Knowledge Base

The ADC-DAC Pi Zero can be used with the Raspberry Pi Pico available at www.raspberrypi.com/products/raspberry-pi-pico/

We have a MicroPython library to use with the Raspberry Pi Pico at GitHub at github.com/abelectronicsuk/ABElectronics_MicroPython_Libraries

The example Python files can be found in /ABElectronics_MicroPython_Libraries/ADCDACPi/demos/

Connecting the ADC-DAC Pi Zero to the Raspberry Pi Pico

The ADC-DAC Pi Zero library uses the following pins on the Raspberry Pi Pico board.

Pico Pin	Pico GPIO	Function	Pi Pin	Pi GPIO
4	GP2	SPI SCK	23	GPIO 11
5	GP3	SPI0 TX	19	GPIO 10
6	GP4	SPI0 RX	21	GPIO 9
7	GP5	ADC SPI CE0	24	ADC SPI CE0
25	GP19	DAC SPI CE1	26	GPIO 7
40	VBUS	5V	2	5V Power
38	GND	GND	6	Ground
36	3V3(OUT)	3V3	1	3v3 Power

To use a different pin, you can edit the ADCDACPi.py on lines 24 to 36.

---

Wiring Diagram:

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-DAC Pi, create a new file in thonny called ADCDACPi.py, copy contents from ADCDACPi.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 program's top.

from ADCDACPi import ADCDACPi

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

---

Functions:

Initialising the ADCDACPi object.

adcdac = ADCDACPi(gain_factor)

Parameter: gain_factor - 1 or 2 When the gain is set to 1, the voltage range of the DAC will be 0 to 2.048V. When the gain is set to 2, the voltage will be 0 to 3.3V

---

read_adc_voltage(channel, mode) 

Read the voltage from the selected channel on the ADC
Parameter: channel - 1 or 2
Parameter: mode - 0 = single-ended, 1 = differential
Returns: number as a float between 0 and 2.048

---

read_adc_raw(channel, mode) 

Read the raw value from the selected channel on the ADC
Parameter: channel - 1 or 2
Parameter: mode - 0 = single-ended, 1 = differential
Returns: int

---

set_adc_refvoltage(voltage)

Set the reference voltage for the analogue to digital converter.
The ADC uses the raspberry pi 3.3V power as a voltage reference, so using this method to set the reference to match the exact output voltage from the 3.3V regulator will increase the accuracy of the ADC readings.
Parameters: voltage
Returns: null

---

set_dac_voltage(channel, voltage)

Set the voltage for the selected channel on the DAC. The DAC has two gain values, 1 or 2, which can be set when the ADCDAC object is created. A gain of 1 will give a voltage between 0 and 2.047 volts. A gain of 2 will provide a voltage between 0 and 3.3 volts.
Parameters: channel - 1 or 2, voltage - target DAC voltage
Returns: null

---

set_dac_raw(channel, value)

Set the raw value for the selected channel on the DAC
Parameters: channel - 1 or 2, value int between 0 and 4095
Returns: null

Usage

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

from ADCDACPi import ADCDACPi

Next, you must initialise the adcdac object and set a gain of 1 or 2 for the DAC:

adcdac = ADCDACPi(1)

Set the reference voltage.

adcdac.set_adc_refvoltage(3.3)

Read the voltage from channel 2 and store it in a variable called x.

x = adcdac.read_adc_voltage(2)

---