Is this correct

Discussion in 'Programmer's Corner' started by R!f@@, Nov 5, 2011.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    see the attached.

    I am really confused here :confused: ..this is a part of my C course module 2 which I am banging my head right now. :D

    Does the written paragraph matches the diagram about how the diode is really doing what it suppose to
     
  2. Markd77

    Senior Member

    Sep 7, 2009
    2,803
    594
    Sounds about right. I think the programming voltage is about 12V so the diode protects against 12V being applied to the 5V line, which is probably connected to a few other things that woudn't like it.
    Or don't press the button while programming.
     
  3. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    and just omit the diode.
     
  4. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    Shooot !.. I completely forgot about the 12V programming voltage.
    Thanks guys
     
  5. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    The question is do you really need a reset button in your application. If you do not need it. Then just drop it. Many newer PICs give the option to disable the reset input and use it as a standard input instead
     
  6. BillO

    Well-Known Member

    Nov 24, 2008
    985
    136
    @t06afre

    It says that RA5 is configured as an input. My guess is they are trying to show how a signal to that pin should be connected if in-circuit programming is to be allowed.
     
  7. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    @t06afre
    I think you missed it...
    That is not a reset button.In PIC's reset happens when you give a low logic at reset pin.They are always connected form MCLR pin to Vss (GND).
     
  8. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    Yes I see it now. I did not read the schematic properly. My bad.
     
  9. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    I think I missed something too...

    @R!f@@
    In the schematic a 10K pull down resistor has been used from MCLR pin to GND,it should not be their,it should be a pull up resistor from MCLR to Vdd (+5V).Something like this...
    [​IMG]
    EDIT:
    Here S1 is used to reset the mcu

    Good Luck
     
    Last edited: Nov 6, 2011
  10. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    Can also add. That the programmer hate capacetive loads. On any pin used by the ICSP. And the PICKITs can not offer much "drive" for the pins used in the ISCP interface. This document will offer some more light on the problem see section
    IN-CIRCUIT SERIAL PROGRAMMING™ (ICSP™) CONSIDERATIONS​
     
  11. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    Bugger....

    I destroyed two F88's.Now they are not even showing their device ID in willempro.

    This is what I am paying for ????
     
  12. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    Ha !! Got ya......we'll see from now on. :D
     
  13. BillO

    Well-Known Member

    Nov 24, 2008
    985
    136
    No. Read what it says. That pin is defined as an input, not a reset. The circuit shown by Rifaa is fine, given that.


    Edit:

    Sigh!

    Rifaa, the answer is yes. The schematic and the text show/say the same thing and are correct. In this case RA5 is being used as an input wherein it monitors whether or not the switch is activated or not. It is a completely valid situation and would work just fine as is shown. No changes are required. It is not supposed to be a reset circuit.
     
    Last edited: Nov 6, 2011
  14. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    Hey Bill, I never realized u are a Mikro guy.
     
  15. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    Oops I didn't read what was written on the schematic,but normally reset pin is not used for input they should be used for reset and programming...I never use them as input.Anyway you can do that...
     
  16. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718

    This is correct, but the MCLR_OFF config bit (different names in different compilers) must be set in the code so resets via MCLR going low do not occur.
     
  17. BillO

    Well-Known Member

    Nov 24, 2008
    985
    136
    Yup, in all the way's that count :D.

    Been at it since the Intel Z80 was just released. My first forays involved these older 8 bit CPUs. Then in the early 80's was part of a team that designed and manufactured a teleprinter (remember those?) that had a Z80 at it's core and two 8051 MCUs to run the paper punch/reader and the printer.

    As it stands right now, I am trying to get a company off the ground that designs, manufactures and sells tools to support the modern MCU industry.

    This is a picture of our first product. It is a programmer for the 8, 14 and 20 pin PICAXE MCUs aimed at getting rid of the rat's nest normally associated with getting them up and running. It connects to the computer with RS232 cable or a $3 USB to RS232, rather than the $20 kludge cable from the PICAXE folks and will sell for around $10 fully assembled.

    [​IMG]

    Features:

    Professional work flow
    Allows use of unregulated wall-wart type power supply
    Reduces kludge and clutter
    ZIF socket reduces wear and tear on the MCU
    Provides access to all signals
    Quick, easy and reliable connection to the PC using a inexpensive RSR232 cable or USB to RS232 cable.
    Etc...

    Sorry for the plug, but there will be more coming. All based on the complaints and problems I have seen folks suffer through on the forums around the globe. We'll be addressing solutions to problems with most of the MCU families and making this easier for all. Hopefully we'll get all the operational 'business' stuff sorted out within the next 6 months and be actually able to start shipping some of this stuff.
     
    Last edited: Nov 7, 2011
Loading...