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Programming for an embedded app

Former Member

Background: I need to convert a 200 kHz encoder pulse train to 47.5 kHz. I tried using the Arduino Nano but it topped out at 8 kHz. Is used an ISR triggered on the rising edge of the encoder pulse and did floating point addition to determine when I should output a pulse. I know FP math in an ISR is not a good idea in general but it was simple math and the Arduino couldn't output faster than 8 kHz even w/o any ISR processing. Someone suggest using the Raspberry so I am attempting it. I have the Raspberry Pi 2 900 MHz system.

 

Main Questions:

  1. Is it possible to booth the system and auto load an executable w/o having to login? I want it to run like an embedded system.
  2. I want to write the code in my MS Visual C environment. How do I compile it for running on the Raspberry. Do I copy the code on to the SD card and compile and run on the Raspberry?

 

These are my main questions. I am a newbie using this and don't know all the specific steps from start to finish. I do have the Raspberry up and running but somewhat stuck after that. My internet is slow and it take forever to surf and find stuff. Is there one or two locations that can show me how to write a program from scratch. The Arduino code is less than 30 lines.


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  • 0

    You wont want to use a Raspberry Pi for this, its not a real time device.  I "heard" you can get a real time OS but never used it.  The overhead of the OS is going to cause issues with devices that need exact timed pulses.

     

    Feel free to post your code, I bet we can get it running faster.  if the arduino you are using is 8mhz perhaps a 16mhz version would work?  I am not so sure an ISR would be the way to go if this is the ONLY thing it is doing, it would be better to remove the ISR overhead IMO.  If you are using DigitalWrite etc you can get a major increase by simply using the pins IO ports instead.

     

    Finally, if that doesn't work you need a faster MCU, such as a chipkitP with a Pic 32 should do the trick.  Here is a quick vid I made of a speed comparison between the chipkit PI and the nano.  the same code you write for the nano should work directly on the ChipKit.  On top of that you can do the optimizations I mentioned above and have more than 10 fold increase in speed.

     

    ChipKit Pi Vs Arduinio Nano328 16mhz

    http://www.element14.com/community/videos/16140/l/chipkit-pi-vs-arduinio-nano328-16mhz

     

    You can also pick up a ChipKit UNO which is the same thing just a different layout.  Both are pretty cheap, I think the chipkit pi is cheaper.

     

    If you find this information helpful or correct, please may "helpful" and/or mark as "correct answer".

     

    Thanks!

Reply
  • 0

    You wont want to use a Raspberry Pi for this, its not a real time device.  I "heard" you can get a real time OS but never used it.  The overhead of the OS is going to cause issues with devices that need exact timed pulses.

     

    Feel free to post your code, I bet we can get it running faster.  if the arduino you are using is 8mhz perhaps a 16mhz version would work?  I am not so sure an ISR would be the way to go if this is the ONLY thing it is doing, it would be better to remove the ISR overhead IMO.  If you are using DigitalWrite etc you can get a major increase by simply using the pins IO ports instead.

     

    Finally, if that doesn't work you need a faster MCU, such as a chipkitP with a Pic 32 should do the trick.  Here is a quick vid I made of a speed comparison between the chipkit PI and the nano.  the same code you write for the nano should work directly on the ChipKit.  On top of that you can do the optimizations I mentioned above and have more than 10 fold increase in speed.

     

    ChipKit Pi Vs Arduinio Nano328 16mhz

    http://www.element14.com/community/videos/16140/l/chipkit-pi-vs-arduinio-nano328-16mhz

     

    You can also pick up a ChipKit UNO which is the same thing just a different layout.  Both are pretty cheap, I think the chipkit pi is cheaper.

     

    If you find this information helpful or correct, please may "helpful" and/or mark as "correct answer".

     

    Thanks!

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