CODEWITHSUNDEEP
c#checksum
Rikin Patel
Rikin Patel

Reputation: 9383

Calculate checksum for Laboratory Information System (LIS) frames

I'm developing an instrument driver for a Laboratory Information System. I want to know how to calculate the checksum of a frame.

Explanation of the checksum algorithm:

  1. Expressed by characters [0-9] and [A-F].

  2. Characters beginning from the character after [STX] and until [ETB] or [ETX] (including [ETB] or [ETX]) are added in binary.

  3. The 2-digit numbers, which represent the least significant 8 bits in hexadecimal code, are converted to ASCII characters [0-9] and [A-F].

  4. The most significant digit is stored in CHK1 and the least significant digit in CHK2.

I am not getting the 3rd and 4th points above.

This is a sample frame:

<STX>2Q|1|2^1||||20011001153000<CR><ETX><CHK1><CHK2><CR><LF>

What is the value of CHK1 and CHK2? How do I implement the given algorithm in C#?

Upvotes: 15

Views: 45478

Answers (3)

Aleksey
Aleksey

Reputation: 320

You can do this in one line:

return Encoding.ASCII.GetBytes(dataToCalculate).Aggregate((r, n) => r += n).ToString("X2");

Upvotes: 1

Barak Rosenfeld
Barak Rosenfeld

Reputation: 337

private bool CheckChecksum(string data)
{
   bool isValid =false

   byte[] byteToCalculate = Encoding.ASCII.GetBytes(dataToCalculate);
   int checkSum = 0;
   for ( int i=i i<byteToCalculate.Length;i++)
   {
      checkSum += byteToCalculate[i];
   }
   checksum &= 0xff;

  if (checksum == byteToCalculate[ChecksumPlace]
  {
   return true
  }
  else
  {
  return  false
  }
}

Upvotes: -4

Rikin Patel
Rikin Patel

Reputation: 9383

Finally I got answer, here is the code for calculating checksum:

private string CalculateChecksum(string dataToCalculate)
{
    byte[] byteToCalculate = Encoding.ASCII.GetBytes(dataToCalculate);
    int checksum = 0;
    foreach (byte chData in byteToCalculate)
    {
        checksum += chData;
    }
    checksum &= 0xff;
    return checksum.ToString("X2");
}

Upvotes: 19

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