A new revision (2.1) of Duino644 is now available. The redesigned board features:
- real time clock could be either DS3231 (extremely accurate RTC from Maxim) or the "old" DS1307;
- the resistor-based voltage dividers for SD card have been replaced by 74AHC125 buffer chip;
- small prototyping area, for adding extra functionality (e.g. automatic dimming with photo-resistor, FM radio etc);
- power-indicator blue LED is now through hole (replaces the SMD).
Still in place are:
- ATmega644P (DIP package) with 40-pin socket;
- SD card socket;
- infrared receiver;
- piezoelectric buzzer;
- 3 push buttons;
- reset button;
- two 2x8-pin connectors for direct plug-in with the 2416 LED display from Sure Electronics;
- miniB USB as power connector;
- ISCP 6-pin header;
- 6-pin FTDI header;
- four 8-pin headers for expansion boards ("shields").
The photo below shows the assembled board.
But don't get too excited: there are also 2 "minor" (easy to fix, fortunately) glitches:
- the FTDI header is too close to the display connector, so that the board cannot be inserted completely into the display, unless a piece of plastic from the display's connector is chopped off, as shown below.
- pin 3 of DS3231 (INT/SQW) is connected directly to D2 (pin 3) of ATmega644P, as is the output of the IR receiver. Basically, the IR receiver and DS3231 INT/SQW share the same interrupt. I initially thought of having a switch (2-pin header shunt) to connect INT/SQW to D2, but I got carried away and forgot to add it. There are 2 fixes for this: either software (modify the ISR) or just cut off the trace (and keep the software unmodified).
If you buy the complete Wise Clock 2 kit, I will cut both the display connector and the trace for you.
Otherwise, the Duino644 kit will have the unaltered board.