CRC16 implementation?

[vsurducan]

Hi Rob,

Is there any CRC16 implementation example? DS18B20 library has a CRC8 implemented, but only for bit checking.

I need a CRC16 computation for reading a  MODBUS slave. The polynomial generator is X16+X12+X2+1 and the value for computation 0xA0001.

The C implementation for CRC16 MODBUS seems to be this one:

https://www.modbustools.com/modbus_crc16.html

and an application library here:

https://github.com/mandulaj/PZEM-004T-v30/blob/master/src/PZEM004Tv30.cpp

The problem is that translating this C to jal seems very painful...

I can find each CRC value for each needed command by running a MODBUS software, but the CRC values will be different for each slave address and/or numbers of bytes to be read from one particular slave...which is inconvenient.

thank you,

Vasile

[Rob CJ]

Hi Vasile,

In the virtual_wire library I do the following CRC calculation. A bit different from yours.

-- Calculate new crc over given data. Formula is:

-- Xexp16 + Xexp12 + Xexp5 + 1

function _vw_calc_crc(word in crc, byte in data) return word is

var word data_2

  data = data ^ byte(crc & 0x00ff)

  data = data ^ (data << 4)

  data_2 = word(data)

  return (((data_2 << 8) | (crc >> 8)) ^ (data_2 >> 4) ^ (data_2 << 3))

end function

Kind regards,

Rob

---

Van: jal...@googlegroups.com <jal...@googlegroups.com> namens vsurducan <vsur...@gmail.com>
Verzonden: dinsdag 6 augustus 2024 11:37
Aan: jal...@googlegroups.com <jal...@googlegroups.com>
Onderwerp: [jallib] CRC16 implementation?

 

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[vsurducan]

Thank you, this is helpful. It would be even better if would be commented... :). 

To view this discussion on the web visit https://groups.google.com/d/msgid/jallib/GVXP195MB1637A05519FEAED5F5BE8E94E6BF2%40GVXP195MB1637.EURP195.PROD.OUTLOOK.COM.