[OT] CAN transceiver

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

Colleagues,

I have never used CAN, and I'm designing a board whith a working name "CAN playground". It will have a couple of PIC18F258s and a bunch of different CAN peripherals. Rolling my own board is more fun then buying one from CCS. The question is: what CAN transceiver to use? In this forum I have seen people use MCP2551, PCA82C250, LT1796. These transceivers seem to be pin-for-pin compatible. Is there any preference?

Thanks!
~K

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

The CCS CAN bus drivers configure the PIC to use a transceiver that
has an internal pullup on the microcontroller side of the transmitter.
Not all transceivers have this internal pullup. This can cause quite a
mess until you figure it out. See this thread. It is finally resolved
on page 2.
http://www.ccsinfo.com/forum/viewtopic.php?t=23825

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

I see. So, I can use any transmitter, as long as I leave pads for an external pull-up resistor, can't I?

newguy · Joined: 24 Jun 2004 Posts: 1903

Actually, I'm still waiting to hear back from CCS regarding that issue. I'm very sure that the CAN_DRIVE_HIGH (or whatever that define is called) should be a 1, not a 0 as in the driver files. I keep checking the new releases of the compiler, but it's still defined as a 0.