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so I've never worked with arduino before, but i do have some basic programing knowledge (c,vb)

i ordered a UNO and a lcd in the hopes of building a display to output engine rpm, throttle position %, fuel %, and engine temperature.

ive worked out alot of the logistics already, but im not sure where to start with the code. i know that the rpm is a square wave,12v signal, throttle position is a .5v to 4.5v output, fuel % is 2ohm to 110ohm output, as for the engine temp, i am going to be adding a thermistor to the coolant system.

i know that the throttle, temp and fuel are going to be analog inputs, and the rpm will be digital (correct me if im wrong)

i know that i will have to step down the 12v to 5v.

i just need to be put in the right direction as far as coding this.

thanks in advance
gabe
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Sounds like you are on the right track.  RPM is most easily read with an interrupt.  When the interrupt is triggered, subtract the current time from the previous interrupt's time stamp and then do a little math to convert to RPM.  Sometime like:

60,000,000/(time1-time0)=RPM

Analog inputs are easy.  You have a 0-5V signal that the ADC translates as 0-1023.  For throttle for example, just map 0-1023 to 0-100 (%) and print the results to the LCD screen.
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Check out these topics:

http://arduino.cc/en/Reference/Map

http://arduino.cc/playground/Main/ReadingRPM

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thanks digger. i read through everything and i just had a question. it looks like i have to set the high and low limit, and everything in between. is that correct?
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nevermind. all my inputs are linear
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You can read a lot of stuff from OBD Diagnostics in your vehicle.
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i wish i could, but my car is OBD0 so there's no way to directly communicate with it.
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