On 2/26/23 08:23, Stephen Adolph wrote:
Brian, If I understand your comment, I don't think you need an IC to do
rom selection. I think the DAR uses a rotary encoder.
I understand that the dar uses a rotary encoder.
The slide switch needs the extra glue.
I was responding to Mike's question "how does the bank select work?"
answer: gratuitous extra parts because I just wanted a slide switch.
When I first saw the DAR, I wondered about that. I'm pretty sure I found
the part at Digikey. Very good!
Steve
On Sun, Feb 26, 2023 at 3:51 AM Brian White <[email protected]
<mailto:[email protected]>> wrote:
Gratuitous use of another chip just for 2 OR gates to implement a
4:2 encoder. It's all less efficient and less practical than the
dial-a-rom, in that the dar holds 16 roms and doesn't need another
ic, and the dar programming connection is even simpler and more robust.
But it just amused me to have a direct selector without manually
binary encoding dip switches because why not? And I didn't want it
to require a tool to use either like a screwdriver. And of course I
always want an open source option, and I'm not up to the task of
coming up with an open source rex-alike but using a Lattice part and
the open source toolchain.
It's unfortunate timing but I had already started this at least 3
years ago but just never finished it. A non-working version has been
sitting in that github since 2019. A few weeks ago I finally dusted
it off and corrected my bonehead pinout error, dialled-in the
programming connection so it works well (the holes are slightly
closer together than the pins, and the pattern and amount of offset
took some trial & error) and replaced dip switches with the slide
switch & or gates. I had no idea the dar was in the works. Not that
it would have stopped me, but I just mean to say this isn't a reaction.
It's no competition anyway because only a very few people ever build
these diy-only things. I want them to exist so the option is there,
but almost no one actually employs it. So this is not touching
anyone's sales. Besides, *16* roms. And of course really it's even
sillier when rex exists which doesn't even need a programmer or
adapter to load it's, what, 30? slots? But for other platforms 4 is
plenty. There's only 2 roms total for the 600 for example. Still
leaves 2 free slots for hacking.
I just added the browser-friendly render of the schematic to the
readme so you can see the bank-select.
--
bkw
On Sat, Feb 25, 2023, 8:18 PM Mike Stein <[email protected]
<mailto:[email protected]>> wrote:
How do you select among the 4 images?
On Sat, Feb 25, 2023 at 6:50 PM Brian K. White
<[email protected] <mailto:[email protected]>> wrote:
On 2/25/23 10:31, [email protected]
<mailto:[email protected]> wrote:
> Morning all,
>
> I just made this video live this AM. The DARs for the
Model T computers
> have sold out already but my friend is making more.
>
> In this video we take a look at the ‘Dial-A-ROM’ a spiffy
new multi-ROM
> for vintage portable computers. It was designed by the
same guy who did
> the Backpack drive. First, we’ll learn how to use the
Dial-A-ROM with
> the ROM images that come preinstalled on it. Then we’ll
see how to add
> our own ROM images if we so desire.
>
> *https://youtu.be/CejyLsI0HIw
<https://youtu.be/CejyLsI0HIw> <https://youtu.be/CejyLsI0HIw
<https://youtu.be/CejyLsI0HIw>>
>
> Jeff Birt (Hey Birt!)*
>
And for the diy-er, I finally vetted these last week:
https://github.com/bkw777/Teeprom/blob/master/4ROM.md
<https://github.com/bkw777/Teeprom/blob/master/4ROM.md>
--
bkw
--
bkw
