Is it worth trying to come up with some surgery bodge procedure to
upgrade a 256K unit to 512?
It's a very small change and although there is an added part and it's
tiny and not easy to solder wires to, it's probably actually possible to
cut a few traces and add the new part with fine wire-wrap wire and glue
it all down.
I think the new part (LVC1G79) can even be soldered to the board pretty
much right where it is on the new board instead of dead-bug, because two
of the pins are VBUS & GND, and they are on opposite corners of the
package, and both are available on the pcb in the right spots already
just by scratching the soldermask pretty much right where the part goes
on the now board. Angled a little but hey whatever. So that not only
connects 2 of the 5 pins, it mounts the part as if there were a footprint.
Two more pins have short easy bodge wire runs to nearby exposed pins
with no need to cut any traces or anything. Those are /BLOCK and
BUS_A10. Pin 1 goes over to connector pin 16 and pin 2 goes over to U4
pin 14. Just add the wires to existing exposed legs, no cutting traces
or lifting legs.
That just leaves pin 4 A18, which needs a trace cut on the back side of
the board, and a wire run from pin 4 to sram pin 6. The trace to cut is
the one that ends with a via right in the D in NODE on the back side,
it's a thin trace that runs down towards the connector, and transitions
to a fat trace before going under the connector. Break the thin section,
do not break the fat section.
And actually since we're not soldering to a footprint, you can buy a
larger package version of the part so the lags are a easy to solder
wires to. It's available in SOT-23-5/SOT-753/SC-74A which should be dead
easy.
Ok well I guess I just did the thing I was asking if it was worth doing.
But, it's probably not much worse or maybe even easier to just
transplant all the parts from a built 256k to a new 512k board. That's
what I did. I didn't bother with the caps or resistors but all the chips
I desoldered with chipquick, cleaned the low-melt off with wick, and
soldered to the new board.
In one sense it's silly to spend that much time on parts that add up to
a couple bucks, your time is worth more, but on the other hand if you
didn't buy 100 of each part and you've built a few along the way
developing... it's hard to look at a board full of parts and just toss
it rather than scavenge the parts. The math does not justify it at all
since I'm not broke, plus the chipquick and kimwipes and flux-off isn't
free, but I just can not make myself not scavenge those parts!
My REX Classic is on revision 30 or so by now, and I have 3 or 4 rexs
that have had their chips transplanted like 10 times, and so far
everything has seemed to survive all that accumulated solder hot time
and ultrasonic cleaner time. Everything is still working anyway.
--
bkw
On 12/13/23 16:34, Brian Brindle wrote:
Haha - Glad you like it Joshua if I do happen to make more or improve on
this one I'll let you know. I don't exactly have ADD but what I do seem
to have is the inability to control what my current interests are and
recently it's been playing with CP/M on the M100, PX-8 and building up a
CP/M emulation environment on the TanPi. That was going great till I
managed to get my hands on one of the MiniNDPs Brian K White made and
now I'm all about his recent 512K upgrade. Never thought I'd get to play
with an NDP so this is exciting stuff.
I have a WP-2 and have tried to use the TanPi on it, but usually ended
up frustrated with the lack of needed keys. When doing unixy stuff
having pipes, curly braces, back ticks etc are handy. The M100 seems to
have everything I need, although you do have to know to hit shift GRPH -
to do a pipe and GRPH ( for { etc.
I like ROM-View 80 but for me it's not enough of a payoff to have to
reconfigure the local terminal settings to accommodate the new layout.
The way I use the TanPi is primarily for content creation and syncing. I
will write documents either with a real editor or just by typing cat >
file.txt and typing away with CTRL-C to stop. Then sync the files with
my local storage or the cloud when I have WiFi. If I need to do
something really heavy I'll use an external screen or my VNC session
with my phone.
A lot of times when I'm at home I will ssh into my TanPi from my desktop
and can drag/drop files over SSH, use the real keyboard and monitor for
stuff and it's quite handy.
It's a fun toy.
Brian
On Wed, Dec 13, 2023 at 1:29 PM Joshua O'Keefe <maj...@nachomountain.com
<mailto:maj...@nachomountain.com>> wrote:
> On Dec 13, 2023, at 6:22 AM, Brian Brindle <bbrin...@gmail.com
<mailto:bbrin...@gmail.com>> wrote:
> My whole setup is a total kludge / hack that I never expected to
use long term. I was just doing a POC and built the whole thing in
about 10 minutes with stuff I had laying around but here we are
almost five years later...
Brian, you may consider this rig a kludge, but I'm jealous and think
it's gorgeous. Using the T as a portable terminal with a perfectly
capable tiny Linux box cleverly attached is a great hack. I wish I
had one of these! A 9-pin WP-2 version—what with the 80-column
display—would be amazing.
Now that I think about it, have you tried using either one of the
80-column software setups, like ROM-View 80 or Ultrascreen100? It
might make for an even more pleasant terminal experience.
Gosh, I'm tempted to ask if you'd slap another one together in your
copious free time!
--
bkw
