PIC16F690 board layout?

Discussion in 'Embedded Systems and Microcontrollers' started by Guinness, Jan 17, 2010.

  1. Guinness

    Thread Starter Member

    Dec 31, 2009
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    Hi,

    This is such a simple question, but I cant find anywhere on the whole internet that can answer it.

    I have the pickit2 that comes with a PIC16F690.
    I have done all the lessons that came with it and now want to start doing my own things.

    There are 6 pins going from the pickit2 to the actual pic, now after I have programed the pic, I want to move it from the demo board to a circuit, but I cant figure out what I need to connect to the pins apart from a +5v and ground pin.

    Some places say the MCLR needs to be connected to +5v direct, others say there needs to be a resistor there.

    Some places say I need to put caps on some pins, but don't say which ones.

    I am totally confussed with just how to wire the thing up, if it helps, could someone just show me a simple circuit that connect to a few LED's please, just so I know what connections and external components go where.

    Thanks
     
  2. Guinness

    Thread Starter Member

    Dec 31, 2009
    81
    1
    Thats makes sence, now I understand why some have the resistor and some don't, im assuming there would be a momentary push button to connect it to ground to reset it then?

    Ok, im guessing the cap is used to smooth out any noise in the line before it goes to the pic?
    If it is, then does that mean it needs to be placed as close as possible to the pic?
     
  3. t06afre

    AAC Fanatic!

    May 11, 2009
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    By the way Gunnies, you know that the PICKIT 2 are made for in circuit programming. This mean you can program your uC in circuit. So you do not have take the uC in and out of the demo board every time you program it.
    The PICKIT 2 can also program a quite large range of the Microchip uC and even some DSP controllers. You do not have to use the 16f690 chip in every project :)
    If you need some help with the in circuit programming just ask for help
     
  4. Guinness

    Thread Starter Member

    Dec 31, 2009
    81
    1
    Oh, ok, will look into the range of pics it can program then, cheers.

    I will have to remember to put a switch on my circuits to change to a header pin or something that the pickit2 can plug into. I have the wireing drawing of the demo board, so should be able to figure out which pins go where.

    I will deff be doing that, still trying to get my head around some of the special functions it can do.

    Cheers for the info
     
  5. t06afre

    AAC Fanatic!

    May 11, 2009
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    THE "PICkitTM 2 Microcontroller Programmer USER'S GUIDE" Will tell you how to create ICSP interface. Just read it carefully, and be sure you have absorbed every detail regarding isolation of the pins used by the ICSP interface. A simple but safe method is to use jumpers or perhaps DIP switches on some pins. But for the MCLR a diode or resistor should do it.
    I would highly recommend the ICSP method. Because jacking the PIC in and out of IC-sockets will represent a great mechanical wear and tear on both circuit board an the IC.
     
  6. Guinness

    Thread Starter Member

    Dec 31, 2009
    81
    1
    I have looked at the datasheet about how to connect the MCLR pin and im just trying to figure out where the reset switch would go!

    It says its best to use a RC network, with the resistor between the power line and the MCLR pin, and the cap between the MCLR pin and ground.

    It shows what I think is the switch right next to the MCLR pin, but I thought the pin had to be took to ground and not just disconnected completely?

    Also would there not be constant power going from the power line to ground in that configuration? Or would the cap stop that as its in series and blocks DC?

    Sorry could not attach the info from the PDF file, the only option it gave me was to print the page. But if you have access to the datasheet, its page 203.
     
  7. Markd77

    Senior Member

    Sep 7, 2009
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    If I'm looking at the same diagram it says the capacitor is optional. It will block DC so no continuous current will flow.
    The bit that you think is a switch - if it looks like this [X] - then it is just the symbol for the pin and the switch isn't shown. The switch would go straight from the pin to Vss (although I've seen something that says a resistor should be in series with the switch).
     
  8. t06afre

    AAC Fanatic!

    May 11, 2009
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    Hi
    Which data sheet are you referring to then you say picture on page 203. I could not find any reset/MCLR info in the 16F690 data sheet, on that page. But I post a picture showing how to do it. You do not have to use this function. You may tie it to VCC internal and use the pin as an input. You can do this with the configuration bits setting.
     
  9. Guinness

    Thread Starter Member

    Dec 31, 2009
    81
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    t06afre - Thank you for the diagram, that makes everything clear now.
    I think I got the datasheet through RS website, maybe its layed out different.

    I do plan on doing that on final build, but while im making the circuit and learning the software side a bit more, I thought it useful to have a external reset switch. Just incase.

    Cheers for info, was very usefull.
     
  10. t06afre

    AAC Fanatic!

    May 11, 2009
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    You can controll this via MPLAB and PICKIT 2. In the toolbar(MPLAB) goto programmer and use the Release from reset, and Hold in reset options.
     
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