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Suggestions for building a PIC dev. board?

Discussion in 'Microcontrollers, Programming and IoT' started by chopnhack, Dec 31, 2014.

  1. chopnhack

    chopnhack

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    I am interested in building a development board for PIC μcu's. I know that this is a broad area since it depends greatly on what PIC you are using and what i/o you want to use/have read in etc. This is where I am having the difficulty. I don't know what I don't know!

    What should I as a novice include in a developer board? As for chips, I am thinking of using the lowest pin count in production currently, say from 8 pin dip to 16 pin.
     
    Last edited: Dec 31, 2014
  2. Colin Mitchell

    Colin Mitchell

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    I have a very simple PIC12F629 development board.
    This is where you start if you want to get into PIC programming. I also teach assembly programming and have a library of routines.
     
  3. chopnhack

    chopnhack

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    Thanks Colin, do you have a link to your dev. board?
    I looked at the website, but find it hard to navigate. I don't think the pic below is what you are referring to and the other link had no photo's of the board.
    Thanks

    [​IMG]
    from: http://www.talkingelectronics.com/Articles/images/Prototype-2.jpg
     
  4. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
  5. chopnhack

    chopnhack

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    Apr 28, 2014
  6. Colin Mitchell

    Colin Mitchell

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    chopnhack likes this.
  7. chopnhack

    chopnhack

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    Thank you Colin for finding that! The pick lick is a very basic design, relying on a transistor to sink a current for each output. I liked the PIC Lab better - more variety of "peripherals".
     
  8. Colin Mitchell

    Colin Mitchell

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    "relying on a transistor to sink a current for each output." ?????????????????????

    You always need a buffer device when the current is more than 25mA.
     
  9. chopnhack

    chopnhack

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    I understand that each pin can only handle 25mA max current, I was conveying that the design was very basic in that all you see is each port with a transistor on it whereas other boards have various i/o assigned to different legs. The picklick seems to have been built solely for output.
     
  10. Colin Mitchell

    Colin Mitchell

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    "The picklick seems to have been built solely for output."
    What do you mean?????
    The PIClick has 5 inputs and 8 outputs.
    If you haven't already realised, the PIClick project is a play-on-words to the STAMP where the Stamp cost $18.00 to $45.00 for less performance.
     
  11. chopnhack

    chopnhack

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    Yes, I think its rather clever. To be clearer, other dev. boards have different modes of output whereas the PIClick's outputs are all tied to a transistor. That is what I was commenting about.

    Take for example, this board:
    [​IMG]
    http://gooligumshopcom.fatcow.com/shop/train-dev-boards/base-mid-train-board

    I see three transistors, presumably three outputs are serviced by these while, the other outputs go directly to the other devices via jumpers. The piezo, the 7 segment LED, etc.

    What is the rational for giving each output a transistor?
     
  12. Colin Mitchell

    Colin Mitchell

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    "whereas the PIClick's outputs are all tied to a transistor."

    The outputs are NOT all tied to a transistor.
    You can add anything to any of the outputs.

    In the development board above, you won't get much brightness out of the 7-segment displays without driving them via transistors.
    And even suggesting multiplexing without transistors is not the right way to go.
    My 4 digit up/down counter has transistors all around.
    I don't know what he is promoting in the development board above but the smallest PIC chip has 8 pins and the next has 18pins. He only has a 14 pin IC socket. It looks like the product "falls between two stools."
     
  13. chopnhack

    chopnhack

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    I think I see what you are getting at - the transitor's are there to boost the current, if you don't need as much current you can dial back the base resistor. That way if you need to power something that is in excess of the pic's capability, you can. Do I have this correct?

    The board above is just a small developer board to learn base and midline chips.
     
  14. Colin Mitchell

    Colin Mitchell

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    "if you don't need as much current you can dial back the base resistor."
    I don't know what you mean.

    The transistor is only taking 1mA and the output of the chip can be used for other purposes or other loads. Any of the outputs can be converted to inputs at any time during the running of the program.


    "The board above is just a small developer board to learn base and midline chips."

    Midline chips have 18 pins
     
  15. chopnhack

    chopnhack

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    If using the transistor to power an output device that requires more current than the PIC port can output, the transistor is used to provide the extra current. But if we don't need as much current to power the output device, we can reduce the current to the base of the transistor which will reduce the current flowing from collector to emitter, etc.


    My mistake, the website states, mid-range, not midline.
     
  16. BobK

    BobK

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    What is your purpose in making this "development board?" Are you talking about something that can take multiple different PICs and write an debug code, then put the PIC into place on a custom board for the final product? Or are you talking about a board that will have multiple capabilities and be used as the final board for different projects?

    Bob
     
    chopnhack likes this.
  17. chopnhack

    chopnhack

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    Thank you for the input Bob :) - I was thinking of creating a board to use for various projects as I learn PIC programming. I wanted to have the flexibility of scaling up to different chips as I expand my knowledge, but I would be content to produce a board with support for just the 8 pin dip for simplicity sake. The board is solely for prototyping, so I would be reusing it.

    My initial thoughts were to use a 40 pin zif with female header strips on either side of the zif socket. That would allow the flexibility to wire up any PIC configuration while still in DIP format. I realized as I had the thought that this would amount to nothing more than what an ICSP does in a final board. I had wanted the dev. board to have more I/O devices, but wasn't sure what I needed or even wanted having never used anything like this before. Like I said initially, I don't know what I don't know! I would think a few 7 segment LED's, perhaps a LCD, some simple LED's as indicators, a speaker..
     
  18. BobK

    BobK

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    Okay.

    I would not limit it to 8-pin PICs, you would run out of pins before you get to your third project. Even 28-pin ones get to be short on pins if you are trying to run a 7-segment display.

    If I were doing this (and I have been thinking about it) I would use a 44-pin TQFP because it has enough pins for many things and you can get a ****load of different PICs from 16F, 18F. 24F and 33ds families all with the same power and programming pins.

    A 40 pin DIP would be more limiting, but also feasible.

    Bob
     
  19. chopnhack

    chopnhack

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    Understood, I was just trying to start small to grasp the concept. I agree that 8 pin pic's are limited, but I think my knowledge is more limiting right now that the chip! As for the 44-pin TQFP, I think they are awesome, but breakout boards for these all require you to solder them to the board. Did you have an idea for a temporary swappable setup? I did see one that had a spring to push the pic down onto the breakout pins, but it was ~$170!

    I would love to collaborate with you, but it seems you are way ahead of me Bob ;) I still think something can be done with the 40 pin zif I have.
    Anyone have ideas?
     
  20. BobK

    BobK

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    It is not that difficult to solder a 44-pin TQFP. I have done several of them. It actually takes less time than soldering a 40 pin DIP because you just drag the solder across all of the pins then wick off the excess. You should try it. Get a breakout board of Ebay, look at some YouTube videos and you should be all set.

    Then, once you design the board, you can get 10 from China really cheap, and just make up a new board for each project.

    Bob
     
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