4 digits working

The schematic is correct but the ICs are different. I didn't want to create the parts. The 7805 is ULN2803A. The displays are Kingbright SA56-21EWA and the CA are 3 &8. V1 is a 74HC238.

This is to drive the display with just 7 lines from the CPU. Each of the segment are driven by the
74HC238 3 to 7 decoder. You select the correct digit with the U4,U10,U17, and U18 control lines. This is different then most examples for a 7 segment display drivers. They would take 7 +4= 11 control lines. I would have rather do it that but this is an existing display drive. No chance to change this time..


Working too slow will have to recoded. I duplicated the same code for each display. Not very efficient but does debug the look up table. The display is dimmer because and can't get to the display routines fast enought.

interrupt [TIM0_OVF] void timer0_ovf_isr(void)
{
display_u18(u18_value);
display_u17(u17_value);
display_u10(u10_value);
display_u4(u4_value);
a_counter();
check_keypad();
TCNT0=255; /*set for 300us timeout Olimex 6mhz*/
}