Panda Display USB support in klh10 working

David Griffith dave at
Sun Jan 3 15:06:53 CST 2016

On Mon, 4 Jan 2016, Mike Ross wrote:

> On Sun, Jan 3, 2016 at 8:43 PM, David Griffith <dave at> wrote:
>> I've managed to edit klh10 to talk to my new USB Panda Display
> *blinks*
> There's a USB Panda display?
> I bought two of the original parallel port Panda displays years ago.
> Recently wasted a lot of time trying to get them to work. The Windows
> diagnostic tool program works perfectly - sending patterns to lights
> and running them. But try to use them with klh and they initialize
> with a few random lights on when you start it and then never change at
> any point until *hardware* power is cycled. Evidently there's
> something screwy and the support for them was never actually
> incorporated into klh and/or the final Panda TOPS-20 release.

One of the big limitations of the original Panda Display is that the 
parallel port is accessed through IO ports, not the operating system. 
Because of that, a USB-to-parallel converter will not work.  I also got 
one of the original displays.  By the time I built it up, I didn't have 
easy access to a real parallel port.  That's when I started to design a 
USB-based display.  The hardware and firmware is fairly simple.  The klh10 
side of it is more complicated.

David Griffith
dave at

A: Because it fouls the order in which people normally read text.
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