Hi,
I have a watch project in mind. I just want to show the time when I press a button using a few LEDs in binary. I want to make it as compact as possible so I want to try to use the micro controller as a real time clock (RTC). I got the idea from sparkfun and their BigTime watch.
Product: https://www.sparkfun.com/products/11734
Source: GitHub - sparkfun/BigTime: Open source watch kit
From my understanding, they're running the 328p with their Arduino Pro 3.3v 8MHz bootloader and are using a 32.768kHz as an external crystal clock source.
I've found only a few other similar projects. Including some questions on this very forum.
http://forum.arduino.cc//index.php?PHPSESSID=4s1a2a1s9dfeu9af07dc1k1si1&topic=123285.0
In which Nick Gammon made a few minimal working examples.
My question is what hardware do I need to program this? I've used the Arduino as ISP method a few times before to run barebone chips without an external crystal. I've also used a tiny85 once. From what I understand, the chip runs with the internal clock at 8MHz and switches to the external crystal when sleeping. So I guess I need to put the bootloader on there and adjust the fuses for my clock requirements and power saving tweaks. I read somewhere I might need an ICSP programmer instead of ISP like what the Arduino can do. From what I understand, ICSP is a serial programmer that provides a clock source for the chip.
I have on hand 2 Arduinos (one duemilanove and one uno), adafruit's arduino ISP shield and Adafruit's FTI friend (I kind of doubt this will be too useful for the inital bootloader burn and fuse change). Do I need an AVR programmer to do this?
Any thoughts on this are appreciated. I'm kind of puzzled so any kind of clarification would be great.