Electronic – Use PPS for UART and PGC/PGD on PIC32

In your case you can leave pin 6 of the PICkit unconnected. You wont need it. Pin 6 is, as far as I can remember, for devices that need a special codeword to get into programming mode.

You dont need to seperate the programming circuit from your rest of the circuit, when you follow some rules (See Section 3 of the PICkit 2 manual):

• You should take care, that the "VPP voltage slew rate is not slowed down". So dont put big capacitors on the reset pin or you will get in trouble.
• The signals of the PGD and PGC pins shouldn't be affected. The manual of the PICkit suggest the use of some resistors to isolate your signal (see the figure below, taken from the manual). But this depends heavily on your external circuit.

Your circuit looks fine. The 51.1 kΩ resistor and diode to Vdd on MCLR is a bit silly, but that's not getting in the way of the ICD reading the device ID. Two things to consider:

1. Make sure that you are trying to use the ICD3 as a programmer, not a debugger when you are just trying to program firmware that should stand on its own.

2. Maybe you are getting crosstalk between PGC and PGC? I usually put 100 Ω in series with the lines coming out from the PIC, followed by 47 pF or so to ground. That filters sharp edges the PIC can produce during readback, which can cross between the two lines. This is made worse by PGC and PGD being next to each other on the normal ICD cable. I often use a ribbon cable with a extra ground line between the two.

For more general demystification about PIC programming electrical considerations, see www.embedinc.com/picprg/icsp.htm.