CANbus / UL Power Integration

Finally got around to wiring the Dynon EMS-221 to the UL ECU.

The Dynon manual does not give a lot of detail, except the pinouts - and there are omissions.

Here is what came with the engine and harness:

On the EMS side, the manual gives some info on UL Power installations, but it is not overly helpful.  However, I asked Advanced specific questions about the ground wire, 120 ohm resistor, and shield from the UL side.  Below is what I got back.

This is what I followed.  I added the termination resistor (however, Advanced noted that they probably have many Rotax installs in the field with no resistor, and no issues), ground, and tied the shield to the EMS ground.

When I fired everything up, there was no obvious was to see the CAN bus status.  I poked around forever and nothing was obvious.  I had a 2AM brainwave that I needed to change the engine selection.  My PFD was set to '6 cylinder turbo', when it should have been 'UL 6 cylinder turbo'.  As soon as I changed that, I now had the option to select CANbus inputs for the different gauges and I could see that CANbus was connected and working.

As you can see, there is an OIL PRESSURE A and OIL PRESSURE B - where A is valid, and B is not.  I assume B is for if you have a 2nd ECU.  Confirmed on 12/6/2022 that the 'B' lane is for a 2nd ECU..

Everything appears to be working.  I have to set the limits on everything still, but that can wait until closer to first engine start.

Dynon EMS-221 Wiring

As Advanced Flight Systems is part of Dynon, it stands to reason that Advanced would use the Dynon EMS (Engine Monitoring System) unit.  Dynon has 2 flavors - the EMS 220, which is the standard unit - and the EMS 221, which has CAN-bus connectivity.  I need the 221.

The EMS-221 has 3 connectors:

1. DB9 for the Skyview Network connection
2. DB37 for all of the engine wiring (except CHT and EGT)
3. DB25 for CHT and EGT probes

1 and 3 are straightforward.  2 is interesting.

The UL ECU passes most of the engine data over the CAN-bus connection.  From the UL manual...

Bottom line:  There is very little for the EMS-221 to do, other than getting the CAN-bus data from the ECU.  Here is the pinout (only yellow items are planned to be used)

Basically current, voltage, fuel tanks, and CAN-bus.  I have a question into Advanced on whether or not I can use the 2 voltage pins, as these are on the ACM as well - so these might not be needed).

Everything is wired, except for the tank sensors.  Kinda need the wings for those...

I put the EMS on the bottom of the right hand avionics tray, thinking this would be easy to get to. Yeah, right.  Its not impossible, but definitely not easy.  Removing the ECU makes it easier.