Originally Posted by Saml01
Am I confused, or did I read somewhere that you can buy a daughter board that coverts an MS1 to an MS2?
Well, the MS2 CPU itself is technically a daughterboard. Whereas the MS1 CPU is just a big ole' 40 pin DIP, the MS2 CPU is a tiny little surface-mount devices, and it's packaged onto a daughterboard which adapts it to fit the 40 pin DIP socket, along with a stepper IAC controller and a few other little things.
There's some info at the MS2-Extra site
about upgrading from MS1 to MS2.
In short, you remove the MS1 CPU, install a jumper on the bottom of the board to bring +12 to pad JS9 (the IAC controller needs +12, even if you aren't using it) and then install the MS2 daughterboard into the CPU socket.
A couple of the pin designations change between MS1 and MS2, so you'll likely need to change a couple of your internal mods. Additionally, if you plan to use the NB stock crank & cam sensors, it'd be advisable to remove your current CAS input mods and build the newer versions described by Abe & Jason. The old ones "should" work, but the NB sensors tend to be more finicky than the CAS.
Where can I read more about active falling/rising triggers? I have no idea what that means.
Ok, here's a quick tutorial. Below is a scope capture I took of the two signals coming out of the CAS. The NB sensor signals are sufficiently similar (in terms of their electrical characteristics) that this will suffice for both:
The upper, green trace is CKP, and the yellow trace is CMP. These signals are shown as measured at the CAS output, assuming externally pullup.
The rising edge is where the voltage goes from 0v to 5v, seen here as the upwards or rising slope (the left side of each plateau). In this case, the leading edge is the rising edge.
The falling edge is the transition from 5v back down to 0, which the trailing edge here.
Rising vs. falling, leading vs. trailing. The former describes the absolute electrical polarity, whereas the latter describes the logical orientation of the signals. If we inverted these traces, then the leading edge would be a falling edge.
OK, now because of the physical design of the MS1, the CPU's hardware interrupt pin is used as the primary trigger. This pin can only "see" falling edges. IOW, the CPU does not notice when the voltage on that pin goes from 0 to 5, only when it goes from 5 to 0.
To complicate matters, the circuits on the MS board can be either inverting or non-inverting. IOW, they can pass along the signal to the CPU exactly as you see it here, or they can flip it over so that 5 becomes 0 and 0 becomes 5. In the usual Miata layout, we wire the CKP input so that the circuit is inverting, and the CMP input so that the circuit is non-inverting.
On MS2, you typically wire both circuits the same, because the CPU is capable of dealing with rising edges or
falling edges on both inputs.
As long as I dont have to make another boomslang, I will be up for anything. That was easily the most PITA of the whole project.
Yeah, this is part of my loathing for parallel builds. Too damn much wiring.
You will be able to keep your boomslang as-is. Remember, pretty much every pin on the DB37 that isn't hard-wired to a specific function just goes to a general purpose pad, and from there to your I/O mods. So you have full control inside the unit as to what signal uses what pin. Just make sure that your internal mods, where appropriate, are re-wired to the correct CPU pin, and you're golden.