Thinking about this regulator to bring the voltage down to 3.3V: http://www.pololu.co...og/product/2110

I'm sure I am telling a granny how to suck eggs but...that feed will be 0-12-0 (mine is), an connecting that to your Netduino will cook it. You'll need a voltage divider for it to bring it down to a happy level (3.3 or 5)

You are correct. Don't need to let out the magic smoke inside the Netduino.

For frequency counter, use an InterruptPort trigerred by one edge (either InterruptEdgeLow or High) and subtract time passed to OnInterrupt handler and previously stored one, averaged over certain number of samples. I have posted a pulse meter code sample, which measures pulse width, so just replace the interrupt mode to get started.

Precise measurement can be done using Timer Capture mode, which is not currently available on Netduino (Edit: The microprocessor has it, but the necessary pins are not broken out and there is no software support in the firmware).

Yep that's what I needed. The code should make what I want to do very easy. Thanks CW2! I'll just use an InterruptPort event handler to count the number of pulses received every 500 milliseconds, then perform my calculation to determine MPH.

Thinking about tying into the original cluster's English/Metric button and have it switch from MPH to km/h.

Also eventually want to explore using a small motor to retrofit a cable-driven analog cluster to accept a digital VSS signal. So many options to explore!

Does the vehicle have an (accessible) ODBII connector?

No OBDII. Vehicle is OBDI (which would still work using the OBDI connector to retrieve speed).

For frequency counter, use an InterruptPort trigerred by one edge (either InterruptEdgeLow or High) and subtract time passed to OnInterrupt handler and previously stored one, averaged over certain number of samples. I have posted a pulse meter code sample, which measures pulse width, so just replace the interrupt mode to get started.

Precise measurement can be done using Timer Capture mode, which is not currently available on Netduino (Edit: The microprocessor has it, but the necessary pins are not broken out and there is no software support in the firmware).

Definitely going to give this a look. This might be what I'm looking for.

Everything since 1993 ? has an ODBII connector, usually under the dash above the driver's right knee. Monitors general Obd-2 data: Fuel system (open/closed loop status), Engine load, Coolant temperature, Manifold Pressure, Engine Rpm, Vehicle speed, Timing advance, Intake air temperature, Intake air flow rate, Throttle position, Secondary air status.

Google OBDII , and you'll find a gaggle of articles and projects about interfacing.

Everything since 1996 for sure. Some GM vehicles have the bastardized OBD1.5 which is OBDI with an OBDII connector. The test case is a vehicle from 1989, so definitely OBDI. Don't want to use the ALDL to get the information though since the intended use will be to retrofit an existing digital instrument cluster with a more accurate digital speedometer.

Hi folks. Very new to Netduino development and wanted to run a project idea by some of you to see if it's possible, and/or how I'd go about it. My idea is to make a digital speedometer for a vehicle by tapping into the vehicle speed sensor (VSS) feed from the powertrain control module (PCM) to the instrument cluster. The VSS on the transmission sends a digital signal to the PCM. Most applications vary, but the vehicle I'll be working with has a VSS that sends out 4000 pulses per mile. I've already decided on using the display here: http://www.sparkfun....roducts_id=9767 What I'm wondering is how would I go about reading the pulses with the Netduino? Are the PWM pins output only? Or can I hook the VSS feed up to one of the PWM pins and read the number of pulses being sent over the line? Thanks for entertaining my noobish question. Have some other ideas for automotive applications, too. Looking forward to getting started with them.