Re: [avr-chat] ATmega88 + triple 7 Segment Display (CC)

[Paul Lowe]

Here's one way to do it (thought up by a Comp. E. student who thinks
he knows everything):

Otherwise, here is a solution using only one data port in parallel:

- Wire each 7 segment display to a digital 8 bit latch.
- Use one data port to send your seven bits of segment data to all
three seven segments via a bus
- Use two wires as multiplexing selection lines to select which seven
segment latch will receive the data. (e.g.: [00] -> segment 1, [01] ->
segment 2, [10] -> segment 3)
- Use some digital logic chips to check the multiplex selection lines
to see which digital latch to enable for loading.

So:

       7-bit Data line
    (to all three displays)

_____                      |-----[Latch 1]---[7-Seg-LED-1]
|AVR|----------------------|-----[Latch 2]---[7-Seg-LED-2]
|   |                      |-----[Latch 3]---[7-Seg-LED-3]
|   |                                |
|   |      2-bit Selection Lines     |
-------------------------------------|
        (goes to all three latches)

Or, if you can only use one pin for data transfer, get a SPI external
register chip -- and map the output of that chip to seven output pins.

Cheers,

-Paul Lowe


Student1 wrote:
> Hi,
> I've completed a circuit for an ATmega88 that is to be programmed through
> Serial Port. I've tested it with LED and now I want to hook up a triple 7
> segment display (common cathode) to give it a 10 minute counter. 000 to 959
> (before resetting).
> 
> So my question is, now that I have purchased a 7 segment CC, how do I do the
> circuitry to attach it to the AVR properly. From what I have seen, a single
> 7 segment display has 10 inputs (2x GND, A->G, dp). My triple 7 segment
> displays has 11 pins on it.
> 
> And from looking at the ATmega88 specs sheets, it has 6 PORTB, 6 PORTC, 8
> PORTD which I can use for programming. Although PORTB0 is for input capture
> for timer/counter (what does this mean?). 
>  
> [img]http://img120.imageshack.us/img120/2598/img0820kf7.jpg[/img]
> http://img120.imageshack.us/img120/2598/img0820kf7.jpg
> [img]http://img101.imageshack.us/img101/892/img0822ot6.jpg[/img]
> http://img101.imageshack.us/img101/892/img0822ot6.jpg
> 
> After I get this done, the next part will be working on the programming.
> Hopefully a lot of the capabilities from the delay program will work for
> this one.
> 
> Thanks
> 
> Maybe I should add the 7 Segment CC P/N is LEDSM-314220 (although an online
> search turned up nothing). It says RGE30361LP on the side as well.
> 
> On the back 6 pins at top and 5 points at bottom.
> 
>