Dynalite Checksum Formula

John Paul

I have a Dynalite device for which the commands require a checksum and i wanted to write a function call which will do the checksum calculation for me. I know there are modules available but i wanted to add a simple include file instead. Here is the function i have written, which is incomplete.

DEFINE_FUNCTION INTEGER CKS(INTEGER P1,INTEGER P2,INTEGER P3,INTEGER P4,INTEGER P5,INTEGER P6,INTEGER P7)
{
LOCAL_VAR INTEGER nCheckSum

nCheckSum = !(P1+P2+P3+P4+P5+P6+P7) +1


RETURN nCheckSum

}


Here is the formula for the checksum.

1) In Windows, Start / Programs / Accessories / Calculator

2) In Calculator, under View, Select Scientific

3) In Calculator, select Hex

4) Add the first 7 Hex bytes, then press = (ie: 1C + 01 + 20 + 00 + 00 + 00 + FF total = 13C)

5) Press the <Not> button (in our example, the total = FFFFFEC3)

6) Add 1 to the total (in our example, the total = FFFFFEC4)

7) The checksum is the two least significant characters (in our example, checksum = C4)

George Krietsepis

John Paul wrote: »

I have a Dynalite device for which the commands require a checksum and i wanted to write a function call which will do the checksum calculation for me. I know there are modules available but i wanted to add a simple include file instead. Here is the function i have written, which is incomplete.

DEFINE_FUNCTION INTEGER CKS(INTEGER P1,INTEGER P2,INTEGER P3,INTEGER P4,INTEGER P5,INTEGER P6,INTEGER P7)
{
LOCAL_VAR INTEGER nCheckSum

nCheckSum = !(P1+P2+P3+P4+P5+P6+P7) +1


RETURN nCheckSum

}


Here is the formula for the checksum.

1) In Windows, Start / Programs / Accessories / Calculator

2) In Calculator, under View, Select Scientific

3) In Calculator, select Hex

4) Add the first 7 Hex bytes, then press = (ie: 1C + 01 + 20 + 00 + 00 + 00 + FF total = 13C)

5) Press the <Not> button (in our example, the total = FFFFFEC3)

6) Add 1 to the total (in our example, the total = FFFFFEC4)

7) The checksum is the two least significant characters (in our example, checksum = C4)

John, try the below code:

DEFINE_VARIABLE

volatile CONTROL_MESSAGE[8]


DEFINE_CALL 'CheckSum Calculator' (CHAR BYTE_1,CHAR BYTE_2,CHAR BYTE_3,CHAR BYTE_4,CHAR,BYTE_5,CHAR BYTE_6,CHAR BYTE_7)

LOCAL_VAR
CHAR COUNT
CHAR TOTAL
CHAR CHECKSUM
{
CONTROL_MESSAGE[1] = BYTE_1
CONTROL_MESSAGE[2] = BYTE_2
CONTROL_MESSAGE[3] = BYTE_3
CONTROL_MESSAGE[4] = BYTE_4
CONTROL_MESSAGE[5] = BYTE_5
CONTROL_MESSAGE[6] = BYTE_6
CONTROL_MESSAGE[7] = BYTE_7
COUNT = 1
TOTAL = 0
WHILE (COUNT <8)
{
TOTAL = TOTAL+CONTROL_MESSAGE[COUNT]
COUNT = COUNT+1
}
CHECKSUM = (TOTAL * $FF) BAND $FF
CONTROL_MESSAGE[8] = CHECKSUM
SET_LENGTH_STRING(CONTROL_MESSAGE,8)
}

George

ericmedley

The 'NOT' function in Netlinx is BNOT,

! Is a comparison. BNOT is a calculation.

vining

I needed this calculation a couple of weeks ago so here's the function I came up with and a snippet of code that uses it.

DEFINE_FUNCTION CHAR fn2CompChkSum(INTEGER iStartByte,INTEGER iEndByte,CHAR iStr[])
	
     {
     STACK_VAR INTEGER i;
     STACK_VAR CHAR cChkSum;
     
     if(!iStartByte) iStartByte = 1;
     if(!iEndByte) iEndByte = LENGTH_STRING(iStr);
     for(i = iStartByte ; i <= iEndByte ; i++)
	  {
	  cChkSum = cChkSum + iStr[i];
	  }
     cChkSum = ((BNOT cChkSum)+1);// & $FF);// & FF not needed since return is a single char
     //fnDev_DeBug("'2CompChkSum-[ ',cChkSum,' ] :DEBUG<',ITOA(__LINE__),'>'");
         
     RETURN cChkSum;
     }
     
DEFINE_FUNCTION CHAR fnTV_ProcessQ() 
     
     {
     STACK_VAR INTEGER nFBS;
     
     nFBS = find_string(cTV_TxQueue,"TV_QUEUE_DELIM",1);
     if(nFBS)
	  {
	  STACK_VAR CHAR cQcmd[6];
	  
	  cQcmd = "SAM_CMD_PREFIX,GET_BUFFER_STRING(cTV_TxQueue,nFBS-1)";
	  REMOVE_STRING(cTV_TxQueue,"TV_QUEUE_DELIM",1);
	  
	  cTV_LastCmd = "cQcmd,fn2CompChkSum(0,0,cQcmd)";
	  SEND_STRING dvTV,cTV_LastCmd;

The function allows you to pass it the start byte and end byte of the string to calculate or pass the function 0,0, and it will start at 1 and use the length of the string passed as the byte count.

champ

You really should just use the AMX module as it is really good and quick to implement.

John Paul

Thanks a lot for all the inputs.

Jubal

champ wrote: »

You really should just use the AMX module as it is really good and quick to implement.

where can i get the checksum module?

vining

Jubal wrote: »

where can i get the checksum module?

I think champ was referring to the Dynalite module not a checksum module since there is no checksum module that I am aware of. If you need a checksum function you might try posting your devices checksum requirements and maybe someone will help. This is now a ghost town of a forum so good luck with that.