In the video above, I show how I programmed the assembled kits as well as the raw TQFP IC’s without soldering anything to them. It’s a pretty simple setup, but solved the problem I was facing as well as made things a lot faster. As I mentioned in the video, pogo pins are found here, USBtinyISP here, and breadboard switch here (from Adafruit).
A note on using ICSP: – The Square Inch is designed to accept an FTDI connection for programming. Because of this, a .1µF capacitor is between the reset line of the ATmega328P and the pin labeled DTR. This is so when you load new sketches on the Square Inch, it will reset automatically via the DTR line on the FTDI adapter. When you use ICSP, you need to bypass this capacitor! Otherwise it will not work. The programming board I used in the video had the capacitor bypassed with solder (pictured below). There is also a via to the right of the capacitor that leads to the reset line. This can be shorted to the DTR pin to accomplish the same task, as I did to program the assembled boards.
On the assembled boards, if you wish to change the bootloader or upload sketches via ICSP, you can temporarily short the cap using tweezers on the cap itself (green arrows) or the DTR pin and the via leading to the reset line of the 328 (red arrows) as shown in the picture below.