HI-TECH Software Forums: J1939 Microchip C Library (modified)

First thanks for the Post.
The library does work, pretty good stuff

It saved me some time, so here is what I learned:

Here are some problems I found (with the base code not the translation) Most have to do with arbitray address arbitration.
Bug / Issue
1. in J1939.def
#define J1939_ARBITRARY_ADDRESS 0x80 // 0x80 = Yes, 0 = No

2.in J1939.C
If you chip is not in the defines, the code may not set the CAN port pin direction.

3.in J1939.C
void J1939_Poll( unsigned long ElapsedTime )
The elapsed time says ms (millisec) but it is microsec
the constant should be 2500000L (2.5 seconds)

Note that I got 20uSec @ 8Mhz not the 5mSec in the example

4. in J1939.C
signed char CompareName( unsigned char *OtherName )
the bytes are compared in the wrong order. ( I found this "Common" mistake reported elsewhere).

Try:

Code:


signed char CompareName( unsigned char *OtherName )
{
	unsigned char	i;

	// BUG In Origional Sample Compare is the wrong way
	//for (i = 0; (i<J1939_DATA_LENGTH) && (OtherName[i] == CA_Name[i]); i++);

	// Byte 0 is LSB
	i = J1939_DATA_LENGTH;
	do
	{
		i--;
	}
	while((i != 0xFF) && (OtherName[i] == CA_Name[i]) );


	if (i == 0xFF)
		return 0;		// Must be equal
	else if (CA_Name[i] < OtherName[i] )
		return -1;
	else
		return 1;
}

or code your own.

I did not get the CAN Interupt to work. The code confused the compiler. Some of the code gets call before before the Interupt is enabled. The compiler saw function called from main and the interupt. I stuck with polling for now. Code:

SendAddressClaim:
// Send Address Claim message for CommandedAddress
CopyName();
OneMessage.Msg.SourceAddress = CommandedAddress;
SET_NETWORK_WINDOW_BITS;

SendOneMessage( (J1939_MESSAGE *) &OneMessage );

if (((CommandedAddress & 0x80) == 0) || // Addresses 0-127
((CommandedAddress & 0xF8) == 0xF8)) // Addresses 248-253 (254,255 illegal)
{
J1939_Flags.Flags.CannotClaimAddress = 0;
J1939_Address = CommandedAddress;

// Set up filter to receive messages sent to this address
SetAddressFilter( J1939_Address );
}
else
{
// We don't have a proprietary address, so we need to wait.
J1939_Address = CommandedAddress; // ADDED NSK, need this here so we know the last failed address
// if we do several address claims to find an address
J1939_Flags.Flags.WaitingForAddressClaimContention = 1;
ContentionWaitTime = 0;
}
}



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