Jinx's static LCD drive solution
In a recent piclist message Jinx mentioned two methods he uses to drive static LCDs, and sent me the following to share. Click on the images for larger versions.
The 16F628 circuit is an up/down timer/clock, with optional dome bell or piezo bomb as the alarm
The two weak pull-ups on the ICM7211 data lines can be put in circuit by the user with jumpers, and those lines are read as '0' or '1' by the PIC, which then enables s/w routines if necessary.
Setting the display is simple - sequentially select digits with the 4017 and the 4-bit data on the data lines appears.
The Varitronix VI402 is almost identical to the Seiko SP505. It just has a couple of extra annunciators
The RC combination on the 4017 is for single-pin control. A long pulse on b6 will reset it by allowing the voltage on C to rise high enough. A short pulse will simply clock it. Try a few k for R and a few nF for C.
The Mode pushbutton selects between TOD clock/timer and 100ths
USB Clock is a project from the October issue of Silicon Chip
s/w is at