Melssj5:
Its a 1979 car, the speedometer is driven by a rotating cable, So I must buy a device to transform that as pulses. 16 pulses per rotation..... But the question is, the faster the car moves, the faster the pulses will come. How can I be sure that I wont loss signals while reading ..... the pulse generator has its frecuency depending on the speed car, and the arduino loops in whoknows frecuency. What it pulses are generted faster than arduinos loop frecuency.Another question, I guess Arduinos cannot support multihtreading, so how can I know the speed If I cannot have a separate thread to count the pulses and compare then in a time lapse...???? Should I only receive and publish the data gathered from the cluster and do the maths, interpretation, comparissons, etc etc etc on the Android app to ensurace a light running script on my arduino?
Arduino works great doing cooperative multitasking, depending on the frequency tasks need to run as void loop() can run in excess of 100KHz but it won't be doing much in any one pass but check a pin and increment count or like.
Consider that loop() can be made to run 50+ times per millisecond and do some useful things at the same rate, which adds up quick.
So how many times per second does it pulse at 60mph or 100kph (almost 62mph)?
At 16 pulses per wheel rotation, how many rotations per second at top speed can tell you how fast you have to keep track of pulses. I suspect that the pulses will be magnitudes slower than the code.
With a 15" rim, a 27" dia tire is typical, moves almost 85" per rev, 747 revs per mile x 16 pp-rev gets into 12000 pulses per mile.
Lets say the car goes 120mph, that is 12000 pulses in 30 seconds, 400 pulses per second is 2.5 ms per pulse. Arduino could watch that ooze by, only if the code lets it. Code that blocks execution (use of delay) does not let it in general.
I have code that reads serial chars and tries to match them against a tabled list of words as the chars arrive. The speed test example reads serial and prints trace data to show the match process working. It keeps up with 250000 baud serial, 25 chars per milli, that's chars arriving every 40 micros (640 cpu cycles) with serial output being the heavier cpu load. Yeah, I think you can keep up with 16 pulses per rev even on a 60's Mini Couper at a reduced clock rate to boot.