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

[David Kelly]

On Wed, Feb 27, 2008 at 12:35:57AM -0800, 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.

Faced with a similar design problem recently my solution was to use
individual 8 segment (8th is decimal point) LED modules and drive each
with an Allegro A6278. Daisy chain the serial data out from one to the
serial data in on the next, and shift 24 bits out the SPI, then toggle
the data latch.

This particular design had a unique requirement in that when inactive
there shall be no oscillators running. That includes multiplexed LED
drivers.

A nice feature of the A6278 is the active drive current regulation. One
resistor sets the drive levels for all 8 outputs.

Used more A6278's to drive optocouplers in other parts of the design.
They are not dirt cheap, they are not terribly expensive, but they
worked first time without a hitch.

-- 
David Kelly N4HHE, address@hidden
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Whom computers would destroy, they must first drive mad.