New batch of pdp8 OMNIBUS to USB interface! Please Read and react!

Philipp Hachtmann hachti at
Wed Feb 15 10:13:18 CST 2017


On 02/15/2017 04:24 PM, Alan Hightower wrote:
> Perhaps I was unclear. It is not a direct port. It was inspired by your
> board during a road-trip to VCF-E to make an easier-to-assemble design.
Ah, ok.

> There is obviously no FT245 support. And just about any implementation
> of logic responding as a KL8E would look very similar. The code is
> available under MAIN.pld on the previous link.
Oh, I did not see that. No, that file has nothing to do with my source.
I have never seen that strange language. I only use VHDL (and verilog if 
I'm forced to) for logic descriptions... So this .pld looked like some 
binary for me. OK, I even didn't know that there are Atmel CPLDs.

> The design uses a UART and can be run up to 230 Kbps and tested up to
> 460 Kbps. It runs faster than the original hardware. The UART design
> certainly has limitations as you point out.

The speed does not matter. There it exactly one fault: The design uses 
an UART. The qualities or speed of the UART are irrelevant. But it's too 
slow, of course.

> But it is still an
> improvement on the original DEC serial hardware which most people still
> use.
> The design goals of this board are not the same as yours.
Probably :-)

I have to admit that I don't understand the design goal: Why should one 
*not* want to use a KL8<something> serial board? I like it very much and 
use some of them from 110 baud to 19200 baud.
I use them only as terminal connection.
So I see no use case for a however improved serial card - except when 
you don't have a KL8E. But that's a very theoretical assumption.

When I design something to be used with vintage hardware, I usually 
think of it as an addition instead of a replacement. I use OmniUSB IN 
ADDITION to KL8E. At the same time, of course. Console over KL8E, high 
speed data communication <-> PC over OmniUSB. I use it with Kermit, 
dumprest etc.
It's of course also possible to have several OmniUSB boards in the 
system :-)

  > It was designed to be easy to assemble without SMT. While I personally
> agree with your SMT comments, most people do have problems soldering
> .5mm pitch leaded components -

Yes, that's because they just did not try at all. They're stuck with the 
idea that they would have to solder the stuff pin by pin with a 
microscopic soldering tip. But I use a big reservoir tip. And then it's 
REALLY becoming easy! I also belonged to the fraction that thought it 
would be somehow impossible to solder TQFP and friends. Until I tried 
it. That was the day I started to forget about which THT components I 
could have laying around. With normal SMT and 0805 resistors I am 
completely happy.

> The ATF1508 was chosen after noticing it's data
> sheet revealed it could source the current requirements of the omnibus;
> a rare thing.
Yes, really.

> After your reaction, clearly... Look, no one is trying to step on toes.
I did not expect that. Don't worry! I just wanted point out how things 
in that area are handled properly.
I'm working in the software business and that kind of thought is part of 
my day job.
One should also be aware of the difference between public domain, open 
source, free software and the different license models and have an 
understanding of the applicable rights and obligations.

Kind regards


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