Communicating with the Lexus GS450h Inverter/Converter

[catphish]

Would still be interested in seeing captured waveforms though.

Thanks, I will try to capture the raw waveforms from Jackk's GS450H post them here to confirm.

[Pete9008]

It would be good if you could.

The difference is best seen when looking at the differential signal between the two conductors. If it's unipolar (returns to zero) then it's CAN, if it's bipolar then it's RS422/485.

Edit - that's assuming that they haven't added extra non standard pull ups/downs at either end!

[catphish]

Damien did a differential measurement (attached). Looks like it's 2V differential and returns to zero, which seems awful, but if that's what it is and it works, great! I would prefer to see the individual signals with reference to GND to confirm, so will do my own measurements too. It does seem like it might be CAN though.

[xp677]

I based my assumption on the IC pinout and the logic levels as well. Could easily be another type of transceiver.

The fact that CAN transceivers at the other end seem to work perfectly to communicate with this unit is another thing in favour of the theory that it's CAN transceivers in there.

[hazelnut]

Coincidentally I've been looking at this today. Here is a picture of what Lexus calls the Hybrid ECU from a 2009 Lexus GS450h. This unit talks to the inverter using 4 CAN-like interfaces.

I've buzzed out the CAN connections using the lexus wiring diagrams. From left to right there are 6 CAN modules: HTM, MTH, CLK, REQ, Gateway and ABS. The interface chips are 4 Denso Se787 and 2 Denso Se617 respectively. I could not find a manual for the Denso parts, nor what the difference is between the Se787 and Se617. However the pin out appears to be the same SOIC-8 configuration of a number of CAN chips including the MCP2561 and NXP TJA1042. My plan is to fit the Zombiverter circuit onto a PCB that fits directly into this ECU box using the original ECU connector, and thereby allowing a direct swap into a GS450h allowing the engine to be removed. Next up I need to reverse engineer the accelerator.