hi all,
i want to connect 4 7-segment display to PIC 16F877A
the 1st is 4 digit
the 2nd is 3 digit
the 3rd is 3 digits
the 4th is 2 digits
and i want to use the minimum number of ports beacause i need it to connect sensors and the PWM port to motor
so i tray to do that with one PIC
is it could>? and how?
thanks
ok i know that
but i have 4 displayes
one of them is 4 digit the 2nd &3rd is 3 digit and the 4th is 2 digits
how many pins i need to connect that no. of diplayes?
So that's a total of 12 digits then. So 8 + 12 = 20 IO pins if you do it the traditional multiplexing way. If you want to use fewer pins look into charlieplexing: **broken link removed**
And you could also do it with a shift register or a pair of CD4022s. That 1:12 mux is going to need HE RED displays or it'll be really dim.
Might be easier to use an LCD instead.
And you could also do it with a shift register or a pair of CD4022s. That 1:12 mux is going to need HE RED displays or it'll be really dim.
Might be easier to use an LCD instead.
CD4022s are nice and easy to use, and cheap. I've got the one on my Dragonfly all figured out with nice timer interrupt multiplexing and display management code now.
I used the CD4022 mostly because it's impossible to turn on more than one digit at a time and only takes two I/O (plus it active high so I could use NPN drivers). Seemed like more fun than a 74LS138 with its active low outputs, or more fool-proof than a shift register where you can turn on ALL the digits by mistake.