7-segment display with P16F84

[hoops2006]

Does anyone know where i can get one of those 3 digit seven segment displays that are designed to be multiplexed. aka has 12 pins instead of well loads more.

[hoops2006]

quick one.
in the 7 seg display program what does ~dcd mean in the line
digits=~dcd i
thanks

[spitfire]

quick one.
in the 7 seg display program what does ~dcd mean in the line
digits=~dcd i
thanks

~ = NOT
and
DCD = it changes a bit number (0-15) into binary and set that bit to a Logic 1

Basicly it finds out what value digits is (0 to 3, 0 being the first display on the right and so on) and converts that into binary if 0 then to 00, if 1 then to 01, if 2 - 10, if 3 - 11 and instead of applying a logic 1 like DCD is supposed to do it does the opposite because there is ~ infront of it which make it 0

Its basicly applying a Logic 0 to pin RA0 on the PIC,completing the subroutine and then doing the same for pin RA1, RA2 and RA3. These are the pins that turn on and off each digit.
Logic 0 normally means 0 or close to 0 Volts but in this case transisors are being used to supply the current to the display. A transistor is basicly an inverting switch so if you input logic 1 (+5V) you get 0 at the output and the opposite if you apply 0 Volts to the input.

I got a little carried away there and have gone into more detail and answering more than you asked but it might help you understand what the code is doing a bit better. Or atleast I hope so.

[hoops2006]

Many thanks for your reply spitefire just what i needed. I made a boxing round timer a while back, now im trying to improve it by displaying the time on a 7 seg display. its proving to be tricker than i thought. As im still struggling to get my head round this one as im a newbie to pics your extra info helped alot.

[spitfire]

No worries hoops, nice project there. Have you got the hardware side finished yet?

I'm also somewhat of a newbie to PICs but after studying discrete logic and designing a 24 hour clock with cmos 4000 series IC's (made my own 4 digit 7-segment display on veroboard using 58 blue LEDs) I now unterstand abit better.

I'm interested to see how it turns out.

[hoops2006]

Yes i think i have a fair idea of the hard ware. Pretty much the same set up as the link you gave on the first post. Two microswitches for round selection .With a relay chunked in for the buzzer. But my objective for now is to get minutes and seconds counting down on the display. Once i have that ill start worrying about how to select the times i want ect,

So i have plenty to keep me going. ill keep you posted.

[hoops2006]

Would a count down timer be as simple as:

for sec=59 to 0
pause 1000
if sec=0
then minutes=minutes-1
gosub display.

the value for display would be (minutes*100)+sec eg if 3mins 59 sec value 359
then just display the value as per the code on the link.