Revolution Pi Questions And Answers

Obsolete knowledge is moved to the Legacy knowledge base



Would it be possible to simulate a RevPi IO Module? How can I do this?

  • It is possible via RevPiPyLoad, take a look here:

Is there an easy way to exchange data between a RevPi device and a Raspberry Pi?

Yes, use SSH keys and execute the commands on the remote device over the network.


How do I write/run a custom C-program that runs as the main control program?

I want to create a gateway application that exchanges data between HTTP and Modbus TCP slave, how does it work?

Is there a simple example of how I can control the LEDs of a Revolution Pi device directly from a Python program?

I would like to use a python program to read all inputs and write the read values from inputs back on the 8 analog outputs. Is there sample code on it?

I want to write a code by using a keyboard input to control an output using a variable “LM”, how do I do that?

You may need to save your PiCtory change and perform a driver reset, then you should be able to access the variable “LM” like so:

piTest -w LM,1

Or via Python and the popular Revolution PiModIO2 library. See the “BitMirror” forum for examples:

Can I access the process image with .NET?

Yes, but this application is beyond the reach of KUNBUS.


How can I automatically boot into the graphical desktop without having to log in?

  • There is the command “sudo raspi-config” see here:

Would it be possible to use the Revolution Pi in kiosk mode?

  • Yes, take a look here

  • Or how you can start a slideshow

  • Or here is a discussion


There was an abort when creating an image. Can I still log in again?

  • Yes, when you create an image, aborting is not a problem.

Would it be possible to enhance security to prevent my data from being stolen from the storage, i.e., by encrypting the eMMC storage?

  • No, it isn’t possible to use disk encryption for the eMMC storage. Depending on your use case, physical access restriction might be an alternative.

  • I would suggest asking in our community forums how others might solve this issue:

Cron Jobs

I would like to define a cronjob. What is the best way to do this?

Take a look here


I log in via SSH and want to start the graphical user interface with "startx", but I get a cryptic error message. What am I doing wrong?

Please use an HDMI monitor and a USB keyboard instead of SSH. It is not possible to start the graphical user interface with an SSH connection.


I am having an issue, a flood of "piControl: piControlI/O:missed x cycles" in the journalctl and dmesg logs, what can I do?

  • Check if all PiBridge connectors are connected tightly

  • Update your system as follows:


I am using RevPi Connect 4. Can I use PROFINET on the controller with the existing 2x network ports without gateways?

  • Yes, the 2 Ethernet ports of the RevPi Connect 4 can be used with CODESYS to implement different field buses like PROFINET, EtherNet/IP, EtherCAT.

I am using the Bullseye image, and my Modular Gateway is no longer recognized, what can I do?

Update your system, i.e. via “sudo apt update && sudo apt upgrade”

I would like to use the Revolution Pi Con CAN module without CODESYS, is this also possible?

  • Yes, this is possible, for example, with this tutorial:

  • Here the original discussion

Fetch repository fails, what can I do?

Have a look at the follwing link:

I want to use Controller Area Network (CAN) what device(s) can I use?

I need an EtherCAT master for our test field setup. I wonder if we should take a Revolution Pi as a speedy solution for this?

  • Yes, this is possible, take a look here

To receive data from a PLC via EtherCAT, do I need the EtherCAT extension module in addition to the Revolution Pi Connect + or can the whole thing be set up without the EtherCAT module?

Would it be possible to use the Revolution Pi Connect as an Ethernet/IP Master?

Yes, thanks to a soft PLC this is possible, e.g., with CODESYS:

I use a Modbus RTU with the uModbus library. Now there are communication errors at irregular intervals. What can I do?

  • Only low-level debugging can help. Please create, e.g., with an oscilloscope or a logic analyzer traces for the analysis of the signals on the RS485 interface. Are there cyclic or sporadic disturbances, etc.? What does the image on the RS485 interface actually look like?

Can I operate several Modbus RTU masters, simultaneously?

  • Yes, it works with various USB-RS485 interfaces. These are then addressable via “/dev/ttyRS485” and “/dev/ttyUSB2” for example.

There are Modbus registers which can be read but not written. What am I doing wrong?

If it is about Holing Register, the behavior is correct.

How can I transfer PROFIBUS data with a Modular Gateway PROFIBUS?

Would it be possible to operate a Revolution Pi device as a PROFIBUS master instead of a slave?

  • No, unfortunately this functionality does not exist at the moment.

Can I operate a PROFINET controller with the Revolution Pi Core/Connect/Compact/Flat?

Yes, this is possible. e.g., with CODESYS


Where can I find the UL certification for the RevPi Core S?

Take a look at the forum entry in the link below:


I copied an image and have network issues on both devices, what can I do?

  • This guide covers such topics

Is there a way to automate the process for producing devices?

  • There is a script in the forum without the claim of production suitability.

I have around 50 Revolution Pi Core 3+ here with me. Is there a way to replicate these settings and software onto all other Revolution Pi's that I have?


Can somebody propose a working solution to access the PLC running CODESYS over the internet?


Are licenses to be considered when Revolution Pi products are used in commercial applications outside KUNBUS?

I have purchased a Revolution Pi feat. CODESYS. Now I lost the CODESYS license because I reflashed the image, what can I do?

Please send us the following information to

  • Your invoice copy

  • Serial number. You can find this information here:

We’ll restore your CODESYS license.


Are the installation clearances always to be observed, even for individual modules (Core, Connect, etc.)?

Yes, we recommend these minimum clearances to ensure sufficient air flow around the enclosure when the Revolution Pi modules are mounted on a top-hat rail.

Excessive temperatures can damage your module.

Make sure that the ambient temperature in the control cabinet is less than 55 °C.


I would like to use an HDMI touchscreen monitor. Are there any recommendations?

  • Without conveying a preference, I can say that we offered monitors from Faytech in our online store.

  • However, we have benevolently removed them again, as well as other additional items to focus on the core business.

Can I tap into an existing serial communication?

  • Yes, it may be feasible. There is a discussion here:


I want to start a simple Webcam Stream to monitor a process. It’s works with Raspberry Pi 4 but not with Revolution Pi Core S Module 8 GB. How can I do?

Are there any examples of how to implement interrupts in the Revolution Pi?

Unfortunately, there is no implementation which interest as possible, Our source code is public. The interfaces are documented and freely available in our GitHub repository:

How to read the value come from X2 connector of Revolution Pi Connect with Python?

Is there a C# library available to access the process image?

  • Yes, take a look here:


Would it be possible to boot Ubuntu on a RevPi device?

Yes, see here ​RevPi3 on Ubuntu - Revolution Pi Forum


Are CAD models of the products available?

  • No, but there are STEP files in the download area.

What is the Export Control Classification Number (ECCN) for the Revolution Pi Connect module (PR100337)?

  • It is "5A992.C".

Are there user manuals?

  • No, CE and other declarations of conformity can be found in the download area:

Does KUNBUS also provide macros for EPLAN P8?

  • No, however, we have STEP files online.

I would like to rebuild the top hat rail setup from Dirk's video tutorials – are there dimensions for this?

Where can I find photos of the Revolution Pi from bottom, top, rear, and right?

Take a look at the online shop, rotate the modules, and you can grab yourself pictures, i.e., via


Would it be possible to operate negative switching outputs?

  • No, but with additional relays, this negative switching can be created.


What is the default login and password on the default image?

Use "pi/raspberry". Please note that if you want to log in with a keyboard and HDMI screen, the default layout is English (QWERTY).

I can't log on to the shell - what am I doing wrong?

How do you log in to the system? Possibly via HDMI screen and USB keyboard? Then it may be due to the English keyboard layout of the target system. So QWERTZ or QWERTY.

I am unable to login via SSH, but I am able to log in via Web Status, what can I do?

Where to find the credentials for the Revolution Pi Connect module?

It should be printed on the side of the device.


Are the Modular Gateway devices all slaves? How can a PROFINET Master be operated with the Revolution Pi?

Yes, the Modular Gateway modules do not have master/controller functionality. They function as slaves.

Yes, you can run a PROFINET Master not with the Modular Gateways but, e.g., with CODESYS:

Are the devices that are compatible with the Revolution Pi Core also compatible with the Revolution Pi Connect?

I am interested in the M-Bus module, is there any information?


How do I set the hostname?

Please try to set the hostname with:

sudo raspi-config

How can i change the Mac address permanently?

RevPi Core / Core 3(+) / Core S (until Revision 1.0) / RevPi Compact / RevPi Connect (+) / RevPi Connect S / RevPi Connect SE:

The mac address is set during factory reset and can be changed afterwards by modifying the file /boot/config.txt. The dtparams eth0_mac_* (and eth1_mac_* on Connect and compact) are read from the kernel driver.

RevPi Core S (starting with Revision 1.1) / RevPi Core SE / RevPi Connect 4:

The mac address is written into an eeprom, which is attached to the ethernet controller. The mac address can be changed (written into the eeprom) with the tool /usr/sbin/revpi-set-mac (part of package revpi-tools).

NOTE: The mac address for wlan0 and eth0 on Connect 4 are set differently, as the controllers are directly attached to the compute module. These mac addresses are set via an udev rule. See section revpi_connect4 in file /lib/udev/rules.d/50-revpi.rules

How to configure connect 4 to a Wi-Fi Network?

Please refer to this article .

How to set a static IP address under Bullseye?

The dhcpcd is no longer used since the Bullseye release and the NetworkManager is used instead. You can find more details on the changeover in the release notes of the first Bullseye image. The IP must therefore be configured in the NetworkManager. If you activate the dhcpcd, it gets in the way of the NetworkManager.What knowledge can we derive from it?

Network port not available – how can I use it?

  • Take a look at this discussion

How can I configure two different networks on the Revolution Pi?

  • Watch this video tutorial #6 explains how a network configuration works with two networks:

I have a Revolution Pi Connect and would like to use the two Ethernet sockets on the device as a switch. Is it possible and how?

Yes, it is possible. You can combine the two ports into one bridge. The necessary steps can be found here:

Is there a default IP address after booting?

  • No, the Revolution Pi is by default configured using DHCP

  • If you want to set up a static IP address, take a look at Video Tutorial 07 – Static IP Address

  • The RevPi Connect 4 uses mDNS, which makes it easier to locate the device in the network

I am using a Revolution Pi Flat module. How can I check if the Eth0 interface is working or defective?


How can I convert Sensor data in Node-RED?

You can see an Example, how to convert data from a pressure sensor. The sensor has a range from 1V to 5V and a measuring range from 0kPa to 2kPa.

See here: Sensordaten umrechnen - Revolution Pi Forum


Our PLC can possibly be activated as an OPC server, can the Revolution Pi Connect work as an OPC client?

  • If the Raspberry Pi can do it, so can the Revolution Pi.

  • KUNBUS doesn't have any shares in it, but the possibility is certainly there to run entirely different OPC servers or clients on Revolution Pi devices


Can I modulate a signal with the maximum cycle time of the Revolution Pi DIO bridge, around ~2.5ms?

  • No, but it would work with the Revolution Pi Compact, where we allow 250 usec cycles for the digital I/Os and analogue outputs.

  • The Revolution Pi DI/DO/DIO modules cannot be used for such applications due to the limitation of the PiBridge communication cycle.

How can the cycle time of the PiBridge be measured?

Would it be possible to read Revolution Pi Analog Input in microvolt?

  • No, the sampling in microvolt is not possible but with the Revolution Pi Compact, there is a workaround to increase the sampling frequency.


Would it be possible to down clock the CPU frequency of a Revolution Pi Module?

  • We cannot recommend down clocking the CPU. This means that the functionality of PiControl can no longer be guaranteed correctly.

I heard the CM3 module has only one gigabyte of RAM, is that true?

Would it be possible to connect multiple Revolution Pi Core modules with the PiBridge?

Yes, this is technically possible, but without official support. The two network interfaces “pileft” and “piright” are available in the system. Via these two interfaces, a network can be configured between two communication partners that are connected via the PiBridge.


Revolution Pi Core #1

Right PiBridge

Left PiBridge

Revolution Pi Core #2

Network Interface





Take a look at Tutorial 07 – Static IP Address:

Can Revolution Pi retain the last value state when power rev pi is off?

  • No, the Revolution Pi doesn't retain the last value when power is off (except for the real-time clock, which is buffered for 24 hours).


I have questions about PiBridge communication, where can I find details about this?

Take a look at the PiBridge driver source, it's pretty well commented.

I am curious about the RSC files, is there a documentation?

  • Yes, take a look here

  • There is a fruitful discussion about the documentation of the RSC files and types in it

Real time

The pl011_pio_tx process generates a CPU load of consistently about 20%. Is this behavior plausible?

  • The process “pl011_pio_tx” is a sub process that is responsible for the data exchange between the modules and Revolution Pi. This requires about 20% of the CPU resources.

  • There is nothing you can configure about this behavior.

How can I create a real-time program?


What is the maximum baud rate for RS485?

  • The standard value of the baud rate is 19200. No threshold is defined for the RS485. You must proceed randomly to define the maximum baud rate threshold that suits you.


I want a Trusted Platform Module (TPM) what device can I use?

  • Revolution Pi Flat Module


When I log in to WebStatus I get an error message after a short time, what am I doing wrong?

If you have upgraded your system, you are probably missing the correct web server configuration:

I cannot log in to WebStatus, error message "ERROR: There is no enough free disk space - click for support". What can I do?

  • You can try logging in via SSH and deleting unnecessary data and applications to free up memory.

  • Original discussion here

How to easily upgrade from Buster to Bullseye?

# update Buster to latest patch leven sudo apt update sudo apt upgrade # update repositories (buster -> bullseye) sudo sed -i -e 's/buster/bullseye/g' /etc/apt/sources.list sudo sed -ie 's/buster/bullseye/g' /etc/apt/sources.list.d/{raspi,revpi}.list # fetch package list from updated repositories sudo apt update # install dependencies sudo apt install libgcc-8-dev gcc-8-base # remove webstatus due to conflicts (will be reinstalled later) sudo apt remove revpi-webstatus # perform upgrade stage 1 sudo apt upgrade # reinstall webstatus sudo apt install revpi-webstatus revpi-webstatus-redirect pictory # perform upgrade stage 2 sudo apt full-upgrade # Enable network manager instead of dhcpcd curl -o /tmp/ cat bash /tmp/ # ensure that local network configuration is migrated, if something else than dhcp is used ! # reboot RevPi sudo reboot

Are there integrated development environments available?

RPiBoot.exe aborts the installation with a “TrustedPublisher” error, what can I do?

  • Disable the Driver signature verification.

The tool is from the Raspberry Pi Team and can be downloaded on their website.


GitHub Link:

How can I install OpenVPN Client?

Can I use TeamViewer, and what happened to TeamViewer-Revolution Pi?

TeamViewer-Revolution Pi has moved to a new product called TeamViewer-IOT. Take a look at Video Tutorial 24.1 – TeamViewer IoT for a brief introduction.

I would like to confirm that we can program G Code on Revolution Pi?

I want to use OpenPLC and I heard that is possible, is this information true?

  • Partly because KUNBUS does not guarantee or support the functionality. However, there are first successes, see here:

I would like to use the robotics programming language ROS for a project. How can I implement this with a Revolution Pi product?

Please take a look here, maybe you get your answers for installing ROS

Our image is derived from Raspbian, perhaps you get further instructions here

Or here


Can I use the Con CAN SPI interface for my application?

  • Yes, this is possible with a few steps. Take a look here:


Would it be possible to read the same PT100 thermistor with two Revolution Pis? How are the internal resistances of the pins for RTD measurement?

The resistance between the pins is 100kOhm. The resistance between the RTD pins of the two Revolution Pis is also 100 kOhm. The PT100 has a maximum of 3kOhm. You can calculate the influence of 100kOhm on 3kOhm with an error calculation.


How can I update the time on the RevPi module?

  • Usually, time is synchronized automatically. You can check the status via

  • The Bullseye image uses UTC as the system timezone. For previous images, you can manually change it by running:

How do I set up my time-server


Is there a way to ensure that the USB devices are always represented with the same device file names?

  • Yes, there are “udev rules”.

I have connected several USB serial adapters to a RevPi module, but only one of them is displayed in the /dev/serial/by-id path and only /dev/serial/by-path/ is generated. What can I do so that both devices are displayed?

  • Please update your device so that the UDEV rules are up-to-date.


I am new to the RevPi Connect 4 Module and the watchdog functionality. Do you have an example?

My Revolution Pi device continues to restart, what can I do about it?

  • Please check the watchdog jumper at connector X4.

Web Status

I can't log into Revolution Pi Web Status, the page continues to reload, what can I do?

We just uploaded a fixed version of RevPi-tools (2.0.1-1). After an update via “sudo apt update && sudo apt upgrade” everything should work as expected.


I can't connect to a Wi-Fi network with the RevPi Connect 4, what can I do?

Please check if the Wi-Fi network is compatible (WPA3 is not compatible).

Is a Revolution Pi module able to send an SMS?

  • No, unfortunately, there is no native SMS functionality. You can use a web-based SMS service which is called from your software on the Revolution Pi module (requires internet access). Another way is to attach a hardware modem that offers that functionality.

Is there also a wireless connection to integrate a Revolution Pi into our network, e.g., 4G Wi-Fi, UMTS, etc.?

I would like to use a compatible Wi-Fi dongle, do you have recommendations?

Yes, just take a look at these pages

The Wi-Fi USB dongle MAC address changes every power cycle, what can I do?

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