Driving 7 Segment Display with Microchip 8 Bit Controllers

[Steve NA]

Hi, I'm currently driving 7 segment LED displays using the A/D input.
The displays work well, but because the A/D input has a minor amount of ripple (a few millivolts),
there's chatter or a ghosting between segments.
I have tried to minimize the ripple, and was wondering if there's something in code that can stop this.
I'm a novice and work only with assembly at this point.

Thanks, Steve.

 

[Joe G]

the ghosting in the segments would most likly be caused by to fast a refresh rate, try clearing the display when updating them, as in: clear PORTB, move UPDATED code to PORTB.

 

[Steve NA]

Thanks for your comment. I had tried changing the clock frequency previously, but it didn't seem to help.
I can now see how clearing the Port will help.

Thanks again.

 

[dr pepper]

As Joe says before switching commons on the dispaly turn all the segments off, or this will happen.
If your confident this isnt the case, try taking say 8 measurements over equal amounts of time, then add them together and divide by 8 to get an average, this should smoothen out the display, as long as the input doesnt vary wildly.
Dividing by 8 is simple enough just shift right 3 times.

 

[magvitron]

You can

1. Average value over a fixed number of sample
2. add a delay after displaying a character.