That modified rex pcb and matching carrier I was working on are now at a
usable state.
There is a pcb which is REX1 electrically, with only some layout and
edge cut changes.
There is another pcb with the same outline that uses the same carrier,
but has only a simple eeprom on it. I'm calling that Teeprom.
There is a github with both the carrier 3d model and an empty template
version of the matching pcb, to make new circuits using the same pcb and
carrier. So hopefully this is reusable.
By now I have received and tested multiples of both pcbs and the
carrier, and everything is dialed-in pretty well finally.
I have several rex's and teeproms and a bunch of carriers all of the
current/latest versions the same as what's currently orderable on
oshpark and shapeways, and the boards all fit perfect in all the
carriers, and the carriers & boards all fit and work in my couple
M100's, T102, and T200.
I overhauled the build and flash directions a lot. Filled in more
deatails with actual steps as if going from scratch, expanded some steps
into their own separate docs but linked right where you need them. Could
still do more but it's just better than before. Simplified and organized
a little better (I hope).
http://tandy.wiki/REX
http://tandy.wiki/Teeprom
http://tandy.wiki/Pcb2molex8878
http://shpws.me/RngB
https://github.com/aljex/pcb2molex8878
https://photos.app.goo.gl/zynHU4LSpd5BZBYC9
I'll get the rex and teeprom full sources up in a github or something
soon too. The .kicad_pcb files are already available via oshpark, but
you want the rest of the kicad files too if you were going to work on them.
Anyway, it's at the point now where I'm saying it's ok to order these
things and they'll work and I'm not still changing them and obsoleting
them right after you ordered them.
Just for the record, I have the shapeway shop set at 0% markup for all
the items. I don't want any damned shop but that's just the only way you
can share the model on shapeways so that other people can order prints
without downloading and uploading the mesh files themselves. The same
model is also on thingiverse where you can share without having a shop,
but thingiverse is mostly FDM printers, and I don't think any fdm
printers are good enough for this part. But, if you have your own
printer and want to try it, the mesh file is up there. So the only
reason there is a "shop" on shapeways is just to get shapeways laser
sintered nylon printing. It comes out very clean and accurate and strong
enough that the part is actually usable.
You may notice that the seemingly nicer print options are not enabled
for this on shapeways. That's on purpose. If you get the part printed in
multijet fusion, it looks great, but doesn't fit.
Unfortunately, for the carrier, my freecad "source" file, while
available in the github, isn't actually very "source"-like. It's
essentially just the final 3d solid shape just like the stl file for
printing, not all the steps to build it up, nor any parametrics you can
edit. But I do plan to redraw it from scratch in freecad or better yet
openscad sometime. Especially openscad will make it awesome for keeping
in git.
Also if you wanted, it IS actually possible to modify a standard REX to
go in one of these carriers.
You would do 4 things:
1: Cut the polarity pin off the carrier. Doesn't have to be any more
accurate than just lower than the lip on the bottom tray. Just use wire
cutters or a knife.
2: Sand both ends of the pcb (the two short dimensions) down about 0.5mm
each, or whatever it takes until the overall length is 37.35mm or
shorter, and doing both ends equally. This will eat into the jtag pin
holes a little, but actually not enough to hurt anything. You could even
still use the jtag port if you ever needed to. It doesn't affect normal
operation at all.
3: Chamfer all 4 corners of the pcb edge about 1mm each corner. Make the
very ends narrow enough to get between the vertical walls on the ends of
the carrier, yet don't chew into the edge contacts at pins 1, 15, 15, 28
more than about 10-20%. You can actually graze the ends of those 4
corner contacts slightly and they'll still make perfectly good contact.
But you should be able to just barely not touch the actual half-circle
part.
4: Remove anything glued to the bottom of the pcb. Some glue residue
left behind would be ok on the pcb surface next to the flash chip, up to
the thickness of the flash chip, but the surface of the flash chip
should have nothing thicker than paper on it.
--
bkw
On 7/29/19 9:34 AM, Josh Malone wrote:
Fred,
If this is one of my REX units (shipped with wood spacer and a purple
polka-dot ribbon) then my apologies for your issues. I tested the
spacer sizing in 100, 102, and 200 units and found what seemed like
the right size to prevent over-insertion and "spontaneous removal".
I'd have to check my notes, but I sanded my boards down to a precise
size which I think was 0.048" (~1.2mm). They do require a very firm
insertion into the socket -- you may feel uncomfortable applying that
much force -- but you should feel the board snap into place below the
catch in the pins. If you don't feel a "snap" then it is possible that
the spacer board is too thick for whatever reason. I don't use any
adhesive, etc. on my boards to make it easier to repair them should
anything go wrong, but I've also had one other issue with a user
neglecting to install the spacer which caused damage to the REX and
his M100, so I will be changing to adhesive spacers on my next batch
(which I'm producing the Tandy Assembly).
When you install REX, do you feel it snap into place? Can you send
pictures of the installed REX? (You'll have to find a host for them
since the list doesn't handle attachments; or send them directly to
me)
Brian's work with the new REX PCB and the 3D-printed carrier looks
neat -- I'm following his progress -- so if you continue to have fit
issues one of those carriers might solve your problem, as well.
https://photos.app.goo.gl/aNfjvB1XucSehPGB9
-Josh
On Sat, Jul 27, 2019 at 8:29 PM Stephen Adolph <[email protected]> wrote:
Hi Fred,
Honestly my first thought here is ... what software are you running and have
you ever done a total wipe of rex followed by a reload from scratch of the
software?
These symptoms more or less sound like corruption of the directory which can
happen on older software loads.
I've tried to catch all the fixes in my last supported software load. Which is
at bitchin100.
..Steve
On Saturday, July 27, 2019, Fred Whitaker <[email protected]> wrote:
I have been having trouble with my REX chip becoming loose and losing data as a
result. The computer also locks up. I was wondering if anyone had any ideas
about better support for the chip corners, instead of a loose piece of wood
under it.
I was thinking of trying to find some small diameter thin stick on feet, about
1/8 inch thick. Has anyone had a similar problem?
The problem will be the same with any of the ROM's on similar boards. The Super
ROM that I have is on a similar board but it also has a full length spacer
glued to the bottom of the board.
Until I can resolve this issue I am putting my REX chips in storage. This is
only true for the Model 100 and Model 102.
