2: I2C address for channels 5 to 8; defaults to 0x69
rate: bit rate, values can be 12, 14, 16 or 18. Defaults to 18
sda (optional): I2C SDA pin. If no value is set, the class will use pin 20.
scl (optional): I2C SCL pin. If no value is set, the class will use pin 21.

Functions:

read_voltage(channel) 

Read the voltage from the selected channel
Parameters: channel - 1 to 8 Returns: number as a float between -2.048 and +2.048

read_raw(channel) 

Read the raw int value from the selected channel
Parameters: channel - 1 to 8 Returns: number as an int

set_pga(gain)

Set the gain of the PGA on the chip
Parameters: gain - 1, 2, 4, 8
Returns: null

set_bit_rate(rate)

Set the sample bit rate of the ADC
Parameters: rate - 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_conversion_mode(mode)

Set the conversion mode for the ADC
Parameters: mode - 0 = One-shot conversion, 1 = Continuous conversion
Returns: null

Usage

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

from ADCDifferentialPi import ADCDifferentialPi

Next, you must initialise the ADC object:

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 board.

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

You can now read the voltage from channel 1 with the following:

x = adc.read_voltage(1)