One of my zillions of projects is to redesign Oscar Vermilion's PdDP-8/I
using the Raspberry Pi Pico board and these LEDs.
I would use one core for SIMH (the PDP-8 simulator) and one core for the
Incandescent Emulation.
Right now I'm too busy finding parts for my real PDP-8/E and getting it
running.
Think of the addressable LEDs and LEDs with the shift register built in 😄.
When you are ready for a redesign, you might consider it for a cost
reduction.
If I may8 ask a question. I have never had boards made before. How do I
find a good board house that is reasonable and how do I specify the
board especially for the PDP-8 Omnibus which should have gold fingers on
the edge connectors?
Thanks and good luck,
                 Mike
On 12/6/2021 2:07 PM, David Bridgham via cctalk wrote:
On 12/6/21 10:36 AM, Mike Katz via cctalk wrote:
Each LED requires 24 bits of data. That would be 3,456 bits. The
WS2812B has a 300uS low start indication and 1.25 uS per bit. That
would mean it would take. 4.62mS to update the all of the LEDs.
If I'd known about those when I designed my boards, I might well have
gone that way. They're surprisingly inexpensive even.
Instead, I ended up using a 16-LED driver chip that basically looks like
a shift-register. I clock in the 144 bits (just on-off, no fancy
tri-color LEDs I'm afraid), toggle the latch signal, and there it is.
If you want to support more indicator panels, it's just a longer shift
register. I then added RS422 driver chips for noise immunity and there
I was.
Dave
