CRC Error

[lgr]

Hi, erevryone!
I have a problem,
SCADACommService make a wrong CRC:
01 03 30 00 00 08 4B 0C
I calc the CRC by using some tools,the right CRC shoud be 0C 4B , and i using 0C 4B send the command can get right result. It will get “CRC Error” when i send using 4B 0C.
How can i solve the problem?
Thanks!

[manjey73]

http://modbus.rapidscada.net

Probably your device is not quite standard. If you use the specified link and check your request, the CRC is correct, the lower byte forward, according to the Modbus Protocol.

https://www.lammertbies.nl/comm/info/crc-calculation.html

Online Calc shows just the CRC value as it is.

I would like to look at this device that does not send CRC Modbus younger byte forward, I have never seen this in the factory products.

• This reply was modified 5 years, 10 months ago by manjey73.

[lgr]

Hi,
Thanks for your reply.
It is an analog signal acquisition equipment bought through E-commerce website. https://item.taobao.com/item.htm?id=566584520351
If the problem caused by the device , can i solve the problem by software setting ？

[manjey73]

Write to the Chinese that they have the wrong byte sequence in the CRC. Well, if it does not help, you can try to build KpModbus.dll in the new version, where you change the sequence of bytes for CRC, and to call it KpErrorModbus.dll 🙂

[lgr]

Thanks very much!
I have contacted the vender and confirm the problem.

[manjey73]

01 03 30 00 00 08 4B 0C

So it became clear that any online calculator Modbus CRC in the calculation of CRC along with it should give the result 0

AI 0-20, 4-20 mA

It was necessary to buy such a module, there is a description in English and you can check the information on the Protocol and the method of calculation of channels.

• This reply was modified 5 years, 10 months ago by manjey73.

[lgr]

Yes,
Thanks very much!

[Author]

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