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RevPi Connect 4

Product Description

The RevPi Connect 4 is a robust 24 V industrial PC for IIoT and automation projects based on the Raspberry Pi Compute Module 4. The RevPi is a basic module from the Revolution Pi family. All devices in the Revolution Pi family are developed in accordance with EN 61131-2.

Components

revpi-connect4-aufbau

PositionComponentApplication
1X2 connector RS485Serial Devices (RS485), Connecting the UPS
26 × status LEDLEDs
32 × RJ45 EthernetEthernet Interfaces, Establishing a Network Connection
42 × USB A 3.2 Gen 1USB Interfaces
5RP-SMA socket1WLAN and BT
6Micro USBSaving and Reinstalling the Image
7X2 connectorRelay output, Digital input
8X4 connectorConnecting the Power Supply
92 × locking clipMounting the Device on a DIN Rail
10Ventilation SlotsMounting the Device on a DIN Rail
112 × PiBridgeConnecting Expansion Modules
12Micro HDMISet up Desktop Mode

1 only for the variants with WLAN

Compatible RevPi Image
  • RevPi Bookworm Image
  • RevPi Bullseye Image

See: RevPi Images.

Variants

Item No.:RAMeMMCWLAN
1003762 GB8 GBNo
1003772 GB8 GBYes
1003784 GB32 GBNo
1003794 GB32 GBYes
1003958 GB32 GBNo
1003808 GB32 GBYes

For available variants see Revolution Pi Shop.

Extension Modules

The RevPi Connect 4 base module can be expanded by up to 10 expansion modules to create a Revolution Pi system:

Left sidebase moduleRight side
5 × RevPi I/O moduleRevPi Connect 45 × RevPi I/O module

Compatible I/O Modules

Virtual Devices

The Virtual Devices are delivered with the RevPi image as components in PiCtory included:

Scope of Delivery

The scope of delivery includes

  • RevPi Connect 4(base module)
  • X4 connector
  • 2 × X2 connector
  • 2 × cover plug for PiBridge
  • Supplement

Mounting and Connecting

The RevPi was developed for use in a control cabinet. Observe the specifications for the Intended Use and all Safety Instructions. Intended UseSafety Instructions

warning

Danger to life due to electric shock

There is a risk of fatal electric shock when working on devices in the switch cabinet with 230 V mains voltage.

▷ Work in the switch cabinet may only be carried out by qualified electricians.

▷ Before carrying out any work in the switch cabinet, switch off the power supply properly.

Carry out the installation and connection in the following order :

  1. Mount the RevPi base module and all expansion modules on a DIN rail.

  2. Connect the expansion module via the PiBridge connector.

  3. Connect all other devices such as sensors and actuators. The interfaces available to you for this can be found in the Componentssection.

  4. Connect a monitor and a keyboard if you want to operate the RevPi in desktop mode. This is not necessary if you can access the RevPi via a network connection.

  5. As the last step connect the power supply.

Connecting the UPS

A UPS (uninterruptible power supply) ensures that devices continue to function during a fault. Depending on the type of UPS, a UPS can protect against the following faults:

  • Power failure
  • Overvoltage
  • Undervoltage
  • Frequency changes
  • Harmonics

The RevPi has a digital input, to which the status output of a UPS can be connected.

▷ Please check whether your UPS is suitable for connection to the RevPi.

▷ Connect the status output of the UPS to the digital input on the X2 connector (pin IN and pin ⫠).

▷ Observe the installation specifications of the UPS manufacturer.

▷ Test the UPS.

In the process image, bit 6 of the RevPiStatus variable is 0 or 1, depending on whether 0V or 24V is applied to the input. Your application must read this bit cyclically. If the UPS reports a problem, your application must initiate a corresponding measure. What exactly should be done depends on:

  • the size of the battery used,
  • the current consumption of the RevPi,
  • the current consumption of all components that are additionally connected to the UPS.

Typically, the system is brought into a safe state and the RevPi is shut down.

Access to the Device

The RevPi is accessed in two steps:

  1. Establishing a Network Connection.

  2. Login on the device.

Install all available Updates as soon as the RevPi is connected to the internet, so that the system is always up to date with security-relevant features.

Alternatively, access is possible without a network, see Desktop Mode.

See also:

Configuration

Basic Configuration

From the RevPi Bookworm image (10/2024) onwards, the basic configuration of the RevPi devices is carried out via the Cockpit web application.

Until the RevPi Bullseye Image (04/2024), the basic configuration of the RevPi devices is carried out via the RevPi Status web application.

System Configuration

The Revolution Pi system, i.e. a RevPi base module with expansion modules, is configured via the PiCtory web application.

Configuring the Base Module in PiCtory

▷ Start PiCtory.

▷ Select the RevPi base module from the Device Catalog and drag and drop it onto the empty slot with position number 0.

     ❯ The configurable values appear in the Value Editor.

▷ Save the configuration as the start configuration with File > Safe as Start-Config.

❯❯ The start configuration is called up directly after each boot process.

ValueFunction
INP RevPiStatusStatus of the piControl driver
INP RevPiIOCycleCycle time of piBridge communication between base module and expansion modules in ms
INP RS485ErrorCntError counter for piBridge communication
INP Core_TemperatureCPU Temperature
INP Core_FrequencyCPU Frequency
OUT RevPiOutputOutput value for relay contact
OUT RS485ErrorLimit1First limit value for error counter > Message in kern.log
OUT RS485ErrorLimit2Second limit value for error counter > piBridge communication is stopped
OUT RevPiLEDStatus byte for LEDs

Serial Devices (RS485)

The RevPi has an RS485 interface on the upper X2 connector to connect serial devices such as sensors.

The socket has differential data line terminals P/N and reference terminals (internal GND and functional earth via 1 MOhm RC network).

revpi-connect-4-rs485-pinout

Under Linux, the interface can be addressed via the device driver node with :

  • /dev/ttyRS485

How you use this connection optimally depends on your project environment. The network you are working with or the EMC load are individual factors that influence how you assign this connector.

We are therefore unable to show you an optimal solution for your individual project, but we have compiled a list of the problems that can occur and tips on how you can solve them.

RS485 is a fully differential line and does not normally require a third GND line. However, due to the limits of the input receivers ("maximum common mode voltage"), there may be problems with the signal quality if no potential reference is used between the transmitter and receiver. However, connecting the internal GND to a line that is subject to EMC can lead to EMC problems within the RevPi Connect.

We therefore recommend that you use a common functional earth between all RS485 network participants. This gives you a good, common reference potential for the differential bus signal.

If this does not work either, you can connect the FE terminal of the RS485 connector to the third (GND) line of the bus.

You can also try to solve signal problems with the GND terminal.

Ethernet Interfaces

The RevPi can be connected to a network via the RJ45 interface.

Two 10/100 Ethernet connections are available on the RevPi, which are independent of each other. This allows the RevPi to be integrated into two different networks. The MAC addresses are printed on the front of the housing.

Under Linux, the interfaces can be addressed with:

  • Socket A: eth0
  • Socket B: eth1

WLAN and BT

Prerequisites

✓ RevPi base module with WLAN interface

✓ DHCP-capable WLAN router

✓ Optional: external RP-SMA WLAN antenna

The WLAN interface operates at 2.4 and 5 GHz and complies with the IEEE802.11a/b/g/n/ac specification.

Under Linux, you can address the WLAN interface with , provided no other WLAN devices are used:

  • wlan0

Activate WLAN via RevPi status

▷ Start RevPi Status.

▷ Activate the Enable/Disable build-in WLAN option in the CONFIG tab.

Restart the RevPi.

Set up WLAN country code via raspi-config

The regulations and frequency ranges for WLAN networks are different for each country. Configure the WLAN country code so that the RevPi does not transmit in prohibited areas or cause interference.

▷ Log in to the RevPi via a terminal.

▷ Open raspi-config with the command:
sudo raspi-config

▷ Use the arrow keys to navigate to the Localization Optionsmenu.

▷ Select the WLAN Countryoption.

▷ Select the appropriate country from the country list and confirm with ENTER.

Restart the RevPi.

❯❯ The WLAN country code is active.

Set up WLAN connection via NetworkManager

The WLAN connection is set up via the NetworkManager nmtui. The NetworkManager is a terminal-based user interface for managing network connections under Linux.

▷ Log in to the RevPi via a terminal.

▷ Start nmtui with the command
sudo nmtui

❯❯ The nmtui user interface appears.

Use the arrow and ENTER buttons to navigate within nmtui.

▷ Select Edit a connection.

▷ Select the appropriate Wi-Fi network.

▷ Enter the WLAN password under Password and configure any other WLAN settings.

▷ Save the settings with OK and return to the home screen with *Back *.

▷ Select Activate a connection.

▷ Select the Wi-Fi network and activate the connection with the ENTER button.

     ❯ The status message Connecting ... appears.

     ❯ The WLAN connection is established.

Setting up BT Interface

BT interface Standard 5.0 is also available via the same SMA socket as for the WLAN interface.

▷ Log in to the RevPi via a terminal.

▷ Activate the HCI interface with the command:
sudo systemctl enable hciuart

▷ Start the hciuart service with the command:
sudo systemctl start hciuart

▷ Start the BT daemon with:
sudo systemctl start bluetooth

See also:

USB Interfaces

The RevPi has two USB-A Interfaces. This allows USB 2.0 client devices such as USB hard disks, surf sticks, keyboards or mice to be connected. Both sockets together may be loaded with 1 A. How the current is distributed to both sockets is irrelevant. Z. For example, one socket can be loaded with 1 A and the other cannot be used. Or one socket is loaded with 300 mA and the other with 700 mA. For both connections together, 1 A must not be exceeded. If more than two USB-A ports are required, a USB hub can be connected.

LEDs

LED PWR

The PWR (Power) LED indicates the device status.

SignalFunction
GreenPower supply is connected.
RedThere is a communication fault between connected modules.

LED A1 – A5

LEDs A1 to A5 are customizable.

The LEDs can be used for user-specific requirements such as indicating a network connection, indicating that a memory limit has been exceeded, monitoring a process and indicating faults.

The LEDs can be switched in the command line application piTest with the variable RevPiLED.

The RevPiLED output has a defined byte length and therefore has a certain number of bits that are read from right to left. Certain bit positions are each assigned to an LED. The LED is switched by setting the respective bits to 0 or 1.

LEDAssigned bit position
A10 to  2
A23 to  5
A36 to  8
A49 to  11
A512 to  15

An LED signal is set in the command line with the command piTest -w RevPiLED,x where x corresponds to the decimal value calculated from the respective bit pattern.

LEDSignalBit patternDecimal value
A1 – A5off0000 0000 0000 00000
A1red0000 0000 0000 00011
green0000 0000 0000 00102
blue0000 0000 0000 01004
orange0000 0000 0000 00113
cyan0000 0000 0000 01106
magenta0000 0000 0000 01015
white0000 0000 0000 01117
A2red0000 0000 0000 10008
green0000 0000 0001 000016
blue0000 0000 0010 000032
orange0000 0000 0001 100024
cyan0000 0000 0011 000048
magenta0000 0000 0010 100040
white0000 0000 0011 100056
A3red0000 0000 0100 000064
green0000 0000 1000 0000128
blue0000 0001 0000 0000256
orange0000 0000 1100 0000192
cyan0000 0001 1000 0000384
magenta0000 0001 0100 0000320
white0000 0001 1100 0000448
A4red0000 0010 0000 0000512
green0000 0100 0000 00001024
blue0000 1000 0000 00002048
orange0000 0110 0000 00001536
cyan0000 1100 0000 00003072
magenta0000 1010 0000 00002560
white0000 1110 0000 00003584
A5red0001 0000 0000 00004096
green0010 0000 0000 00008192
blue0100 0000 0000 000016 384
orange0011 0000 0000 000012 288
cyan0110 0000 0000 000024 576
magenta0101 0000 0000 000020 480
white0111 0000 0000 000028 672

To switch several LEDs simultaneously, the respective decimal values have to be added up.

Example: If LED A1 shall flash red and LED A2 green at the same time, the command is piTest -w RevPiLED,17 (bit pattern: 0001 0001 = decimal values 1+16).

note

If a signal is to be added to an existing LED circuit, the value for all required signals must be recalculated and rewritten.

Watchdog

A watchdog is a timer that restarts the RevPi after 60 seconds. To prevent this from happening, the watchdog must be reset regularly as long as the system is running without errors. In the event of an error, such as a crash of the application process, there is no reset and the watchdog triggers a restart of the RevPi.

The RevPi has two independent watchdogs. There are several ways to use a watchdog under Linux. The RevPi image and Raspbian rely on systemd.

Integrated Watchdog

The watchdog integrated on the processor behaves like other watchdogs under Linux and can be addressed with:

  • /dev/watchdog0
  • /dev/watchdog (as standard watchdog)

External Watchdog

A second watchdog is available via the RTC module and can be addressed under Linux with:

  • /dev/watchdog1

See also:

Relay output

The RevPi has a relay output on the lower X2 connector. This relay output can be used, for example, to interrupt the power supply to connected hardware.

  • The relay can switch a maximum of 30 V and 300 mA.
  • The relay contact is open after the start.

▷ Make sure that all devices are disconnected from their respective power supplies.

▷ Connect the load to be switched to the OUT pins on the X2 connector.

▷ Connect the power supply.

The relay output is defined in the process image via the status byte RevPiOutput, Bit 0.

Digital input

The RevPi has a digital input for a +24 V input signal on the lower X2 connector. The input has an internal pull-down resistor.

The digital input can be used to connect a UPS.

▷ Make sure that all devices are disconnected from their respective power supplies.

▷ Connect the signal transmitter to the IN+ and IN- pins of the X2 connector.

▷ Connect the power supply.