techElder
Well-known member
"Wrecking" my brain trying to find the best way to make a selectable, multiple-period pulse generator that is crystal controlled. The 08M2 has enough pins, but I can't get it crystal controlled. Dang, I don't want to dedicate a 28 or 40 for a simple device like this.
I need at least two different periods, but three periods will be perfect. I can use two pins to get four periods with a little ingenuity in the switching.
Must plug into a powered port to provide the pulse to a timing circuit.
Periods range from 0.200 second to 2.000 second. The precision has to be good enough for a 500 uSec rounding that I do in the timer. I'm figuring on at least 3x better, so that would be around 167 uSec. 5x better would be 100 uSec. That would be even better.
So, I was figuring on working from a 1MHz oscillator derived from a 32MHz system clock.
I'm providing this pulse now with an 18M2, but not trying to get the precision --- just a test function.
I'm generating a PAUSE delay to create a negative-going pulse that is AC coupled to a MOSFET to get the negative-going signal output.
I designed (reserved) a little of the PAUSE delay so I can calibrate the output period by adjusting this reserved delay. Seems to work, but I don't think the PICAXE internal clock is real tight over temperature.
What are your thoughts?
I need at least two different periods, but three periods will be perfect. I can use two pins to get four periods with a little ingenuity in the switching.
Must plug into a powered port to provide the pulse to a timing circuit.
Periods range from 0.200 second to 2.000 second. The precision has to be good enough for a 500 uSec rounding that I do in the timer. I'm figuring on at least 3x better, so that would be around 167 uSec. 5x better would be 100 uSec. That would be even better.
So, I was figuring on working from a 1MHz oscillator derived from a 32MHz system clock.
I'm providing this pulse now with an 18M2, but not trying to get the precision --- just a test function.
I'm generating a PAUSE delay to create a negative-going pulse that is AC coupled to a MOSFET to get the negative-going signal output.
I designed (reserved) a little of the PAUSE delay so I can calibrate the output period by adjusting this reserved delay. Seems to work, but I don't think the PICAXE internal clock is real tight over temperature.
What are your thoughts?