[CLUG-tech] 'tis the season

Bernd Jendrissek bernd.jendrissek at rocketseed.com
Mon Dec 10 11:08:16 SAST 2007

Jonathan Carter (highvoltage) wrote:
> Hmm, this is clug-tech and there's no Linux in that solution. Perhaps he 
> should control the two sets of lights from two serial ports instead? 
> (and perhaps even power it from there too?)
The serial port drive capability is rather limited, and you'd have only 
two signals you could frob at dc-like frequency: RTS and DTR, IIRC.

You could get a bit more out of a parallel port, with 8 output lines, 
although there too you'd have to watch the drive capability of the port. 
Each LED sucks about 20mA.

Then again, if you power your LEDs from your USB port, there will be 
oodles of power at a convenient 5V. Hook up a serial converter chip and 
use RTS/DTR as clock and data lines of a bit-bashing I2C interface.

Implementation left as an exercise to the reader

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