Shop OBEX P1 Docs P2 Docs Learn Events
Not enough pins - multiple 7-segment displays — Parallax Forums

Not enough pins - multiple 7-segment displays

Electrically ChallengedElectrically Challenged Posts: 22
edited 2012-05-27 08:58 in Learn with BlocklyProp
So, I've got a project rolling around in my head using multiple 7-segment displays (8 total). Instantly, I see that there is no way I'm going to have enough pins... I'm wanting to display binary code mirroring the 00010010 digits that we use for the 7-segment displays. Is there an end around? The displays don't have to come on all at once - they could come on sequentially.

I'm just starting to learn the microcontroller so obvious answers won't be evident to me.

I've seen multiple displays (four sets of 7-segment displays), but not interested in those. I'm wanting them individually placed.

Thanks in advance,

EC

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2012-05-26 20:42
    Something like this decoder-driver chip will do all the interfacing for you and only require 9 I/O pins, 8 of which can be shared with other functions. You could also use something like a 74HC595 serial shift register per display. There are decoder-driver chips that use serial I/O and fewer I/O pins, but you'd have to look at Maxim/Dallas' website to find one.
  • Electrically ChallengedElectrically Challenged Posts: 22
    edited 2012-05-27 04:39
    Thank you. Will look into this. Surprised you are working on a weekend - and a Memorial Day weekend at that!

    EC
  • Mike GreenMike Green Posts: 23,101
    edited 2012-05-27 08:12
    Here's the serially interfaced version. It needs only 3 or 4 I/O pins for interfacing. You'd use SHIFTIN and SHIFTOUT to transfer the data in and out.

    Like most of the "experts" here, I'm a volunteer. I don't work for Parallax. I have spare time in bits and pieces, often in front of a computer, which is ideal for this sort of thing.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-05-27 08:58
    I'll second Mike's suggestion of a 74HC595 shift register.

    I haven't used the Maxim chips Mike also suggested so I don't know how they compare in ease of use (but from the datasheet, the Maxim chips don't look simple to use).

    I personally think the 595 is pretty straight forward to use. Even if you don't use a 595 in this project, they're a great chip to have on hand since they are so useful.

    Here's link to a LED project I made using sixteen 74HC595 chips. I almost forgot, I also have a 7-segment project here.
Sign In or Register to comment.