Just got back the latest version of the Riffle 0.1.1 board, nicely assembled by the kind folks MacroFab.
Alas, when I used an ISP programmer to attempt to load a bootloader -- no dice! Didn't work.
I've been taught by folks that it's usually the case that a 'dead' board design can be brought to life with a few jumper wires ... so, I spent a while using a multimeter to track down the problem, and the main problem seems to be that I made a mistake when wiring up the switch that allows for changing battery chemistries.
The older, working version of the Riffle -- 0.96 -- had a simpler switch configuration:
(The full schematic for version 0.96 is here).
In modifying the board to accommodate two battery chemistries, in version 0.1.1, I think I goofed when assigning pins on the new switch:
(The full schematic for version 0.1.1 is here)
Basically, I misread the switch datasheet re: which pins on the switch would allow for connecting power appropriately. Oops. :( I'm going to go back and reread the datasheet on the switch device -- I might've confused part numbers or something -- but I can also simply do a compare / contrast between the older schematic + board layout and the current one to make sure that things are wired properly.
By properly connecting power across the switch (from VBAT -- which gets power from the USB via the lipo battery charger -- to VDD), I was easily able to load a bootloader:
But, after loading a bootloader, was unable to program the board with a sketch in the Arduino IDE, via USB as per normal. It gave a "avrdude stk500_getsync(): not in sync" error.
However, after playing around with a lot of iterations, I figured out that by connecting a battery to VBAT, I was able to program the board. Alternatively: if, instead of connecting VDD to VBAT, I connected VDD to to VBUS (i.e., directly to USB), I was also able to program the board successfully:
So, in addition to fixing the wiring on the switch (straightforward), there's some more subtle issue re: the power wiring on the board. I'm going to do some more testing with the multimeter tonight, and ask around tomorrow.
Favor -- anyone who has the time, could you check out the power circuitry on the board, and let me know if you see something dumb? :)