Basics about analog inputs of Raspberry PLC

Learning how to work with the analog inputs of the Raspberry Pi PLC
February 2, 2021 by
Basics about analog inputs of Raspberry PLC
Boot & Work Corp. S.L., Marti Guillem Cura


In this post, we are going to explain how to do the basics in order to work with the analog inputs of Industrial Shields Raspberry Pi programmable logic controllers. By reading this post, you will be able to understand how to connect, configure and work with the inputs of your industrial Raspberry Pi PLC controller.

Previous readings

We recommend you read the following posts to understand the programming of this blog. We have used the following blog posts for this example:

  • How to access the Raspberry Pi based PLC   Read >>

  • How to change the IP in Windows and Linux     Read >>


To work with analog outputs, you will need any of our industrial controllers for industrial automation:

Input types

On all Industrial Shields PLCs, analog inputs can work at:

  • 0 Vdc - 10 Vdc input

Each of them has a particular drawing in the case of the PLC:

Odoo - Sample 2 for three columns

0 - 10 Vdc Analog Input


How to work with Bash Scripts

Raspberry Pi industrial PLC has default bash scripts for working with the inputs. All the inputs and outputs scripts must be executed from the correct path. It depends on the shield type of the I/O executed. Depending on the shield of the I/O that you need to activate, you must execute the scripts from a specific path:
  • Analog/Digital Shields

> cd /home/pi/test/analog
  • Relay Shield

> cd /home/pi/test/relay

The get-digital-input script will show the value of the selected input pin. Only the pin we are going to work with will be provided. The return value will be in the range of 0 (0Vdc) to 2047 (10 Vdc). In order to call the function, we will do the following:

> ./get-analog-input <input>

Example for the I0.12 input returning a True value if it's receiving 10Vdc:

> ./get-analog-input I0.12

How to work with Python

The bash commands are the base for working easily with the industrial Raspberry PLC. In order to work with python files, if you want to interact with the IOs of the PLC, you will have to call these scripts.

To edit the files you will work with the Nano editor included by default and Python3.


Python allows you to execute a shell command that is stored in a string using the subprocess library. In order to work with it, you will have to import it at the start of the file.

import subprocess

In this example, you will be going to read the input given of the pin I0.12 of the Raspberry Pi PLC. In order to do it, you will implement a loop that will be constantly reading the input value.

import subprocess
import time

def str2dec(string):
	return (string[0:-1])

def adc(value):
	return (10*int(str2dec(value)))/4096

if __name__ == "__main__":
	while True:
			x =["./get-analog-input","I0.12"], stdout=subprocess.PIPE, text=True):
		except KeyboardInterrupt:

 In order to execute the Python program, you will call it as follow:

> python3

To exit the program, just press ^C.

Do you have doubts about the programming of our equipment?

 Our technical team will be glad to help you.

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Basics about analog inputs of Raspberry PLC
Boot & Work Corp. S.L., Marti Guillem Cura February 2, 2021
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