Calculate checksum for Laboratory Information System (LIS) frames

c# checksum

45,100

Solution 1

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");
}

Solution 2

You can do this in one line:

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

45,100

Author by

Rikin Patel

Updated on July 20, 2020

Comments

Rikin Patel almost 4 years
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#?
- Rikin Patel almost 12 years
  
  i m confusion in what is final ans. it is 4 digit or 2 digit.and i am not getting what i will do after sum of all byte.
- Rikin Patel almost 12 years
  
  this is sample frame : <STX>2Q|1|2^1||||20011001153000<CR><ETX><CHK1><CHK2><CR><LF> and i want to know what is value of chk1 and chk2 and i am new in this so i m totally blank about how to calculate checksum.
- Collin almost 12 years
  
  Like we talked about in chat, we need to know what kind of checksum algorithm the instrument is expecting you to use. Is it a CRC, Fletcher, or something else?
- Rikin Patel almost 12 years
  
  @Collin this things does not disclose in documentation of instrument just given above explanation.
- janw almost 4 years
  
  Note: This question has also been posted on Software Engineering SE. I have edited this question to include some context.
Rikin Patel almost 7 years

Pls, read Que. I want checksum value of given string but your ans. returning the boolean value.
Rikin Patel over 4 years

you are missing "checksum &= 0xff"
Aleksey over 4 years

No, this is not needed as the type of r is byte, it can't go over two letters
PauLEffect over 4 years

Let's assume that byte[3] = {0,0,0} gets sent instead of your actual buffer. The checksum is 0, and it's valid... you ought to check for that case, among other things. It's a really weak checksum algorithm (no offense).