Example Code for Raspberry Pi-Analog Read

Hardware Preparation

• 1x DFR0604 IO Expansion HAT for Raspberry Pi, Purchase Link
• 1x Analog Sensor
• 1x Raspberry Pi

Software Preparation

1. To use the analog and PWM ports in the board, download the driver library first. Press Ctrl+Alt+T to open the terminal, input the following command and hit Enter.

   git clone https://github.com/DFRobot/DFRobot_RaspberryPi_Expansion_Board.git  
   

2. Download the library and unzip the file. Input the following command into the terminal:

   tar -xvzf DFRobot_RaspberryPi_Expansion_Board  
   

3. Enter the directory of the uncompressed files:

   cd DFRobot_RaspberryPi_Expansion_Board/raspberry/  
   

4. Use nano editor to create and edit the code file.

Wiring Diagram

• Plug the IO expansion board into Raspberry Pi.
• Connect an analog sensor to Analog P0.

Other Preparation Work

Create a file for the analog test (e.g., using nano: sudo nano analogTest.py) and add the sample code.

Sample Code

analogTest.py

# -*- coding:utf-8 -*-
# analogTest.py

import time
from DFRobot_RaspberryPi_Expansion_Board import DFRobot_Expansion_Board_IIC as Board

board = Board(1, 0x10)  # Select i2c bus 1, set address to 0x10

if __name__ == "__main__":
  while board.begin() != board.STA_OK:  # Board begin and check the board's status
    print("Board begin faild.")
    time.sleep(1)
  print("Board begin success.")

  board.set_adc_enable()
  
  while True:
    print("Read part of channels.")
    val0 = board.get_adc_value(board.A0) # channel A0 is readed
    '''
    val1 = board.get_adc_value(board.A1) # channel A1 is readed
    val2 = board.get_adc_value(board.A2) # channel A2 is readed
    val3 = board.get_adc_value(board.A3) # channel A3 is readed
    '''

    print("channel:A0, value:%d" %val0)
    '''
    print("channel:A1, value:%d" %val1)
    print("channel:A2, value:%d" %val2)
    print("channel:A3, value:%d" %val3)
    '''
    print("")
    time.sleep(1)

The function board.get_adc_value() in the example is used to get the value of analog port, the pin selection list is shown below:

Result

The terminal will output the analog value read from channel A0 every 1 second, e.g.

• "channel:A0, value: 512".

Additional Information

The IO expansion board comes with an on-board MCU STM32 that provides 12 bit ADC. The voltage of analog sensor will be input into the 12-bit ADC sent to Raspberry Pi via IIC when the analog data is converted into digital data, by which to allow Raspberry Pi to read values of analog sensor.