Smart-E Matrix Checksum

mshunt

Hello all,

I've been trying to control a Smart-E 8x8 matrix, the protocol is pretty straightforward, but it requires an XOR checksum on all the previous bytes appended to the end of the string. I could calculate the checksum manually, but that means a huge library of statements to cater for all the different permetations of the matrix.

The code i'm trying to use is

DEFINE_FUNCTION sendswitcherstring(CHAR cmd[50])
{
switcherstring="$BE,$EF,cmd"
checksum=left_string(switcherstring,1)
for(x=2;x<=length_string(switcherstring);x++)
    {
    tempstring=mid_string(switcherstring,x,1)
    checksum=checksum BXOR tempstring
    }    

send_string dvSwitcher,"switcherstring,checksum"
}

It works in my head, but it's obviously not working in practice as it never gets the right result.

Any ideas?

AMXJeff

mshunt wrote: »

Any ideas?

This seems to work...

DEFINE_FUNCTION CHAR Calc_Checksum(CHAR cData[])
{
	STACK_VAR CHAR CS;
	STACK_VAR BYTE;
	
	FOR (BYTE = 1; BYTE <= LENGTH_ARRAY(cData); BYTE++)
	{
		CS = CS BXOR cData[byte];
	}
	
	RETURN CS;
}

DEFINE_PROGRAM

WAIT 100 
{
	LOCAL_VAR CHAR cData[100];
	
	cData = "$BE,$EF,$00,$00,$00,$00,$00"
	
	SEND_STRING dvDevice,"cData, Calc_Checksum(cData)";
}

mshunt

I got it working, I was trying to use a CHAR as the checksum variable, and it just wasn't working. When I set checksum as an Integer it worked, Netlinx compiler did the rest. I've had to use the same method for PTZ camera control and I got that working today.

I'm still getting my head around different variable types.