Megasquirt to Cluster VSS Signal
 

Long story short, I no longer have a Miata trans or VSS in the trans. I have speed in the MS3 for traction control purposes and I'd like to send a signal to my NB cluster to have the needle move again and the cruise control function.

I know:
Speed input to the cluster is AC sine wave on two wires
I can only pulse an output to ground for speed from the MS3
Just hooking an output from the MS3 to one of the wires of the speed input won't work

I don't know:
How to emulate the AC sine wave with just a switched output
If the cluster can accept a square wave DC signal if I use a pull up resistor

Anyone have any insight or suggestions?

Aidan already did it.

https://www.miataturbo.net/ecus-tuni...r-85749/page2/

The VSS outputs a zero-centered sine wave signal that increases in amplitude and frequency as the speed increases.
I'd bet the odometer unit will take a square wave just fine, but you may need to make it cross zero? Depends how it's triggered. For some reason I recall feeding it with a function generator as part of testing my cluster and it worked fine with a 0-12V square wave.
Definitely worth trying with a pull up to switch between 0 and 12V. I used to have some captures of an oscilloscope readout of the waveform but I can't seem to find it right now.

Son of a bitch, my search foo is rusty from hanging out on Facebook too much.

Thank you

// WRONG THREAD
Removed my question I was in the wrong thread, Im sorry!