PICkit 2 Calibration

teaserThe PICkit 2 has a handy feature to vary the voltage supplied to a connected chip.  In addition to being needed to program low voltage parts, the ability to change VDD when using a PICkit 2 is very handy for testing things like the HLVD module.  The PICkit 2 must be calibrated to ensure the VDD setting is accurate.

The PICkit 2 is powered from the USB port; the voltage supplied by a USB port is nominally 5 volts but the voltage can be as low as 4.2 volts depending on the USB port used.  The PICkit 2 does not use a voltage reference for its ADC or for setting the VDD output voltage.  Without calibration, the USB supply voltage is assumed to be 5 volts - if it is not, the voltage setting and detection will be inaccurate.

The calibration procedure is simple, but requires a DC voltmeter.  The calibration will be accurate for only the USB port the PICkit 2 is connected to; if the connection is changed, the calibration should be checked and the procedure repeated if necessary.  The calibration voltage is stored in EEPROM.  Note that the USB supply voltage is the maximum that can be supplied for VDD; it has no ability to increase this voltage.

 Note:  Not all PICkit 2 clones are created equally.  Some clones have no provision to vary VDD.  The voltage may be changed in the GUI, but the output voltage will not change.

The Procedure

The calibration procedure requires only a few minutes and a DC voltmeter connected to pin 2 (VDD) and pin 3 (GND).

Meter Setup

 

The following screen shots show the process, starting from the PICkit 2 GUI.

GUI Screen


The first dialog box explains the need for calibration and when it should be repeated.

Cal Dialog

 

Heed the warning in the next dialog box.  Do not proceed if you do not have a volt meter connected.

Cal Dialog 2

 

Next, enter the voltage reading from the voltmeter and click the button to calibrate.

Cal Dialog 3

 

Optionally, you can give the PICkit 2 a name.  This is helpful if you have more than one.

Cal Dialog 4

 

That's all there is to the procedure.  And the result?  When I set my PICkit 2 to provide 5v VDD, I measured 4.933 volts, the maximum possible using my USB connection.

 

PICkit 2 Programmer/Debugger User's Guide

 


Posted: 4 years 9 months ago by lespic #12913
lespic's Avatar
Long live the PICkit2 , unfortunately I managed to kill one of my 2 units. It powers up but won't recognize any pic.. any ideas ?
Posted: 4 years 9 months ago by Jon Chandler #12914
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The PICkit 2 is pretty hard to kill. I would try reloading the firmware as described on page 61 of the operator's guide (link in the article).

Aside from that, the following may be helpful:

1. I have never had reliable operation with the PICkit connected to a hub with more than 4 ports. It will lose connections and behave erratically.

2. Use a powered hub if using a hub.

3. If the PICkit errors, disconnect it from USB, shut down the GUI and start over. This is the only way to reset the self-protection features caused by shorting the power, etc.


I noticed the manual cautions against connecting the PICkit 2 to a self-powered circuit if it's not connected to USB. Makes sense because the output pins would be exposed to greater than Vdd + 0.3 volts.

There were also some engineering changes made to the earliest units. If your PICkit 2 has a black button instead of a red button (and it's a real deal), Google for "black button PICkit 2" and you should find the necessary changes.
Posted: 4 years 9 months ago by jmessina #12916
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Have you run the test procedure built into the PICkit2 Programmer app? It's under the Tools | Troubleshoot... menu.

That, along with the schematic in Appendix B of the Users Guide should get you pointed in the right direction. If the USB side works, then likely it's a problem with the output transistors/fet switches on page 2 of the schematic.

If you go through the troubleshooting steps and report your findings, perhaps we can help more.
Posted: 4 years 9 months ago by lespic #12917
lespic's Avatar
Many thanks for the help . Seems it got worse since i last tried to revive the dead PK2 , now it's not working on USB either, and the 18F2550 not being seen by PK3 ! (I put a connector in J1 to try and burn a bootloader.) could be end of the road ,I could try to remove / replace PIC if i get stuck... Thanks again.

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