How to communicate Raspberry Pi 4 B+ with a MAX485 module

Industrial Arduino M-Duino working with Raspberry Pi board for industrial automation
May 20, 2019 by
How to communicate Raspberry Pi 4 B+ with a MAX485 module
Serzh Ohanyan



In this post, you will learn how to communicate a Raspberry Pi 4 B+ with an M-Duino by RS485 using a MAX 485 module.

Requirements for communicating Raspberry Pi 4 B+ with a MAX485 module

MAX485 Module Pinout

MAX485 Module

On-board MAX485 chip is a low-power and slew-rate-limited transceiver used for RS485 communication. By adopting half-duplex communication to implement the function of converting TTL level information into RS485 level, it can reach a maximum transmission rate of 2.5 Mbps.


Depending on RE and DE connection, the module works as a receiver or transmitter. Connected to VCC, it transmits data and connected to GND it receives data.

It is a cheap module. Batches of 5 units can be found for less than 1€.


Raspberry Pi to MAX485

Raspberry Pi 4 B+ Pins
MAX485 Module Pins

        MAX485 to M-Duino/Ardbox

MAX485 Module Pins
M-Duino / Ardbox Pin
3.3 V
The GPIO 17/27 digital pins are used to establish the type of communication.
Receiver or transmitter mode. 

Raspberry Pi 4 B+ Pinout

Raspberry Pi 3 B+ Pinout


Diagram of Raspberry Pi 3 B+ with MAX485 module

Python Code Example

In this example of code, we send a character from the PLC to the Raspberry Pi. Print it, and answer to the PLC with the same character, which is an "echo". Note that in the case of receiving data, pins 17 and 27 are deactivated and activated in case of transmitting data.

#!/usr/bin/env python3

' IMPORTANT: remember to add "enable_uart=1" line to /boot/config.txt

from gpiozero import OutputDevice
from time import sleep
from serial import Serial

' RO  <-> GPIO15/RXD
' RE  <-> GPIO17
' DE  <-> GPIO27
' DI  <-> GPIO14/TXD

' VCC <-> 3.3V
' B   <-> RS-485 B
' A   <-> RS-485 A
' GND <-> GND

re = OutputDevice(17)
de = OutputDevice(27)

' enable reception mode

with Serial('/dev/ttyS0', 19200) as s:
	while True:
		' waits for a single character
		rx =

		' print the received character
		print("RX: {0}".format(rx))

		' wait some time before echoing

		' enable transmission mode

		' echo the received character

		' disable transmission mode

Take a look at the Programmable Automation Controller based on Raspberry Pi

Automation, monitoring and control with the power and speed of the Raspberry Pi

Odoo • Image and Text

With double RS-485 ports, a double Ethernet port, UPS that will ensure a minimum power supply, this will secure a safe shut down and SD data protection. Also, a CAN bus. 

A PLC with the power of Raspberry Pi.

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How to communicate Raspberry Pi 4 B+ with a MAX485 module
Serzh Ohanyan May 20, 2019
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