PICkit 2 Connection Questions

Thread Starter

tracecom

Joined Apr 16, 2010
3,944
Below is a clip from the Microchip PICkit 2 User's Guide.



In the third bullet point, I take this to mean that the PICkit 2 should be connected to a powered USB port at any time that the PICkit 2 is connected to a target board that has its own power supply.

Is my understanding correct? And if so, what would be the result if the PICkit 2 was not connected to a powered USB port, but was connected to a target board that has its own power supply?
 

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Markd77

Joined Sep 7, 2009
2,806
Maybe it makes the PICKIT work unreliably when it is plugged into USB. If there's just a resistor between the PIC in the programmer and the (powered) target PIC then the PICKIT PIC can be running. Current flows through the protection diodes so it can be powered even if VDD isn't connected.
I doubt if it would ever cause any damage, but best not to find out.
 

DerStrom8

Joined Feb 20, 2011
2,390
You are correct tracecom. Do not connect the PK2 to a power source (on the board end) if you don't have it plugged in via usb. My guess is that if you have, say, 9v on the board side and 0v on the USB side, it could cause some internal components to become reverse-biased when they should not be, and possibly cause damage. Poor design in that sense. I wonder if they fixed it for the PK3.
 

Thread Starter

tracecom

Joined Apr 16, 2010
3,944
Simon sez don't do that.

It's always best to follow his advice.
You are right, but I wish manual writers would accompany warnings with explanations.

"Don't do that!"

Why? Will my PICkit 2 or my circuit explode, smoke, or what? :)
 

t06afre

Joined May 11, 2009
5,934
You are right, but I wish manual writers would accompany warnings with explanations.

"Don't do that!"

Why? Will my PICkit 2 or my circuit explode, smoke, or what? :)
If you do this it is chance for that something may happen. What will happen will depend on very much on your circuit. Can not say more. If you find out you have done this error. Do not fix it by plugging in the USB cable. But disconnect the PICKIT from the board, then plug in the USB cable
 

Thread Starter

tracecom

Joined Apr 16, 2010
3,944
If you do this it is chance for that something may happen. What will happen will depend on very much on your circuit. Can not say more. If you find out you have done this error. Do not fix it by plugging in the USB cable. But disconnect the PICKIT from the board, then plug in the USB cable
Thanks. I had used the PICkit 2 a lot before I read this warning, so it's possible I did what I was not supposed to do. I don't specifically remember doing it, but it's possible.

But my PICkit 2 still works fine and I am not aware of any damage to my circuits, so, I suppose there's no problem.
 

Brownout

Joined Jan 10, 2012
2,390
Since the PICKIT2 is powered via USB, when you first plug it in, the state of the device is unknown, until it intializes. If you have it connected to a powered circuit, unknown things can happen when you plug in the USB cable. You might get away wiht it 100 times, then watch it go up in smoke on the 101st try.
 
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