As I mentioned yesterday, I learned a little bit more about ISP, and so I learned not only how to run the Atmega328P without an external crystal timer, but also how to flash it on the fly. I’m pretty happy with this redesign right now, and don’t see it changing significantly. Possibly, another revision might replace the IC with a version of ATtiny, seeing as how eight ports are not used in this design. As far as the actual schematic is concerned, I’m pretty pleased with how orderly it came out, though I’m less pleased with how the ISP module connects to the Atmega328P: there are 11 crossing cables in there, due to the positioning of the AVR-ISP-6.
If I were to clean this up, I’d have to basically make a new symbol for the Atmega328p that would fit that general principle. PB0, PB3, PB4, PB5, and PC6 are better suited to be placed on the left side of the Atmega328p, considering they’re all set as inputs. That would make the whole image much cleaner as a result. I guess if I ever do end up making a fourth revision, I’ll clean that image up for a more final result.
Yesterday, I also managed to run my first succesful test of uploading an Arduino sketch using the USB programmer. I haven’t tried uploading directly through AVRDude just yet, because that would involve compiling my own code, which would be the next step. First, I wanted to see whether uploading itself would work. So, I hooked up my USB programmer to the Arduino Uno, and used the Arduino IDE to flash the Atmega328P via the programmer (for which it uses AVRDude in the background anyway). It went off without a hitch! I also tried setting the lfuse to 0xF2 to have it run on its internal clock, which results in the program running half as slow (as the internal clock is 8Mhz versus the 16Mhz external crystal). So, I did have to adjust some timers to have it run correctly again.