My 2 bobs worth for the speedo project.

Start a 1mS timer.
On 1st pulse from wheel, reset counter.
On 1mS timeout increment the counter. This will need to be 2 byte.
On 2nd and subsequent pulses from wheel, temp store count data and reset
counters.

The integer result of 1CD4h divided by the count value will give you the
current KM/H.

Convert this to 3 digit BCD and display it.

Wait for next wheel pulse and continue.

Allowing for wheel wear and tyre inflation etc., I think the integer
maths will be accurate enough.

At 1 KPH the count value will be 1CCEh.
At 160 KPH the count value will be 002Eh.

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Best regards

Tony

Multimedia 16F84 Beginners PIC Tools.

http://www.picnpoke.com
Email picnpoke@cdi.com.au