Single wire CAN // Saab 9-3 I-Bus // GMLAN
Most small microcontrollers (like those used on the Arduino) won't be fast enough to implement CAN in software. That's why the CAN Shield uses the MCP2515 CAN controller IC. 

I recommend one of two options:


Connect an MCP2515 chip to your Arduino, and use the AU5790 CAN transceiver. Either do this on a breadboard or design a PCB.
Use the Arduino CAN shield, but solder some jumper wires from the TXD, RXD, and GND lines over to another board with an AU5790 on it.
Download the schematic and PCB designs for the Arduino CAN shield, and adjust the design to accept the AU5790 instead of the MCP2551.


Unfortunately, the AU5790 doesn't seem to be pin-compatible with the MCP2551. It nearly is, which is a shame.