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Lesson 10: PCF8591 ADC DAC Converter Module

In this lesson, you’ll learn how to connect the Raspberry Pi Pico W with the PCF8591 ADC DAC Converter Module using MicroPython. You’ll establish an I2C connection, initialize the PCF8591 module, and read analog values from its channels. This hands-on session will deepen your grasp of analog-to-digital conversion and I2C communication on the Raspberry Pi Pico W. The module’s potentiometer is connected to AIN0 using jumper caps, and the D2 LED on the module is connected to AOUT, so you can see that the brightness of D2 LED changes as you rotate the potentiometer.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Universal Maker Sensor Kit	94	Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction	Purchase Link
Raspberry Pi Pico W	BUY
PCF8591 ADC DAC Converter Module	BUY
Breadboard	BUY

Wiring

../_images/Lesson_10_PCF8591_Module_bb.png

Code

Note

Open the 10_pcf8591_module.py file under the path of universal-maker-sensor-kit-main/pico/Lesson_10_PCF8591_Module or copy this code into Thonny, then click “Run Current Script” or simply press F5 to run it. For detailed tutorials, please refer to Open and Run Code Directly.
Here you need to use the PCF8591.py, please check if it has been uploaded to Pico W, for a detailed tutorial refer to Upload the Libraries to Pico.
Don’t forget to click on the “MicroPython (Raspberry Pi Pico)” interpreter in the bottom right corner.

from machine import I2C, Pin
import time
from PCF8591 import PCF8591

# Setup I2C connection on pins 20 (SDA) and 21 (SCL)
i2c = I2C(0, sda=Pin(20), scl=Pin(21))

# Initialize the PCF8591 module at address 0x48
pcf8591 = PCF8591(0x48, i2c)  # Adjust the address if needed

# Check if the PCF8591 module is connected
if pcf8591.begin():
    print("PCF8591 found")

# Main loop to read analog values
while True:
    # Read and print the analog value from channel AIN0
    AIN0 = pcf8591.analog_read(PCF8591.AIN0)
    print("AIN0 ", AIN0)  # PCF8591.CHANNEL_0 can also be used
    # Additional channels can be read by uncommenting the following lines
    # print("AIN1 ", pcf8591.analog_read(PCF8591.AIN1))
    # print("AIN2 ", pcf8591.analog_read(PCF8591.AIN2))
    # print("AIN3 ", pcf8591.analog_read(PCF8591.AIN3))

    # Write the value back to AOUT. This will change the brightness of the D2 LED on the module.
    pcf8591.analog_write(AIN0)

    # Wait for 0.2 seconds before the next read
    time.sleep(0.2)

Code Analysis

Importing Libraries and Setting Up I2C
- The machine module is imported to use I2C communication and Pin class.
- The time module is imported for adding delays in the program.
- The PCF8591 library is imported for easy interaction with the PCF8591 module. For more information about the PCF8591 library, please visit xreef/PCF8591_micropython_library.
```
from machine import I2C, Pin
import time
from PCF8591 import PCF8591
```
Initializing I2C Connection

I2C communication is initialized using SDA (Serial Data) and SCL (Serial Clock) pins. The Raspberry Pi Pico W uses GPIO 20 and 21 for this purpose.
```
i2c = I2C(0, sda=Pin(20), scl=Pin(21))
```
Initializing the PCF8591 Module

The PCF8591 module is initialized with its I2C address (0x48). This address might need adjustment depending on the module’s configuration.
```
pcf8591 = PCF8591(0x48, i2c)  # Adjust the address if needed
```
Checking Connection

The program checks if the PCF8591 module is connected correctly.
```
if pcf8591.begin():
    print("PCF8591 found")
```

Main Loop for Reading Analog Values

The program enters an infinite loop, continuously reading the analog value from channel AIN0.
The analog_read function is used to read the value from a specified channel.
The analog_write function is used to write the value to AOUT.
Jumper caps link the module’s potentiometer to AIN0, and the D2 LED is connected to AOUT. So the brightness of the LED changes as the potentiometer is rotated. Please refer to the PCF8591 module schematic for details.
A delay of 0.2 seconds is added between reads to stabilize the output.

while True:
    # Read and print the analog value from channel AIN0
    AIN0 = pcf8591.analog_read(PCF8591.AIN0)
    print("AIN0 ", AIN0)  # PCF8591.CHANNEL_0 can also be used
    # Additional channels can be read by uncommenting the following lines
    # print("AIN1 ", pcf8591.analog_read(PCF8591.AIN1))
    # print("AIN2 ", pcf8591.analog_read(PCF8591.AIN2))
    # print("AIN3 ", pcf8591.analog_read(PCF8591.AIN3))

    # Write the value back to AOUT. This will change the brightness of the D2 LED on the module.
    pcf8591.analog_write(AIN0)

    # Wait for 0.2 seconds before the next read
    time.sleep(0.2)