The UniPi Neuron is a modular Programmable Logic Controller (PLC) product line, designed to be used as a central control unit for control, regulation and monitoring of smart building systems, HVAC (Heating, Ventilation, Air Conditioning) systems and industrial automation. Thanks to its modular architecture and compact design, the Neuron represents a highly flexible and affordable solution for quickly expanding field of smart technology. Customers can also utilize the Neuron for smart energy management to achieve better energy efficiency and reduce expenses.

The Neuron is suitable for:

Neuron is designed to be suitable for nearly every automatization project.



Each Neuron model is divided into one to three input-output (I/O) groups depending on model, each containing a group of input, output and/or communication modules. Each I/O circuit board is controlled by its own STM32 processor, which controls inputs and outputs and communicates with the central processing unit (CPU). Processors are using our own firmware containing not only basic I/O functions, but also additional functions and features. I/O modules of each group are labeled to minimize the risk of mismatch.


As the CPU of all Neuron units, the Raspberry Pi single-board computer is used. Each I/O group processor is connected to the CPU and to a central communication channel for all group processors. There is no communication between I/O groups. Each processor can also function independently on the CPU, allowing users to retain basic control of I/O modules in the event of CPU malfunction or software issue. The whole system is assembled into a grounded eloxed aluminium case with an IP20 degree of protection.

The following picture shows inputs, outputs and group labeling on the Neuron L40x-series unit:

Group 1 Group 2 Group 3



Thanks to their modular design, I/O boards are fully interchangeable. Thanks to that, a new model can be created by simply swap existing I/O groups or changing them for entirely new one, adding more functionality. We created 12 modules differing in number and type of I/O's with each of them being based on the S103 model - the core model of the whole line.

Currently, we have 12 models of Neuron PLC unit, which can be equipped with

  • up to 64 digital inputs
  • up to 4 digital outputs
  • up to 56 relay outputs
  • up to 9 analog inputs
  • up to 9 analog outputs
  • up to 3 RS485 universal bus ports
  • various combinations of the above-mentioned

Communication interface

As standard, all Neuron units are equipped with the RS485-Modbus and the 1-Wire communication interfaces. The 1-Wire low-speed is used for passive data collection from various attached sensors such as thermometers, humidity meters and other measuring devices. The 1-Wire low-speed data bus allows up to 15 devices with unique HW addresses to be connected to each channel. Modbus is then a communication protocol using the RS485 serial bus and serves as an interface for connecting and programming various devices sharing a given protocol. As standard, all Neuron units are equipped with one RS485 bus - the exception is the Neuron 500 line with up to 3 RS485 bus ports. These units then can be connected to devices using up to three communication protocols.

Inputs and outputs

Depending on model, I/O groups can be equipped with digital, analog and/or relay modules, or combination of all types. Each type has its own specific features and usage.

  • Digital inputs are designed for reading of binary values (0/1, on/off, open/closed etc.) and are thus suitable for connecting switches, motion sensors, window or door magnetic locks etc.
  • Digital outputs can be used to control binary state devices, such as lightning switches, window shutters control, remote door control etc.
  • Analog inputs are used to receive either 0-10V voltage or 0-20mA current signals. Alternatively, they can be used for reading data from corresponding sensors, such as resistance thermometers. The user can adjust the input mode via corresponding control software.
  • Analog outputs are used for control of external devices such as three-way valves or heat exchangers via 0-10V voltage or 0-20mA current signals. Analog outputs allow current or voltage regulation - alternatively, Group 1 inputs can be used in combination with resistance thermal sensors.
  • Relay outputs are designed for switching two-state devices via alternating or direct voltage. Relays thus can be used to switch boilers, water heaters, electric motors or other stronger relays. Neuron unit relays are designed for 5A maximum current and 250V alternating/30V direct voltage.

Extension modules

Aside from Neuron PLC product line, we also developed Neuron XS extension modules. These modules are based on the basic Neuron S103 unit, but the Raspberry Pi CPU is replaced by additional I/O group based on the particular model. Extension modules are connected via RS485 universal bus and can be used in combination not only with Neuron, but also with any other RS485-compatible PLC unit.

Depending on model chosen, extension modules can extend existing systems by following:

  • up to 24 additional digital inputs
  • up to 14 relax outputs
  • up to 4 analog inputs
  • up to 4 analog outputs


We designed the Neuron software to be as open as possible. The unit can thus use any solution from a list of native, commercial or open-source platforms for control, regulation and PLC configuration.

The basic software provided is the Linux OS along with the Modbus communication interface using TCP protocol - both can be downloaded freely from our website. This basic solution is designed for simple user application implementation and supports remote access along with running the software.

Native software platforms

Our main SW platforms are Mervis and EVOK. Mervis platform is a collection of tools and applications for advanced control and regulation. Apart from the control software, development application and user-friendly graphic interface are also provided, along with SCADA interface for remote control and monitoring. The platform was developed in accordance with the IEC 66131-3 standard for PLC software. Mervis is license-based.

EVOK is designation of our open-source application programming interface (API), designed primarily for remote access to our PLC units. It is a simple-to-use software allowing easy hardware access without the need for complex programming. EVOK is using six unified methods (or protocols), thanks to which the user does not have to write his/her own code. That means, any programming language can be used. These methods are:

  • REST Web Forms
  • Bulk JSON
  • SOAP
  • WebSocket

These protocols cover absolute most of existing devices and software, which makes the EVOK a highly flexible software acting as a layer between the device or software itself and the EVOK webpage containing the control interface. Resulting software is easy to use enough for absolute beginners to use it.

Software platforms supported

The Neuron supports the following software platforms


  • CoDeSys
  • Wyliodrin
  • HomeSeer HS3
  • REX


  • Jeedom
  • FHEM
  • PiDome
  • Pimatic
  • Domoticz
  • DomotiGa
  • Node-RED


Digital input and output modules of the Neuron feature a set of functions allowing the user to customize the unit's functionality.

Digital inputs contain Debounce, Counter and DirectSwitch functions.

  • Debounce automatically compensates for signal fluctuations through a control interval measured in milliseconds. The impulse is then evaluated as valid only if it lasts for a given control interval. By that, the Debounce can prevent multiple returns of a single impulse. A correct Debounce setting is vital for a proper digital input operation.
  • Counter function counts impulses received by the digital input and resets itself when a pre-set peak value is reached. With this function, the digital input can be used for reading data collected by digital flow meters, thermometers and other digital measuring devices.
  • DirectSwitch is a group of functions of digital outputs, allowing output's fast reaction to input state change, which is processed by a local processor of a given I/O group, bypassing the communication with the CPU. As a result, the device can achieve a very small latency. That makes the DirectSwitch a suitable choice for control of lightning or any other time-critical applications. Neuron XS extension modules are also equipped with the DirectSwitch functionality.
  • Digital outputs also support the pulse-width modulation (PWM) for transmitting two-value analog signals.

Other functions

  • The MasterWatchdog feature monitors the communication between CPU and local processor. If no exchange occurs within a pre-set timeframe, the MasterWatchdog automatically resets the device and I/O modules back into default settings.
  • Save default settings option allows each processor to save its default configuration. This configuration is then loaded after every device reboot triggered either by manual restart or by power outage.
  • Restart function provides user with option to trigger a restart of any I/O group and its reset back to default settings.
  • All Neuron models are also equipped with four customizable LED diodes. These are labelled as X1 - X4 and can be used as custom status indication.