Junebug and external power

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.

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

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

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!

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.

edeca said:

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.

Click to expand...

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

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