About the reset, I did see a reset pin. But what does the other side of the switch connect to? Ground?
Heres a pic of what Ive done. I put the switches and components on a thin strip of circuit board that fits down from the display. So the display and buttons up top, and Freeduino on the back. It will be mounted in a plastic case when done.
I wired it into the car tonight. It gives back information, but all wacky. Speed says about 16 mph, when idling in park. Kind of jumps around when driving. I wonder what is supposed to be coming off the VSS wire. Mine works by sending power back to the ECM, so I am picking up pulses on the ground side. Do I need to pick up positive power pulses somehow?
One thing I am thinking may be wrong is that I tapped into the cruise control module because it was easier to get to. It uses the same 4000 pulses/mile as the speedo, but since the cruise is not turned on, it is probably not sending power and making pulses and might be picking up stray signals instead. Since I dont have a working cruise stick right now, I should find my old wire and bridge 2 wires so it is on all the time, then try that.
My injectors work by 2 banks of 3 injectors firing at a time, each grounding through a separate switch in the ECM. So I tapped into one of the wires on the ground side of the injectors. Then I doubled the microseconds/gal value in the guino since I am technically getting only half the fuel pulses. Online sources
http://www.nitrostreet.com/injectors.htm say my injectors are 15 lb/hr, so I based that on fuel at 6 lb/gal and did the math for 3 firing at once. Ended up with 480,000,000 microseconds/gal.
My mpg says 99.9 all the time, which does not make sense even if the speed was off by the amount on the display. So something must be fishy.
Also the screen never went garbled or anything. However, every time I would shut off the engine, the buttons would no longer function. But after restarting the car and the unit getting data, they would work again. Unless I either hit reset, or unplugged the power for a second, then they would work again.
Also, I understand the screen is supposed to time out after 7 minutes? Mine never turned off even after like 20 minutes, so I unplugged it and brought it in the house for the night. I havent actually done the math on the default variable though, I figured it would be right.