In case it may be useful for anyone I'll post my experience before I forget what I went through.

I removed the EC3 from the plane, hooked it up to Mode, Cold-start, A/B and Store switches and a 12V battery.

You'll need an 2-channel oscilloscope and a timing wheel simulator for the CAD input. I borrowed an Arduino Nano with downloaded Ardu-Stim software, compiled and uploaded to the Nano. Output on PORT8: pin D8. (Tried to upload to an Arduino MEGA 2560, output probably on one of pins 50 to 52, signal not as sharp.)

https://gitlab.com/libreems-suite/ardu-stim

Open it with arduino.exe". There you'll also need to install (Tools | Manage Libraries) SerialUI (version 2.2.0) before you can compile and upload the sketch to the Nano.

In order to interact with the Ardu-Stim on the Nano, you need to download, install and run Druid4Arduino.exe

https://sourceforge.net/projects/druid4arduino/files/druid4arduino-1.3.1/

Now that you have the Nano powered by your laptop and Druid4Arduino.exe running and the Ardu-Stim menu showing, the trick is to pick the right timing wheel. Wheels 16, 17 and 36 give vastly different results (and any of them may actually not be the right one for the Renesis -- I still need to compare my timing wheel to the pulse output to my timing wheel -- I'll be looking at?? this:
https://www.maxxecu.com/webhelp/trigger_system-mazda_rx8.html)

Trigger the scope on one of the coil outputs on the J1 connector (pin 11, 10, 14 or 15) and have the other channel show the CAS input (J2 pin 5).

The coil pulse should be positive and no wider than the dwell time specified for the coils you programmed the EC3 for (4.3 ms for LS1 coils, 4 ms for LS2 coils). As far as I know, coils will fire on the negative edge on the pulse (coil charges while pulse is positive -- dwell time -- and fires when pulse disappears). So that's what you'll want to compare to the wheel timing pulses on the other channel.

The sweep option in the Ardu-Stim is very useful. For example, sweep from 100 to 6000 RPM at 100 PRM/Sec. I found that just because it looks good at 6000 RPM it doesn't mean it works at other RPMs.

I'll keep you posted on what I find.

Finn

P.S. I guess another way to get a realistic test CAS input would be to remove the timing wheel and sensor, mount them in a jig and power it with a variable speed motor. In that way you can verify the input (and clamping circuit) too.