No real help, just a bit of smartassing... ;-)
On certain chips like PIC18fxxk22 or PIC18Fxxk42 (and probably some more) the
timer can run on the full Fosc speed. That is up to 64MHz. So a resolution of
around 16 nanoseconds is possible. Of course the 16 bit timer then overflows
after about one millisecond. You can reduce the resolution by prescaling, or
catch the overflows using the timer interrupt to increase an additional
counter. As JAL allows variables of up to 256 bytes, you can capture times of
about 2.5*10^607 years, even at the full resolution. The universe exists since
about 5*10^9 years, so that should suffice all needs.
Greets,Kiste
Am Samstag, 5. September 2020, 09:55:03 MESZ hat Jesito's μFabLab
<[email protected]> Folgendes geschrieben:
Many thanks Rob. I have to figure out how to do it. Is the timer working at
the MCU clock speed?. If so the 16 bit value might be too small to hold the
pulse length for i.e. a 5 sec pulse, isn't it?. I suppose some prescaling
should be done there... Have to investigate and read more on that.Kind
regards.Jes.
El jueves, 3 de septiembre de 2020 a las 18:51:51 UTC+2, [email protected]
escribió:
Hi Jes,
I just checked but I was mistaken, there is a procedure that calculates a value
for the timer based on a frequency.
If you want to measure the length of a pulse you can use the capture mode of a
timer which is available in many PICs, for example the 16F1823.From the
datasheet:Capture mode makes use of the 16-bit Timer1resource. When an event
occurs on the CCP1 pin, the16-bit CCPR1H:CCPR1L register pair captures
andstores the 16-bit value of the TMR1H:TMR1L registerpair, respectively. An
event is defined as one of thefollowing and is configured by the CCP1M<3:0>
bits ofthe CCP1CON register:• Every falling edge• Every rising edge• Every 4th
rising edge• Every 16th rising edgeWhen a capture is made, the Interrupt
Request Flag bitCCP1IF of the PIR1 register is set. The interrupt flagmust be
cleared in software. If another capture occursbefore the value in the CCPR1H,
CCPR1L register pairis read, the old captured value is overwritten by the
newcaptured value.
Kind regards,
Rob
Van: [email protected] <[email protected]> namens Jes
<[email protected]>
Verzonden: donderdag 3 september 2020 13:45
Aan: [email protected] <[email protected]>
Onderwerp: Re: [jallib] Some help needed to measure pulse length Thanks Rob, I
look for it, just what I needed to know :0)
El jue., 3 sept. 2020 12:01, Rob CJ <[email protected]> escribió:
Hi Jes,I thought there is already a Jal library to measure the width of a pulse
created by Matt. Would that do the job?
Met vriendelijke groet,Rob Jansen From:[email protected]
<[email protected]> on behalf of Jesito's μFabLab <[email protected]>
Sent: Thursday, September 3, 2020 10:49:48 AM
To: jallib <[email protected]>
Subject: [jallib] Some help needed to measure pulse length Hello,I'm new to JAL
and I would like to measure the length of some pulses that can be as long as 5
sec and as short as 1/8000 of second.I have a handful of different pics, but
ideally I would like to use a small one, I just need one pin for the pulse, two
more to interface to an I2C small display and one more to reset and restart the
measure.Could anyone point me to an example that could guide me through this?.I
love the cleanless and simplicity of JAL.Thanks in advance.Jes.
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