I just did a little test to make sure the RPM signal was working. My vehicle is running on it's original injection system (L-jetronic). The Megasquirt (MS II, board V3) is all wired up, except it is not connected to the IAT, CLT and injectors. I'm using Tunerstudio to monitor the sensors and everything is working, except for RPM. (RPM does work with stim) MS is connected to the EDIS module which is wired per this scheme:

However, I have disconnected the edis coil, since I'm just testing and running the original dizzy and coil. The MS is jumpered like this:
and D2 is installed, but bridged.V3.0 main board:
* DB37 pin #36 to the SAW pin (#3) on the ignition module
* DB37 pin #24 to the PIP pin (#1) on the ignition module
* On the V3.0 main board:
o use the 'Hall sensor circuit' (step #50.a in the assembly guide) - jumper D1 and D2,
o jumper OPTOIN to TACHSELECT on the bottom side of the PCB, near the DB37 connector, opposite the heat sink,
o jumper TSEL to OPTOUT on the bottom side of the PCB, near the center.
* jumper JS10 to IGN (this uses the processor port for the SAW signal directly),
* jumper XG1 to XG2 on the bottom side of the PCB, near the 40 pin socket,
Couple of questions:
- Does it matter that the EDIS coil is disconnected?
- Do I need to adjust the VR pots on the MS? Or aren't these used when using EDIS?
- If the wires on the VR sensor are the wrong way round, do I get 0 rpm, or something else? (I'm not 100% sure if they are on correctly)