I am using the node 'serial in' from node-red-node-serial-port, to read data from the smart meter. This node is connected to a function node to process the data coming from the smart meter. It works well, but sometimes I get corrupted telegrams. I am trying to figure out how to do a crc-check on t…

@marcus-j-davies @Steve-Mcl As I said, I integrated the solution to my project, and it worked well. About 30% of the messages was corrupt. By now I also know the reason of the corrupt messages. Before I had a 4-fold hub between the smart meter and the pi. Later I removed that. After the removal the…

I'm not a pro, but to do a CRC check, the source of the data must provide one, and for you to do your own CRC check to ensure it matches with what was provided. So if the original data does not carry a CRC - you have no way to determine if its altered/currupted. I could be wrong here. EDIT The …

The value after the exclamation mark is the crc value. So in this case 6FEC.

Ok that makes things easier. Do you know the format of the CRC (8, 16, 32) etc? There are node libraries, that you can use to calculate the CRC of a value. Using such library, you can generate the CRC and check it with the provided CRC.

Nice! I was looking for a library to use as an example - you saved me having to do it. :pray:

@Steve-Mcl and @marcus-j-davies I first tried getting the telegram through the crc calculator. I tried all different ways, but no outcome returned a match. This telegram I tried, /Ene5\T211 ESMR 5.0 1-3:0.2.8(50) 0-0:1.0.0(231028193754S) 0-0:96.1.1(4530303632303030303130313639363232) 1-0:1.8.…

I have just put this together - it uses easy-crc [image] A Simple CRC Checksum Node (Subflow) Share Your Nodes This isn't a published node, but a subflow to easily validate checksums. The subflow requires the following inputs: crcLength : example : 8 crcCh…

@marcus-j-davies @Steve-Mcl [image] henkkas: I guess it must be crc16. What part of the telegram is crc calculated to get the good result? That seems to be from "/" until "!" included. See also my previous remarks about the calculator.

[image] henkkas: 668D I guess it must be crc16 Since it is a 4 digit WORD, I believe it will be a 32bit CRC. It could be a well known or a completely made up CRC.

@Steve-Mcl @marcus-j-davies I found a python programm that seems to do the trick. def calc_crc_telegram(telegram): x = 0 y = 0 crc = 0 #print "Lengte telegram",len(telegram) while (x < len(telegram)): crc = crc ^ ord(telegram[x]) x = x + 1 y = 0 while (y < 8): if ((crc & 1) != 0): crc = (crc >> 1) …

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Node serial port, how to perform crc check

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Steve-Mcl 28 October 2023 16:36 5

Assuming you know how to extract that CRC at the end of the data, you can likely use this solution to compute and verify it.

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Node serial port, how to perform crc check

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