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List:       snap
Subject:    RE: [SNAP] Capture inputs
From:       "?.?p??????a?" <kostasb () compulink ! gr>
Date:       2003-10-21 8:52:56
Message-ID: 000801c397b0$cb09c800$0200a8c0 () Kostas
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Capture inputs,
It is a matter i was about to target in the near future
I was thinking to develop a software driver for small impact printer
mechanisms.
The weak point of such an implementation, is the capture of the horizontal
position of the printing head(s).
A photo sensing mechanism generates pulses as the head is moving
horizontally, at a frequency of 2-3kHz.
In the software driver, a counter counts the pulses from the starting point
(a limit switch) and drives coils accordingly.
You may want to consider this kind of application  as well

Best Regards
Kostas



-----Original Message-----
From: snap-bounces@geekythings.com [mailto:snap-bounces@geekythings.com]On
Behalf Of Christian Blixt
Sent: Tuesday, October 21, 2003 10:28 AM
To: SNAP list
Subject: RE: [SNAP] PWM input


Hi,

There are no timer or capture inputs on the SNAP. We might consider adding
some in the future if we can come up with a reasonable specification, since
there is nothing like this on the TINI we have nothing to look at.

If you can tell us more about your needs it could help us with this
specification. What pins on the SNAP would you like to use for PWM inputs?
Would PWM output also be of interest? What frequency of PWM are you using?

There is a technique that we have used at times to read PWM input, and that
you might be able to use in Java. If you just sample the state of the PWM
input a great number of times, at intervals that are uncorrelated to the
cycle time of the PWM input, you get a statistic reading of the duty cycle
of the input. Divide it with the number of samples taken and you will have
the duty cycle. This of course only works if the variations on the PWM input
are relatively slow.

Since the Cjip has no timer or capture hardware, this functionality has to
be realized in microcode (as a Veripheral). This imposes a limit on the
resolution to around 60 microseconds.

/Christian

Christian Blixt
Tel: +46 (0)8 594 110 82
christian.blixt@imsys.se

Imsys AB
Tel: +46 (0)8 594 110 70
Fax: +46 (0)8 594 110 89
www.imsys.se


> -----Original Message-----
> From: snap-bounces@geekythings.com
> [mailto:snap-bounces@geekythings.com]On Behalf Of SnofruTech - Kasper
> Hauge
> Sent: den 20 oktober 2003 16:02
> To: snap@geekythings.com
> Subject: [SNAP] PWM input
>
>
> Hi
>
> According to the CJIP data sheets Veripherals should be able to
> use inside the CJIP. I do need a timer Veripheral to make some
> PWM or capture inputs. I need to measure 2 or maybe 4 PWM inputs
> at the same time.
>
> Can any one help me getting started with this. I cant find any
> API's that should support this. I have a ToturIO board.
>
> Best Regards
> Kasper Hauge
>
>
>
>
> SnofruTech
> Drosselvej 1
> 9560 Hadsund
> Denmark
> phone: +45 96520052
> URL: www.snofrutech.com
>
> _______________________________________________
> Snap mailing list
> Snap@geekythings.com
> http://geek.ody.ca/mailman/listinfo/snap
>
>


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