I have a EM24 Ethernet as part of an ESS. Is it possible to gather data from the EM24 via nodered through one of the Victron nodes?
If not, is there an example anywhere of how to poll data from the EM24 Ethernet in parallel to the GX via Modbus TCP from nodered?
...most lightweight approach with node-red would be to use mqtt, as this comes natively with it.
Just enable mqtt in the GX and check, i.e. with mqttexplorer what the GX publishes to its broker and which topics you want to subscribe to.
Enable the GX to publish the required topics with keepalive.
See: https://github.com/victronenergy/dbus-mqtt#keep-alive
works perfect. thank you so much.
Using modbus tcp it would look like this
The left node is "Modbus-Read" is configured like in the picture below.
https://www.enika.eu/data/files/produkty/energy%20m/CP/em24%20ethernet%20cp.pdf describes the modbus registers to read. "Sum W" is under address 0028h which is 40 in decimal and consists of 2 16bit words.
Converting those two words to a valid 32bit Integer Value can be done like this in the JavaScript function block:
var rawData = new ArrayBuffer(4);
var intView = new Uint16Array(rawData);
var int32View = new Int32Array(rawData);
intView[0] = msg.payload[0]; //low
intView[1] = msg.payload[1]; //high
msg.payload = int32View[0].toFixed(1)/10.0;
msg.topic = "power";
node.status({fill:"blue",shape:"ring",text:msg.topic + ":" + msg.payload});
return msg;
Of course the dbus-mqtt solution is much more elegant.
with the contents
nice. Note, that IMHO with modbus read node, the conversion in the function node could me much more simple, when using the Response Buffer, not the data-bytes.
This is for a Bernecker MPM3PM meter, that I use outside of the victron ecosystem/GX.
For a signed 32bit BigEndian Buffer, coming from the modbus-read node, this is what I do:
var W = 0; W = parseInt(msg.responseBuffer.buffer.readInt32BE() / 100); msg.payload = W; return msg;
You can also use the Victron node grid meter the EM24 Ethernet publishes a few basic values in that node which might be just what you need.
I recently spent a few days trying to understand how to read a 32-bit signed integer (INT32) from a Modbus device using Node-RED, as I had no prior experience with Modbus. I want to share my findings to help others who might encounter a similar situation.
To read a 32-bit signed integer (INT32) from an EM24 using Node-RED, follow these steps:
Here's an example of how to process the Modbus data in Node-RED using a function node:
const lsw = msg.payload[0];
const msw = msg.payload[1];
const uint16Array = new Uint16Array([lsw, msw]);
const int32Array = new Int32Array(uint16Array.buffer);
const result = int32Array[0];
msg.payload = {
Watt: result
}
return msg;
Node-RED:
Note the two registers in the Response node: 192; 0
Modbus Read:
https://gavazzi.se/app/uploads/2020/11/em24_is_cp.pdf
28h is hex for 40
