connect 4 7-segment to PIC 16F877A with min. ports no.

[h.d]

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 ​

 

[weegee]

(assuming you mean led's)

people will be getting bored with me saying this, but... ---> Max7219, will handle up to eight 7seg leds, and will use just 3 pins on your pic.

they can be cascaded, without using any additional lines on your pic too, so two max7219's cascaded will do what you want using only 3 i/o pins.

https://www.electro-tech-online.com/custompdfs/2008/01/MAX7219-MAX7221.pdf

 

[kchriste]

How many IO pins do you have free for the x4 7-segment displays?

 

[h.d]

I need 3 inputs forsensors
and one for PWM
and i should add 2 push buttons to increase and decrease the speed

 

[blueroomelectronics]

You only need 11 I/O at the most for a 4 digit seven segment multiplexed display.

 

[h.d]

You only need 11 I/O at the most for a 4 digit seven segment multiplexed display.

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?

 

[kchriste]

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**

 

[blueroomelectronics]

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.

 

[h.d]

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.

i should show the four variables in the same time
can i do that on LCD?

 

[blueroomelectronics]

Sure, why not. LCDs vary from 8x1 to 40x4 and larger.
16x2 is common and cheap
**broken link removed**
A great big 40x4 display

 

[futz]

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.

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.

On the other hand, LCDs are dead simple too.

 

[blueroomelectronics]

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.

 

[h.d]

thanks for all replays