This barometer uses the absolute pressure sensor MPXA4115A, 12-bit A/D converter and AVR ATmega8. The source code and schematic are here. The result is displayed on graphical LCD with TOSHIBA T6A04 controller. In the first half are numerical value of actual pressure in milibars and on second half are bars that represent pressure in last 30 hours (15 bars with 2 hours measuring period). horizontal antermittent line represent pressure of 1000 mb.
Digital barometer: [Link] (This domain appears to be down for a while and I do not know other places where this project might be hosted, Sorry)