Friday, June 3. 2016
OVMS Nissan Leaf Remote Climate Control
I've added remote climate control support in the Nissan Leaf OVMS firmware. This is relatively straightforward because Nissan built this feature into the Leaf's CARWINGS package. In New Zealand CARWINGS wasn't sold with the Leaf and Japanese import Leaves have a Japanese cell phone which doesn't work in New Zealand. Making it work here means emulating the function of the TCU module. On a Gen 2 Leaf this is simple, send a CAN bus frame to wake the car up and another frame to tell it to turn on or off the climate control, or start charging.
The Gen 1 Leaf is a little more complicated. The TCU wakes up the car by applying 12v to a wire, telling the VCU to wake up. After the VCU wakes up, the TCU sends the same command message as on the Gen 2 car. The OVMS hardware doesn't have an external 12V GPIO so I had to make something. I had a small relay lying around and using that was easier than building a 12v protected output. I glued a drive transistor on one side of the expansion port and the relay to the cell phone module. The LED catches the relay's turn off spike but any diode would do.
I used the previously unconnected Ring Indicate pin on the DIAG serial port to get the 12V signal out of the OVMS. RI is a good pin because it's an output from the OVMS and it is intended to tell the host the phone is ringing which matches up well with the "hey something important is happening, pay attention" use here. RS232 uses +12v signaling so a normal serial device will still be ok to plug into the port. The wire from the relay goes through one of the mounting holes for the serial port to access the pins on the back side of the circuit board, this avoids fouling the case which is pretty tight on all sides of the circuit board.
I've disconnected Nissan's TCU and stuffed a wire into it's plug to connect the OVMS to the Leaf's wiring loom. Nothing has complained about the disconnected TCU that I can see.
I'll post a schematic shortly.
Remote climate control is great, you can press a button on the OVMS cell phone app to get the car headed to toasty warm or cooled down before you get to it. If it's not plugged in then you get 15 minutes of cooling or heating, and more if it is plugged in. You can't control what the climate control does, Nissan have hard coded it to target 25C which is likely to cool the cabin in the summer and certainly heats it in the winter. Nissan have programmed the remote climate control to use recirculated air so in winter the windows are usually fogged up. I don't think there is anything I can do about that but the windscreen button once you're in the car doesn't take long to clear it.