PIC16f72 VPP error problem

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Aashitech
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2008/09/14 14:42:06 (permalink)
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PIC16f72 VPP error problem

hi,
This is my first post in this forum,I recently got a pickit2 with red button...though it seems to program devices like 16f676,16f785 etc but it gave error "VPP error" when ever i inserted a pic 16f72 device.As the read  me file supplied with pc software(i am using the latest software/firmware downloaded from mchip web site) suggest i even used external power supply for +5v but problem remains the same.The trouble shoot utility says that there is short at VPP but i am simply using this as a programmer,the mclr/vpp pin of pickit2 is directly tied to reset pin of 16f72 mcu,any there to shed some light on this?
post edited by Aashitech - 2008/09/14 14:52:04
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    PICkit2Dev
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    RE: PIC16f72 VPP error problem 2008/09/14 19:38:44 (permalink)
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    Where (into what) did you "insert" the PIC16F72?
     
    The problem is mostly either
    1) The PIC is improperly connected to the PICkit 2
    2) There is other interfering circuitry on the MCLR signal.  See Chapter 3 of the PICkit 2 User Guide.
    #2
    Aashitech
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    RE: PIC16f72 VPP error problem 2008/09/15 01:42:34 (permalink)
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    the pic 16f72 is inserted into a zif socket mounted on a customised pcb I made just for programming purpose.The mentioned pcb has seprate zif sockets for 14,16,18,20 DIP/28 DIP packages.Its a very simple scheme even no othere active/passive component is there,just putted zif sockets and wired them to an edge connector as per pickit 2 specification.The fact that its programming all parts like 16f785,16f676 makes me confident that there is`nt any board or wiring problem.As pickit 2 readme file says that 16f72 requires a minimum of 4.75 v for progrraming I even gave external power supply of +5v but problem remains same.I dont know why but VPP voltages are getting suppressed as can be observed from troubleshoot utility of pickit2 programming software.
     
    Regards
     
    SAIF ULLAH KHALID.
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    FunnyNYPD
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    RE: PIC16f72 VPP error problem 2008/09/15 04:40:55 (permalink)
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    Have you checked the pin-out of those chips? Also recommend connect all Vdd and Gnd on the chip with your ICSP wires.
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    Aashitech
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    RE: PIC16f72 VPP error problem 2008/09/15 05:33:01 (permalink)
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    yes all supply vss & vdd are tied together and connected to pickit2 connector.
     
    Rgrds
     
    SAIF ULLAH KHALID.
     
    www.aa****echnologies.com
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    PICkit2Dev
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    RE: PIC16f72 VPP error problem 2008/09/15 08:30:39 (permalink)
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    the pic 16f72 is inserted into a zif socket mounted on a customised pcb I made just for programming purpose.The mentioned pcb has seprate zif sockets for 14,16,18,20 DIP/28 DIP packages.Its a very simple scheme even no othere active/passive component is there,just putted zif sockets and wired them to an edge connector as per pickit 2 specification.The fact that its programming all parts like 16f785,16f676 makes me confident that there is`nt any board or wiring problem.


    The PIC16F785 and PIC16F676 are different pin size packages and pinouts from the PIC16F72.  Since you have different ZIF sockets on the board, it is quite possible that while the 14/20 pin ZIF socket(s) for these devices is working, there is a connection problem with the 28-pin socket used for the PIC16F72.

    Try using "troubleshooting" without any PIC inserted in your programming PCB.  If the VPP error disappears, you can be fairly certain the issue is with ICSP signals (most likely MCLR/VPP) misconnected to the 28-pin socket.
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    Aashitech
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    RE: PIC16f72 VPP error problem 2008/09/15 09:21:43 (permalink)
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    as stated earlier that whenever 16f72 is present in socket the VPP test fails in "troublehsoot" but if its removed than the setup passes VPP TEST ,the value it reads at VPP pin are 12 VDC +/- 100 mv.

    Rgrds,
    SAIF ULLAH KHALID.
     
     
    EDIT : I throughly tested the wiring and found every thing perfect,what I concluded is that this part(PIC16F72)is drawing vpp currents not supported by pickit2 hardware...its just my observation...any one here in forum ever programmed PIC16F72 using pickit2?? 
    post edited by Aashitech - 2008/09/15 09:41:32
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    FunnyNYPD
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    RE: PIC16f72 VPP error problem 2008/09/15 12:08:17 (permalink)
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    Sounds like your PICKit2 is working, somehow the chip/sth is holding the Vpp pin.
    According to the data sheet, Most of the ICSP-Vpp-current required for PICs are less than 10mA. It should not be a big problem.

    Can you verify if the chip is damaged already, or sth else is holding the Vpp pin?
     You can do a quick resistor test with a multimeter.

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    Aashitech
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    RE: PIC16f72 VPP error problem 2008/09/15 12:29:39 (permalink)
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    yes i verified the device for permanent damage ,even checked with other devices but no sucess.The same device was programmed again with EPICwin programmer sucesfully,I regularly uses EPICwin programmer infact haS programmed more then 20,000 different device like 16f785,16f72,16f676 and 12f510 using this programmer in last one year.The only thing which attracted me for pickit 2 is its usb interface so that I can program devices on the move using my notebook.Lastly i would like to say that EPICwin is among one of the best programmers but its only negative point is paralell port interface.
     
    Rgrds,
     
    SAIF ULLAH KHALID
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    FunnyNYPD
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    RE: PIC16f72 VPP error problem 2008/09/16 18:30:07 (permalink)
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    Would you please run a PICKit2 voltage calibration as this tutorial (and let us know what's the calibration number for your system, on the following demo, it is 4.21):
    http://www.auelectronics.com/Q4.htm

    Another quick question is: what's the USB voltage on your computer? And how many USB devices on the computer? Do you share your USB port with other devices?

    I encounter a problem when there are 4 USB device on the same USB port via a hub, the USB voltage drops to about 4.2 volts. That creates some issue for PICkit2.

    BTW, what's the total length on your ICSP cable length from PICKit2 to the Chip? It is recommended less than 6 inches for best performance.

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    Aashitech
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    RE: PIC16f72 VPP error problem 2008/09/17 01:40:15 (permalink)
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    1)The usb voltage measured are 4.9x vdc.
    2)No other device is connected to any usb port.
    3)The distance between pickit2 and mcu pins is <= 4 inches.
     
    BTW,can you please verify whether your pickit 2 is ok with PIC 16f72.
     
     
    Regards,
     
    SAIF ULLAH KHALID
     
    www.aa****echnologies.com
    #11
    PICkit2Dev
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    RE: PIC16f72 VPP error problem 2008/09/17 12:04:18 (permalink)
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    Aa****ech,

    This part was tested with PICkit 2, and I have just retested and encountered no problems.  The PIC16F72 device VPP pin was only pulling about 700uA from the PICkit 2 VPP pin.  This device should not pull even close to the PICkit 2 VPP limit.

    I will suggest you measure the current being pulled from VPP by this device.  You can do this using PICkit 2's Troubleshoot dialog.  If you measure this with external supplies, ensure the 16F72 VDD is powered, PGX are both tied to ground, and put 12 Volts on VPP.

    If your PIC16F72 device VPP pin is pulling more than 2 mA or so, the device is likely damaged and should be replaced.  I understand other programmers with more VPP drive may still program it, but that does not mean the device is not damaged and performing to specification.

    If the PIC16F72 device is indeed pulling less than 2mA from VPP, then I would suggest you get the PICkit 2 unit replaced as it appears damaged or defective.
    post edited by PICkit2Dev - 2008/09/17 21:33:37
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