> Exactly, I'll multiplex them one LED at a time

The 'normal' way would be to strobe whole columns, as in the
4-digit schematic I sent a link to

There are two things to consider - light output and persistence
of vision

Essentially you have a 14 x 6 matrix of LEDs. For a static display
I don't think that is much of a problem, timing-wise at least

To slightly digress, the moving sign I built is 64 columns refreshed
at 200Hz and scrolling on that looks quite smooth. Admitedly it is
smaller, using 3mm LEDs, than all-purpose commercial units, but
the principle is the same. You will often see poorly-designed units
where a too-low refresh rate causes the display to 'lean'. This will
happen especially when the display is too long for one micro and
the time delay to get from column1 to columnX causes spatial
effects. For mine, each of 64 columns is refreshed 3 times per sec
at an overall 200Hz trobe rate, which at the moment is adequate

If you choose to make the columns 14 LEDs high, gettting their
'high-side' data and current straight from the PIC, then you need
only 6 column drivers, which simplifies strobing considerably

Your unit does not have a need for scrolling, although there's no
reason why you can't add special effects like star-bursts or all
the tiles falling down at the end of a game. Once this driver issue
has been sorted out that's all in s/w anyway

Another time strobing is seen is when an LED is driven by AC,
perhaps from the front end of a PSU. Moving your head with the
LED in your peripheral vision will make the mains frequency, for
example, apparent. However, looked at front on you would not
be able to tell. It does indicate though that 50Hz is too slow for
steady illumination

The PIC can appear to be as busy as you choose it to be, but it's
basically doing very little. A timer or WDT interrupt to check for
buttons, format new data, strobe the column drivers. That's about
it. In between it can be asleep. Data and column selection is on
the port pins during sleep, so there's no need to be awake

Now, no matter what frequency you use, each LED is going to
get only a fixed time slice - (100/6)%. In that time, you have to
supply enough power to the LED for it to light effectively. If you
used the same resistor as you would for static display, the bright-
ness at 16% duty-cycle is obviously going to go down. So the
resistor is reduced accordingly. The determining parameter is the
LED wattage/peak repetitve current rating. And you'll have to
find that in the datasheet of the LED you choose

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