I might be inclined to use the pru for this and just setup the pru as escentially a hardware counter. There are likely ways to do so with timers and interrupts and such but being more of a hardware guy than software I'm inclined to use a more hardware approach and use the pru as a counter that gets read every so often. the software for that then is escentially a driver that creates /dev/rpm.
Eric On Sun, Apr 6, 2014 at 3:43 PM, Stacy Cottles <[email protected]> wrote: > Thanks Eric for the suggestion. I'll have to figure out the inductive > circuit to use. Do I have to use interrupts or is there something better > for capturing the signal from the pickup? > > > On Sunday, April 6, 2014 1:51:07 PM UTC-5, Eric wrote: > >> an inductive pickup around the sparkplug wire should get you a nice pulse >> each time the spark plug fires but remember the phases of a 4 stroke engine >> (intake - piston down intake valve open, compression - piston up valves >> closed, power - piston down valves closed, exhaust - piston up exhaust >> valve open). The spark plug only fires every other revolution. Once you >> have the pulse from the inductive pickup it should be buffered to provide a >> nice square wave pulse of uniform voltage such that it's easy for the >> processor to use and not a potential hazard to the processor due to >> spurious high voltages (cooking the buffer circuit while in development, >> sorta ok.... cooking the processor, well not so much!) >> . from there it's just software and the incrementing of a counter with >> each pulse. >> >> >> >> >> On Sun, Apr 6, 2014 at 6:33 AM, Stacy Cottles <[email protected]> wrote: >> >>> I am building a web-controlled lawn-mower. I would like to be able to >>> read the RPM off the gas-engine. I would prefer to piggy-back off of the >>> spark-plug if possible since it fires faster as the engine spins faster. >>> Just started on this but would love suggestions. I have a Beaglebone Black >>> running Angstrom and I am using NodeJS to control GPIOs. >>> >>> -- >>> For more options, visit http://beagleboard.org/discuss >>> --- >>> You received this message because you are subscribed to the Google >>> Groups "BeagleBoard" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
