AVR-Chat

Don,

Your point is well taken.  The standard 10-pin JTAG connector has two grounds, both power for the interface device and target power sense and an unused pin.  So, only seven are actually necessary: the four JTAG signals, ground, target power sense and reset.  Using an adapter of some sort, it is always possible to reduce the physical size of the connector and I have used 0.05 inch pitch, single-row headers for exactly this purpose.  Plus, you can stick a single-row header in a row of holes, press it to one side and get pretty good contact.

There's still the issue that PDI requires only four pins.  The local Atmel applications engineer says that the only reason to use JTAG in preference to PDI on the ATxmega family is chaining.  I could justify being in a rut using only JTAG when it had clear advantages over the alternatives, i.e. ISP (screw up the fuses and you're in trouble) and debugWIRE (slow and awkward).  I don't need chaining, so if PDI is as good as JTAG (and, so far, it seems to be) I should get over my love of JTAG and use PDI.

Nothing is cast in stone yet.  Actually, I'm having trouble with the battery charger - my MAX1873 won't do what the data sheet says it should do.

Graham.