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Hot!MPLAB Pickit 4 is a disaster

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acharnley
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2019/07/03 11:41:32 (permalink)
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MPLAB Pickit 4 is a disaster

Try this, remove the USB cable from your PK4 but leave the header attached. This replicates what we programmers have to do every 30 seconds when the PK4 crashes.

Ensure you have a voltage source connected to Vref+ or similar. 

Now watch as the PK4 shorts VCC/VSS causing current to surge through the attached PIC and kill it.

The PK4 should be revoked, fixed and reintroduced without this very stupid hardware bug.
post edited by acharnley - 2019/07/03 11:49:24
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    PStechPaul
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    Re: MPLAB Pickit 4 is a disaster 2019/07/03 13:32:31 (permalink)
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    Is there a schematic available for the PICkit4? I tried to find one but it seems only the PK2 and PK3 have schematics available. Have you traced any of the circuit to show what component(s) may be causing the short?
     
    And if the short is from the Vdd to the Vss pin, how is the current surging through the target PIC? The only way I can see is if there is a large charged capacitor on one of the PIC's I/O pins, so that the short across Vdd/Vss would cause it to discharge through the protection diodes.
     
    [edit] Now I see that there needs to be a voltage source (or perhaps even a capacitor) on the Vref pin. That might provide the mechanism for destruction.
    post edited by PStechPaul - 2019/07/03 13:35:13

     
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    ric
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    Re: MPLAB Pickit 4 is a disaster 2019/07/03 13:41:04 (permalink)
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    Agree it is poor design in the PK4, but it also indicates that you are violating the PIC's ABSOLUTE MAXIMUM RATINGS which state no pin (apart from MCLR) may receive a voltage more than 0.3V above VDD.
     

    I also post at: PicForum
    Links to useful PIC information: http://picforum.ric323.co...opic.php?f=59&t=15
    NEW USERS: Posting images, links and code - workaround for restrictions.
    To get a useful answer, always state which PIC you are using!
    #3
    acharnley
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    Re: MPLAB Pickit 4 is a disaster 2019/07/03 23:51:57 (permalink)
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    This is true ric, but in reality the PK4 crashes almost continuously and we don't want to unhook, pull the PIC etc. 

    I also have the SNAP which doesn't have the issue, and the main difference is the buck/boost power circuit. The low impedance suggests a FET is activating/oscillating in it.
    #4
    NKurzman
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    Re: MPLAB Pickit 4 is a disaster 2019/07/04 00:45:00 (permalink)
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    You are always supposed to connect the USB to any of Microchips debuggers before connecting it to a powered target.
    #5
    acharnley
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    Re: MPLAB Pickit 4 is a disaster 2019/07/04 01:50:19 (permalink)
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    I know that, but reality dictates it needing frequent USB on/off cycling to fix the inherent stability issues. 

    If the PK4 can't supply the current and the PIC is powered externally (so not violating the condition RIC stated) one must hope to have a current regulated supply attached (easy to forget!) otherwise the PK4 is toast. In this situation I now switch to the SNAP first, the PK4 is only useful here when requiring HVP.

    Ultimately, the PK4 has too many stability issues and the hardware design is flawed. 
    post edited by acharnley - 2019/07/04 02:19:09
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    Jerry Messina
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    Re: MPLAB Pickit 4 is a disaster 2019/07/04 03:38:55 (permalink)
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    it needing frequent USB on/off cycling to fix the inherent stability issues

    I haven't used the PK4, but with the other tools I find that using the "Refresh Debug Tool Status" button (the two circular green arrows) in the mplabx dashboard usually works just as well instead of constantly plugging/unplugging the tool.
     
    I use it whenever I start to get flaky messages when switching devices, etc.
    #7
    LdB_ECM
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    Re: MPLAB Pickit 4 is a disaster 2019/07/04 05:34:51 (permalink)
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    I have the complete reverse the PK4 never plays up I had all those USB issues with PK3.
    I am on Windows 10 64bit what O/S are you using?
    #8
    acharnley
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    Re: MPLAB Pickit 4 is a disaster 2019/07/16 12:54:28 (permalink)
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    Today the PK4 has died. It took out a PIC16 beforehand, now it gets hot under USB power.
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    NKurzman
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    Re: MPLAB Pickit 4 is a disaster 2019/07/16 14:59:00 (permalink)
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    nigelwright7557
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    Re: MPLAB Pickit 4 is a disaster 2019/07/16 19:17:10 (permalink)
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    acharnley
    Today the PK4 has died. It took out a PIC16 beforehand, now it gets hot under USB power.


    My PK4 lasted a week.
    Back with PK3 now and same old problems.
    Its very touchy if I use a programming pin as an output i.e. PGEC on PIC32mz.
    I am forever having to unplug and plug back in USB connector.
    It also gets upset when changing device type to program.
    It often gets stuck downloading the new code to the PK3 for the new PIC.
    It struggles putting device into debugging mode.
    So I have to use an LED for debugging !
     
    #11
    NKurzman
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    Re: MPLAB Pickit 4 is a disaster 2019/07/16 20:14:12 (permalink)
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    Why would not expect cheap debugger to have issues when you drive the pins it is controlling?
    When you change the device it also should not be connected to the wrong target.
    #12
    acharnley
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    Re: MPLAB Pickit 4 is a disaster 2019/07/17 00:37:15 (permalink)
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    I've a much better solution. The SNAP boards cost just £5 each and I've bought 10 then hotwired a resistor between USB Vcc and the output so they're driven like the PK4. Two resistors do the same for 3.3v, job done. :)

    I've put a claim in for the PK4 and I'm on the lookout for an ICD3.

    Andrew



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