Temp-O-Clock
This is a compact little device that simply shows the time, date and temperature.
It uses an LCD display that I took out of an old Nokia 5110. Four blue SMD LEDs do the back lighting. The display runs on 3.3V and is very easy to interface via a synchronous serial bus.
The hardware is based on an Atmel tiny84, a DS1307 realtime clock with battery and a DS1621 temperature sensor (instead of using the tiny84's internal temperature sensor). The system runs on 5V with a 3.3V converter.
The etched and tinned circuit side. The PCB is 50 x 50 mm small.
All the settings and debugging are done over a one row header on the side.
This project was programmed using the flowchart styled assembler Algorithm Builder. It is a very efficient and fast way to program the AVRs. Here is the main routine:
Here is the I2C routine. The complete environment of Algorithm Builder is very powerful yet very simple to handle and the source code produced is very fast assembler. It also features a very good simulator with all the internal resources displayable. Visit the Algorithm Builder website for more information.