Dobrý den pane Novotný,
ve zkratce - ano, je to možné a nepotřebujete na to ani Mervis.

Součástí operačního systému, který dáváte na kartu, je ModbusTCP server, přes který můžete ovládat veškeré vstupy-výstupy vyjma sběrnice 1-Wire. Tento server není typicky dostupný zvenčí ale je možné jej přenastavit tak, aby byl dostupný na portu TCP/502. Můžete tak k PLC jednotce, která se chová jako Modbus Slave, přistupovat z libovolné aplikace, která Modbus podporuje (například pomocí zmíněných Java knihoven). Seznam Modbusových registrů a coilů naleznete zde.

Druhou možností je použít API našeho softwaru Evok, kterým taktéž můžete ovládat celou jednotku a to včetně zařízení na sběrnici 1-Wire.

Tutoriály na tyto způsoby komunikace budeme připravovat v následujících týdnech.

S pozdravem,
Martin Kudláček

Hi Jonathan,
do you have some touch screen from previous installation, or do you plan to purchase a new one? Generally speaking, the touch screens in industrial automation are equipped with PC (Pro-face for example) running custom HMI software, which communicates with PLC e.g. via Modbus. In this case, you can use Axon with no problem.

@boy-lenssen And I really recommend you to purchase the USB-RS485 converter. It is extremely handy for such debugging and it costs around $1 on eBay.

Dobrý den Dalibore,
toto je velmi jednoduché. V MervisIDE přidáte na PLC "Serverový kanál" a nastavíte protokol na ModbusTCP. Přidáte serverové zařízení, nastavíte mu IP adresu, port a modbusovou adresu, na které bude přístupné. V detailu zařízení pak namapujete registry a coily na příslušné proměnné. K proměnným pak přistupujete přes síť z libovolného Modbus Master zařízení / programu.

Místo ModbusTCP je možné použít i ModbusRTU, kde nakonfigurujete příslušný RS485 port a nastavíte modbusovou adresu.

Nemám ověřenou funkcionalitu na starém IDE (2.0.x), ale v novém, které bude začátkem září je toto plně funkční.

Martin

Hello @jakub, the pin header of the Raspberry Pi inside of the Neuron is not accessible and there is no space inside of the Neuron for such additional devices.

Hello @cvrcejir,
unfortunately this is an error in the REST API, not the Evok's web interface. I forwarded this issue to the programmers and let you know once it is fixed.

Thank you for your patience,
Martin

Hi @Martijn-Hemeryck,
it depends what type of output your sensor has. Basically there are PNP (sourcing) and NPN (sinking) outputs.

• PNP (sourcing) typically outputs supply voltage of the sensor when the sensor is in ON state otherwise it is unconnected (high impedance).
• NPN (sinking) shorts the output against GND when the sensor is ON, otherwise it is unconnected (high impedance).

For example digital outputs on our units are NPN.

If your sensor has PNP output and its supply voltage doesn't exceed 24V, you can typically connect it directly to the UniPi's digital input.

If your sensor has NPN output, that's where it gets a little bit tricky. Digital inputs can only distinguish the ON state (voltage 5-24V). Any other state - be that 0V, short to the ground or high impedance (nothing connected) will result in OFF state. In order to use NPN sensor, you need to define the OFF state by connecting the NPN output to supply voltage via pull-up resistor. And there are two ways how to do it, depending on the supply voltage of the sensor

The pull up resistor will bring the OUT to the level of the supply voltage. In the first example it is 24V, in the second example it is 12V. The GND of the UniPi and the GND of the second power supply may or may not be connected, depending on the level of isolation you need between UniPi and the sensor. But that's another story. But the DIGND has to be connected in both cases.

Martin

Hello @stevenhendrickx,
I'll start from the end - the RaspberryPi running an InfluxDB. I can only guess - and correct me if I am wrong - but you have only SD card with the Raspbian in your RaspberryPi, right? The SD cards are quite fragile regarding the number of data you can write on them. That's the reason why we switch the filesystem in MervisOS to read-only. So generally, running a database on the SD card is not-so-good idea.

Now to the part how to access Mervis variables from outside. Currently the most straightforward method is via Modbus. If you haven't use Modbus before, please take a look on the protocol itself: physical layers, addressing, datatypes,... The Wikipedia article is a good (a bit too complicated) start.
Then check our tutorial how to setup ModbusTCP server (slave) in Mervis: https://kb.unipi.technology/en:sw:01-mervis:setting-modbus-server-hidden
And to put it together check this Python Gist how to poll data from ModbusRTU slave into InfluxDB: https://gist.github.com/sansal54/bea2526ab8e968351a85db3410cc9f65

There's a lot of information you need to grasp from the beginning to get it working. Feel free to ask more.

Martin

Hi @martijn-hemeryck,
some of the dependencies are quite tricky and we weren't able to handle the transitions between new package names gracefully. The repo is reachable, however the URL has to end with slash: https://repo.unipi.technology/debian/

Best regards,
Martin

Hello @rtatibouet,
the RS485 and RS232 are completely different buses.

The RS485 is differential and doesn't need the GND, since the logic levels are based on the voltage difference between A and B terminal

The RS232 is not differential and the TX / RX logic levels are based on the voltages between TX and GND and RX and GND.

Best regards,
Martin

Hello @FabioIT, we have updated the tutorial on measuring the resistance: https://kb.unipi.technology/en:automation:02-glossary:analog-inputs-hidden#measuring_resistance

Hello @Stoeffel,
the Evok 2.3.0 with support for xG18 has been released. You can proceed with the apt update && apt install evok.

Using the xG18 is definitely more stable. Each sensor has its own dedicated port and the powering of the sensors is parasitic, which ensures that the sensor will lose the power and "reset" itself after each reading. Another great advantage is that you don't need to configure the IDs of the sensors, so replacement is very quick.

Best regards,
Martin

Hello @Stoeffel,
the xG18 is not yet supported in the current version of Evok. We will publish the new version of Evok today or tommorow. I'll let you know, once it is out.

Thank you for understanding and have a nice day,
Martin

Hi @HonzaS,
the problem is that there are effectively two processes accessing the same serial port, which by definition is not possible. One process is the Evok communicating with the xS11 and another process is the Node-RED communicating with the energy meter.

You have to combine these two under one "hood". Configure the energy meter as a custom prototype in Evok, or disable the xS11 in Evok and read it via Node-RED.

Best regards,
Martin

For the record - @r3sist discovered that the corrupted SD card has been causing the delays. Everything in the program has been configured correctly.

There is something really wrong int the project @r3sist. Please send it to support@unipi.technology. With my project in ST code I am able to run on 20ms.

Hello @clueless,
the 1-Wire addresses are uploaded to the PLC with Deploy od the solution.

Hello @juntiedt,
the best way is to use the 3 wire sensor as the last one and connect the data line to the pin 6 on the RJ45 connector. Please consult this tutorial: https://kb.unipi.technology/en:automation:02-glossary:1wire-hidden

Hello @juntiedt,
the Unipi 1.1 doesn't have RS485 interface, so you need to use some RS485/USB converter. The latest Evok has support for xG18, you just need to set it in the /etc/evok.conf as a normal Unipi Extension.