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. Continue reading Programming the Square Inch – TQFP Jig
I have been working more with 3.3 volt projects lately and wanted to make programming them with an FTDI adapter as easy as possible. Sure you can switch most FTDI adapters from 3.3 to 5 volts (the FT232RL chip has a built in 3.3 output as well as logic level selection), but it involves scratching a jumper wire and soldering pads. This isn’t bad to do once, but to go back and forth is time consuming and rough on the boards.
So, I made my own FTDI adapter with an easily changed jumper for voltage selection. I also added a power LED to let me know that it’s plugged in and ready to go, threw in some RX and TX indicator LED’s and all required caps (read the data sheet), and mini SB jack. I ordered the boards from OHSPark.com, and as always, they were great.