Junebug and external power

[edeca]

I have a 7805 circuit powering the PIC, but ICSP doesn't seem to work ("No device detected") when powering from this. With either +5V or U5V from the Junebug, ICSP works fine.

Do I need to do anything special if powering my circuit from an external +5V and GND? I have tried forcing target power in PICkit2, but this doesn't help.

 

[Nigel Goodwin]

What else do you have connected?, the PICKit2 helpfiles show how to connect it for ICSP, have you followed that?.

 

[blueroomelectronics]

A genuine Junebug will detect the target voltage and not supply it's own power to the target. If your target.

 

[edeca]

Sorry, that wasn't very clear. In all cases, VPP->VPP, PGC->PGC, PGD->PGD. I don't have a pull-up for MCLR from the positive voltage whilst I'm testing.

This works:

+5V from ICSP to VDD
GND from ICSP to VSS

And this doesn't:

+5V from external power to VDD
GND from external power to VSS

No other pins are connected on the PIC. I haven't connected +5V/GND (external) to +5V/GND on the ICSP header, but have tried with "force target power" in PICkit2. Should these two be connected?

I either get "No device detected" or "Unsupported part (ID=FFF0)" in the second case.

In the long run I'm thinking I'll just build a breakout board with the 18F1320 ports on stripboard and a proper ICSP connector, breadboard can be a pain!

 

[edeca]

OK, so my problem was that external +5V and GND weren't connected to the ICSP header. I didn't realise this was required and was worried about breaking a USB port (or more!). It does show this in the PICkit2 manual, I hadn't checked.

Thanks Nigel & Bill.

 

[Nigel Goodwin]

OK, so my problem was that external +5V and GND weren't connected to the ICSP header. I didn't realise this was required and was worried about breaking a USB port (or more!). It does show this in the PICkit2 manual, I hadn't checked.

5V isn't absolutely required, but ground certainly is - without it you have no connection to the board at all.

 

[edeca]

Oh yes, that does work too! I'll remember that if I come to making a breakout board for the 18F1320 pins.

Thanks again for your help, simple electronics seems to get the better of me every time