Great site!
I've been tinkering with a data acquisition system for my 1967 Mustang. All the newer vehicles can tie right into their OBD to pull data like RPM, air-fuel ratio, exhaust gas temp, etc. But older cars like mine don't have such luxuries.
It so happens that my car has an MSD-6AL ignition module that has a tachometer port. It outputs a 12V (20% duty cycle) square wave. I figured this would be a good place to start collecting data.
I figured a linux laptop with the "parapin" driver from sourceforge.net would let me write and read to/from the printer port. First I wanted to take the "pulses" from the MSD directly to pin-10 and calculate RPM via a processor interrupt. Now, I think using a binary ripple counter works better, and I've added some other functionality, like reading 1-5V signals from O2 sensors, etc.
I've got about 90% of the C coding done, I just need some help with the circuit design. I was a CS major in college. I did have classes in digital/analog circuits...but that was a LONG time ago and I'm more than rusty. Would someone be willing to have a look at what I've done so far? Comments/suggestions/*ANY* help would be appreciated!
Thanks!
Doug Eckert
Pennington, NJ
I've been tinkering with a data acquisition system for my 1967 Mustang. All the newer vehicles can tie right into their OBD to pull data like RPM, air-fuel ratio, exhaust gas temp, etc. But older cars like mine don't have such luxuries.
It so happens that my car has an MSD-6AL ignition module that has a tachometer port. It outputs a 12V (20% duty cycle) square wave. I figured this would be a good place to start collecting data.
I figured a linux laptop with the "parapin" driver from sourceforge.net would let me write and read to/from the printer port. First I wanted to take the "pulses" from the MSD directly to pin-10 and calculate RPM via a processor interrupt. Now, I think using a binary ripple counter works better, and I've added some other functionality, like reading 1-5V signals from O2 sensors, etc.
I've got about 90% of the C coding done, I just need some help with the circuit design. I was a CS major in college. I did have classes in digital/analog circuits...but that was a LONG time ago and I'm more than rusty. Would someone be willing to have a look at what I've done so far? Comments/suggestions/*ANY* help would be appreciated!
Thanks!
Doug Eckert
Pennington, NJ
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