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2006-02-03 by widescreen03608
Hi all, On the CAP0.3 input I have pulses from an encoder and I want detect both edges and generate interrupts. The signal is filtered so the rise and fall time are slow (don't know exactly how long, but surely within 1ms). Is it possible that no interrupt is generated on CAP0.3, because the signal is to slow? I didn't found any datasheets from Philips which this is described. Thanks for help
2006-02-03 by Tom Walsh
widescreen03608 wrote: >Hi all, > >On the CAP0.3 input I have pulses from an encoder and I want detect >both edges and generate interrupts. The signal is filtered so the rise >and fall time are slow (don't know exactly how long, but surely within >1ms). Is it possible that no interrupt is generated on CAP0.3, because >the signal is to slow? > >I didn't found any datasheets from Philips which this is described. > > > Aside from the datasheet thing, wouldn't it be possible to use a schmidt gate to drive the capture intput? Or some op-amp crossing-detector with hysteresis? Regards, TomW >Thanks for help > > > > > > >Yahoo! Groups Links > > > > > > > > -- Tom Walsh - WN3L - Embedded Systems Consultant http://openhardware.net, http://cyberiansoftware.com "Windows? No thanks, I have work to do..." ----------------------------------------------------
2006-02-03 by charlesgrenz
The real question is why the rise time is so long. A typical HEDS encoder sensor is in the 50 to 100ns rise and fall times. regards, Charles --- In lpc2000@yahoogroups.com, Tom Walsh <tom@...> wrote: > > widescreen03608 wrote: > > >Hi all, > > > >On the CAP0.3 input I have pulses from an encoder and I want detect > >both edges and generate interrupts. The signal is filtered so the rise > >and fall time are slow (don't know exactly how long, but surely within > >1ms). Is it possible that no interrupt is generated on CAP0.3, because > >the signal is to slow? > > > >I didn't found any datasheets from Philips which this is described. > > > > > > > Aside from the datasheet thing, wouldn't it be possible to use a schmidt > gate to drive the capture intput? Or some op-amp crossing-detector with
> hysteresis? > > Regards, > > TomW > > > > >Thanks for help > > > > > > > > > > > > > >Yahoo! Groups Links > > > > > > > > > > > > > > > > > > > -- > Tom Walsh - WN3L - Embedded Systems Consultant > http://openhardware.net, http://cyberiansoftware.com > "Windows? No thanks, I have work to do..." > ---------------------------------------------------- >
2006-02-03 by G B
I would think a high speed comparator, where you could set the precise rise and fall voltage values would be best. Glen widescreen03608 wrote:
> Hi all, > > On the CAP0.3 input I have pulses from an encoder and I want detect > both edges and generate interrupts. The signal is filtered so the rise > and fall time are slow (don't know exactly how long, but surely within > 1ms). Is it possible that no interrupt is generated on CAP0.3, because > the signal is to slow? > > I didn't found any datasheets from Philips which this is described. > > Thanks for help > > > > > > > Yahoo! Groups Links > > > > > > >
2006-02-03 by Leon Heller
----- Original Message -----
From: "Tom Walsh" <tom@...> To: <lpc2000@yahoogroups.com> Sent: Friday, February 03, 2006 3:19 PM Subject: Re: [lpc2000] Rise and fall time of capture inputs > widescreen03608 wrote: > >>Hi all, >> >>On the CAP0.3 input I have pulses from an encoder and I want detect >>both edges and generate interrupts. The signal is filtered so the rise >>and fall time are slow (don't know exactly how long, but surely within >>1ms). Is it possible that no interrupt is generated on CAP0.3, because >>the signal is to slow? >> >>I didn't found any datasheets from Philips which this is described. >> >> >> > Aside from the datasheet thing, wouldn't it be possible to use a schmidt > gate to drive the capture intput? Or some op-amp crossing-detector with > hysteresis? I've done that in the past with that sort of input. I then had a problem with multiple signals (like contact bounce) which I eliminated with software. Leon -- Leon Heller, G1HSM leon.heller@... http://www.geocities.com/leon_heller
2006-02-03 by Tom Walsh
Leon Heller wrote: >----- Original Message ----- >From: "Tom Walsh" <tom@...> >To: <lpc2000@yahoogroups.com> >Sent: Friday, February 03, 2006 3:19 PM >Subject: Re: [lpc2000] Rise and fall time of capture inputs > > > > >>widescreen03608 wrote: >> >> >> >>>Hi all, >>> >>>On the CAP0.3 input I have pulses from an encoder and I want detect >>>both edges and generate interrupts. The signal is filtered so the rise >>>and fall time are slow (don't know exactly how long, but surely within >>>1ms). Is it possible that no interrupt is generated on CAP0.3, because >>>the signal is to slow? >>> >>>I didn't found any datasheets from Philips which this is described. >>> >>> >>> >>> >>> >>Aside from the datasheet thing, wouldn't it be possible to use a schmidt >>gate to drive the capture intput? Or some op-amp crossing-detector with >>hysteresis? >> >> > >I've done that in the past with that sort of input. I then had a problem >with multiple signals (like contact bounce) which I eliminated with >software. > > > Yes, that is a given when dealing with mechanical contacts. They do bounce. As far as that goes, analog lines can "bounce", inductance. TomW -- Tom Walsh - WN3L - Embedded Systems Consultant http://openhardware.net, http://cyberiansoftware.com "Windows? No thanks, I have work to do..." ----------------------------------------------------
2006-02-03 by Leon Heller
----- Original Message -----
From: "Tom Walsh" <tom@...> To: <lpc2000@yahoogroups.com> Sent: Friday, February 03, 2006 6:25 PM Subject: Re: [lpc2000] Rise and fall time of capture inputs >>>> >>>Aside from the datasheet thing, wouldn't it be possible to use a schmidt >>>gate to drive the capture intput? Or some op-amp crossing-detector with >>>hysteresis? >>> >>> >> >>I've done that in the past with that sort of input. I then had a problem >>with multiple signals (like contact bounce) which I eliminated with >>software. >> >> >> > Yes, that is a given when dealing with mechanical contacts. They do > bounce. As far as that goes, analog lines can "bounce", inductance. It was an LED/transistor unit, not mechanical. Leon