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Maximum port frequency ...


Best Answer mikepo, 28 August 2014 - 05:17 PM

I think we can safely exclude 100MHz and 2GHz, but you probably already knew that :)

500kHz looks pretty unlikely too ...

 

Does this help (towards the end of the post, under: "Bit toggling"):

 

http://informatix.mi...s/MeepMeep.aspx

 

 

It's not talking about Netduino in particular but the .Net Micro Framwork in general. But some good insights ...

 

"So basically, with a 100 MHz processor, you can usually do around 20 ?s wide pulses using managed code (about 25 kHz)."

 

Another similar discussion on the TinyCLR forum:

https://www.ghielect...?id=4052&page=1

 

"72 MHz sounds very fast.
But I was surprised that outputting an alternating 0 and 1 via .NET code was so slow!
I got only 10 kHz."

 

 

So I am guessing it would be less than 10kHz, if your code runs on the Netduino Go and communicates the command to toggle a pin to the shield base over the go!bus protocol ...

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#1 DaveFer

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Posted 27 August 2014 - 08:52 PM

Hi all. I apologize in advance if this topic has already been exhausted. I DID search prior to posting but I'm pressed for time.

 

What is the maximum frequency at which I can toggle a port on the Shield Base?

 

Please note:  This isn't a PWM quesiton. I'm not asking the minimum period or duty cycle or anything related to PWM.

 

The question is simply looking for the highest frequency that a port can be toggled steadily (turned on and off / high and low). 500 KHz? 100 MHz? 2GHz?

 

Thank you. Again, sorry if this has already been discussed and exhausted.

 

- Dave Ferreira



#2 theTroll

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Posted 27 August 2014 - 09:42 PM

A lot of that depends on what else you are doing.  If all you are doing is fliping the port, you can do it a lot quicker than if you have a lot of other stuff going on.  So it is not something that can really be answered because no one can know your code.



#3 DaveFer

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Posted 28 August 2014 - 04:04 AM

Sure. Of course it's unanswerable if there are other processes taking up cycles. Thanks.

I'd like to get a ballpark idea of the maximum frequency I can toggle the port with NOTHING else going on. A theoretical limit if nothing else.



#4 mikepo

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Posted 28 August 2014 - 05:17 PM   Best Answer

I think we can safely exclude 100MHz and 2GHz, but you probably already knew that :)

500kHz looks pretty unlikely too ...

 

Does this help (towards the end of the post, under: "Bit toggling"):

 

http://informatix.mi...s/MeepMeep.aspx

 

 

It's not talking about Netduino in particular but the .Net Micro Framwork in general. But some good insights ...

 

"So basically, with a 100 MHz processor, you can usually do around 20 ?s wide pulses using managed code (about 25 kHz)."

 

Another similar discussion on the TinyCLR forum:

https://www.ghielect...?id=4052&page=1

 

"72 MHz sounds very fast.
But I was surprised that outputting an alternating 0 and 1 via .NET code was so slow!
I got only 10 kHz."

 

 

So I am guessing it would be less than 10kHz, if your code runs on the Netduino Go and communicates the command to toggle a pin to the shield base over the go!bus protocol ...



#5 DaveFer

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Posted 29 August 2014 - 04:23 AM

Thanks, Mike. Yeah, that's the info I needed.

 

So, I'm not going to be able to create any kind of radio signal by toggling a port on the Netduino ... at least not in the amateur bands (2 meter band). That would require about 145 MHz.

 

I would have to create some dedicated tank circuit and then perhaps manipulate it using the Netduino. :)

 

   - DF



#6 CW2

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Posted 29 August 2014 - 01:21 PM

So, I'm not going to be able to create any kind of radio signal by toggling a port on the Netduino ... at least not in the amateur bands (2 meter band). That would require about 145 MHz.

 

You should have mentioned that in the original post - Shield Base has STM32F205 microcontroller that runs at 120 MHz, Netduino Go STM32F4 at 168 MHz. So, not enough for 145 MHz pin toggling even when done in assembly...






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