1 Jul
2006
1 Jul
'06
2:45 p.m.
On 7/1/2006 at 10:00 PM Philip Pemberton wrote:
And I doubt the parallel port would be fast enough.
Jules didn't mention how many charcters he wanted to display, nor the
length of persistence of the phosphor on his scope, nor the quality of the
characters (i.e. are line segments good enough or does one have to do a
true arc rendering?), so I've got to wonder what "fast enough" is? Even on
a 486, punping out 100K bytes/second through a parallel port shouldn't be
much of a problem. Build a table of datapoints for the whole display and
loop right through them.
Heck, the simplest DAC is a bank of 20 resistors (R-2R
ladder). Cheap too
- a penny a resistor, total cost of 20 British New Pence. I don't think
ADI or
Maxim have anything cheaper...
Hmmm, I thought I said that!
If you had two parallel ports, you could save some
money at the expense of
accuracy, by using a simple resistive ladder DAC:
http://www.epanorama.net/circuits/dacs.html
An item I hadn't though of, though, is that you may want to save a bit for
blanking the display between characters.
Cheers,
Chuck