Berechnung Der Checksumme; Beispiel-Code - SIEB & MEYER SD2 Originalbetriebsanleitung

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8.A.3

Berechnung der Checksumme

Beispiel-Code:

// example receive buffer filled with data from communication example 1:
char receiveBuffer[] = { 0x00 0x0d 0x01 0x02 0x90 0x01 0x00 0x31 0x72 0x00 0x00 0x00 0x00 0x00 0x00 0xbb
// this function creates the checksum
unsigned char CheckSumm (
{
unsigned char Summ =
int i;
int length = receiveBuffer[ ];
int lastIndex = length + 2
for ( i = 1 ; i lastIndex ; i < ++
{
Summ += receiveBuffer[i];
}
return ( 0xff - Summ);
}
// this function compares calculated checksum with received checksum from receive buffer
bool CompareCheckSumm(
{
int length = receiveBuffer[ ];
int checksummoffset = length
if ( receiveBuffer[checksummoffset]
return true ;
else
return false ;
}
Antriebssystem SD2 - DNC 8 Byte Telegramm
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char * receiveBuffer)
0 ; // start value for the checksum
// loop counter
1 // amount of bytes to create checksum
; // last valid index for checksum loop
) // loop run from "length" byte to last "data" byte
// add new value to last result
void )
1 // length of checksum data
+ 2 ; // index in the array where the checksum is saved
== CheckSumm( receiveBuffer[ ] ) )
// compare received checksum with calculated checksum
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& 0
Anhang
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8.A