My project is a Propeller powered Holiday Countdown timer. It uses an RTC chip for accurate timekeeping, and an 8 digit alphanumeric LED display for the timer output.
The other hardware consists of 2 74HC595 shift registers, a DS1302 RTC (and supporting hardware), and a Gadget Gangster Propeller Platform. The shift registers are connected so that the first one controls all the basic numeric segments, and the second one controls the alpha segments. The program Ive written for the Countdown Timer consists of a text driver for the alphanumeric display, with all string, decimal, scroll, and print functions, along with the countdown function itself. The program looks up a data table with the dates on it, listed from first to last, and then finds the closest one and starts counting down to it. If the holiday is more than a month away, it displays months, days, hours, and minutes until the date. If its less than a month away, then it displays days, hours, minutes, and seconds. When the holiday is reached, the function looks up a string with a greeting for the holiday (Merry Christmas for example) that it will scroll on the display for the day. The downside to the device is that it does not handle day sensitive holidays, like Thanksgiving and Easter, that dont have a set date. The display driver is a combination of shift register output and multiplexing, shifting out the segments then pulsing them to the correct digit. The pulse width has been fine-tuned to 1/400th of a second. The device is driving the LED display from the shift registers only, no external driver ICs.
(The previous text was my Project Description)
I also have my schematic attached:
pictures are to come and there will also be an entry for this in the projects forum soon. I'll post my source code after the deadline is past.
Good luck to all,