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fivdi / pigpio

Fast GPIO, PWM, servo control, state change notification and interrupt handling with Node.js on the Raspberry Pi
MIT License
948 stars 89 forks source link

Its possible to determine period of pulses using the tick value from on('alert') - like frecuency calculator #128

Closed lucianobustos closed 3 years ago

lucianobustos commented 3 years ago

This is maybe a silly question but I want to measure the interval beetwen consecutive ticks. (aka. a frecuency calculator). I've took this portion of your example...

let endTick = 0; let startTick = 0xffffffff; btn.on('alert', (level, tick) => { endTick = tick; console.log((endTick >> 0) - (startTick >> 0)); // is this value acurrante to calculate the period?? startTick = endTick; });

I can apply some sampling techniques to get more accurate values and not on every "tick". But I want to know if this tick value count the interval beetwen 2 gpio.pulses/trigger...

Thanks.. this library it's amazing.

fivdi commented 3 years ago

The tick value is an unsigned 32-bit integer value representing the number of microseconds since system boot. This value wraps around the 32-bit space in just over an hour.

As such, it should be possible to achieve what you would like to achieve.

See also getTick().

lucianobustos commented 3 years ago

Thanks Brain again. Actually I have a LM393 sensor with a sequencer-wheel to read pulses & convert them to freq. but doing that with node process.hrtime() is horrible and sensitive. (any proc. task corrupt the measurement) I'm testing your library and looks promising...

Thanks for your support.