Pickit 3 modification help!

[Sajjadkhan]

Pickit 2 had a feature regarding PGT function that it uses target board supply to power itself, but this is not the case with pickit 3. i was wondering if solder a thin wire to pin 2 that is Vdd to 5v of its usb, then it should work. any thought before doing it?

 

[wp100]

Hi,

Can you clarify a few things.

You say the PK2, but are you talking about a Microchip one or a cut down clone.
On the Microchip Pk2 there is no way power from a target board and get back into the PK2 via VDD to power it, the Pk2 simply reads the voltage from VDD.
Most clones also have a protection diode in the line to VDD to stop the PICkit2 being powered by the target board.

Again not sure what you mean by PGT function ? see no reference to it in the PK2 Users manual or circuit diagram.

 

[Sajjadkhan]

well i am talking about orignal pickit 3, about pickt 2, i just heard it from somebody. PGT = programmer to GO function. In PGT mode you have to power pickit 3 via usb. it would be quite good if it takes power from Target board.

 

[wp100]

Hi,

Programmer to Go, right - don't have a PK3 only the Pk2, to use the PGT on the PK2 microchip suggest you use a battery pack on the usb socket !

What I did was disconnect pin 6 of the PK2 Output connector, its only used to program eeprom.
I then connected the USB+5v input rail to pin 6, the idea is that you can feed the target circuit with the direct 500ma of power from the PCs USB port; the Pk2 circuit can only supply 100ma max.

This also allows the PK2 to feed off a target board, if you connect pin6 of the icsp socket on the target board to its own +5v.
Of course its not a good modification to make if you expect other people to use icsp on your boards.

It also has the problem that if you have the PK2 connected to the PCs USB and to a powered target board then something will probably go bang when the to +5Vs meet !!

Do not know if you can do a similar thing on the PK3 ?

 

[Sajjadkhan]

Well pickit 3 can only supply 30 mA. you gave me another idea. how about if i disconnect pin 6 as u did and connect it with 5v of the usb and in my target board i provide 5v on pin 6. so power will be taken from pin6 of the target board to the 5v pin of usb and there you go, no need of extra power supply.

 

[wp100]

Well pickit 3 can only supply 30 mA. you gave me another idea. how about if i disconnect pin 6 as u did and connect it with 5v of the usb and in my target board i provide 5v on pin 6. so power will be taken from pin6 of the target board to the 5v pin of usb and there you go, no need of extra power supply.

Hi,

Seems the Pk3 Pin6 is for the LVP function which I expect you do not currently use.
It might be assigned more funtions in the future as they slowly improve the software.

I have not had chance to open a PK3, but my reservations would be that with so much circuitry it might be very difficult to work on the board without risk of damage.
As soon as you do work on the board, thats the end of your guarantee as well.

 

[tpetar]

There is PicKit 3 variants up to 450-500mA and in some variants is just up to 50mA.

 

[btbass]

If you look at the bottom of the board you will see a test point labled 'VBUS'.
This is connected to the USB incoming 5V. If you connect Pin 2 to this via a diode, (anode on Pin 2), you could power the PicKit3 from the target power supply.

 

[wp100]

If you look at the bottom of the board you will see a test point labled 'VBUS'.
This is connected to the USB incoming 5V. If you connect Pin 2 to this via a diode, (anode on Pin 2), you could power the PicKit3 from the target power supply.

Hi,

But make sure you use a Schottky diode otherwise the voltage drop will be too large.

 

[Sajjadkhan]

If you look at the bottom of the board you will see a test point labled 'VBUS'.
This is connected to the USB incoming 5V. If you connect Pin 2 to this via a diode, (anode on Pin 2), you could power the PicKit3 from the target power supply.

But i wonder there is a reason to put that diode. yes i agree that we can do it till your voltage is up to 5V. i think the reason to put that diode there is to make sure that if user misshandle its target board voltage then it wont effect the pickit i.e. if V_targetboard >5v(+- 10%).

 

[btbass]

The diode is there so that the PicKit can still be used with the USB as normal.
When you plug it into the usb port on the pc, the diode blocks the usb 5 volts going to the target.

Powering the PicKit from the target will only work for 5V devices.