pulse counter using usb1287

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msd
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Posted by msd: Thu. Aug 22, 2013 - 06:25 AM
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Hello to all,
I am trying to make pulse counter using usb1287 controller. The pulse output available has specifications: Max. Pulse rate : 3.3*10E5, Pulse width = 30ns and pulse pair resolution = 35 ns. Will AT90usb1287 Timer/Counter hardware be able to count it accurately?

Thanks.

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AVR Microcontrollers, megaAVR and tinyAVR
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Kartman
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Posted by Kartman: Thu. Aug 22, 2013 - 07:13 AM
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What does the datasheet say about externally clocking the timers? From memory the max rate is half the io clock rate. so 30 ns is too narrow. 330kHz is ok.

So what is "pulse pair resolution"? You might want to explain the application so we can understand this magic specification.

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msd
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Posted by msd: Thu. Aug 22, 2013 - 08:40 AM
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Thanks Kartman, I doubted that but want to confirm that so incase I am not missing trick unknown to me. The pulse pair resolution is the minimum time before a second pulse will be registered.
The application simply counts no. of pulses from PMT.
So can't count for pulsewidth = 30 ns...

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Kartman
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Posted by Kartman: Thu. Aug 22, 2013 - 09:42 AM
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I had to Google what you meant by PMT. I was sure it wasn't pre-menstrual tension! So, I gather it is a photo multiplier tube?

The 30ns pulse can be stretched easily, to say, 200ns but if the pulses come too quickly, you will lose count of some.

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msd
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Posted by msd: Thu. Aug 22, 2013 - 09:56 AM
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Kartman wrote:

The 30ns pulse can be stretched easily, to say, 200ns but if the pulses come too quickly, you will lose count of some.

Thats what reflect by Pulse pair resolution to be 30ns, so can't stretch the pulse as next pulse can be in next 35ns....
So, any idea/suggestion regarding possible solution...

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Kartman
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Posted by Kartman: Thu. Aug 22, 2013 - 10:07 AM
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Choose a faster microcontroller. Maybe something like a SAM4S,TI Tiva or STM32F4. you'll want to look closely at the specs regarding external clocking of the timer.

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msd
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Posted by msd: Thu. Aug 22, 2013 - 11:50 AM
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No one from AVR!!!!!!!!

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Gold Markclawson
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Posted by clawson: Thu. Aug 22, 2013 - 12:25 PM
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Quote:

No one from AVR!

Why would you use a 16/20MHz micro to do a 50..100MHz+ job? Atmel have Cortex processors up to 120MHz (SAM4S that Kartman mentioned for example. STM32 have a 168MHz Cortex M4). The cycle time at 120MHz is 8.3ns so you have several cycles available between 30ns events.

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msd
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Posted by msd: Thu. Aug 22, 2013 - 12:53 PM
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You are right, I was looking for controllers with my existing compiler support. Those are not supported :(

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Bronze Marktheusch
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Posted by theusch: Thu. Aug 22, 2013 - 01:31 PM
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So, how much does an 8-/10-/16-bit external counter chip cost nowadays? 74HC590 about $0.50; 24MHz. Does the datasheet indicate it would be happy with 30ns pulses? Yep.

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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msd
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Posted by msd: Fri. Aug 23, 2013 - 05:37 AM
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Exactly, I was googling for the same...thanks a lot theusch.. :P

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