Building a REX

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Introduction

Building a REX, BKW version.
This is essentially a REX1 with a modified pcb layout from Steven Adolph's original.
Electronically identical.
Software identical.
PCB shaped to snap into a 3d-printed carrier, and provide connections for power and PORT_EN for programming the CPLD.

Original version of this page, for building the original REX1

Parts & Materials

• PCB: https://oshpark.com/shared_projects/DKF7eN1c
• BOM: https://www.digikey.com/short/pbn7vw
• Sled: http://shpws.me/RngB

Other Compatible Flash Chips and how to identify them

Tools

• Cheap clone Xilinx Platform USB programmer.

https://www.ebay.com/sch/i.html?_nkw=xilinx+usb&_sop=15

Look at the pictures for ones that say model DLC9G preferrably, or DLC9LP. Don't put "DLC9G" or "DLC9LP" in the search, you will only get the overpriced ones.

Get one that includes a "flying leads" cable, with separate loose individual wires on one end.

• 3.3v-5v power source

https://www.ebay.com/sch/i.html?_nkw=usb+ttl+cable&_sop=15

These usb-ttl cables are perfect, in that they are cheap, and already have loose wires with female dupont pins.

Just use the red and black wires and ignore the rest.

• PC with at least one usb port, and a COM port or usb-serial adapter.

• Sandpaper, medium grit (120 or so), and a hard flat surface like a cutting board.

• Soldering Iron

Do not necessarily need anything fancy. I actually used this exact one to build a few REXs, although now I use a Hakko FX-888D.

• Solder, fine pitch, 63/37, no-clean flux or rosin core

• No-Clean Flux

• Mini Vise

• Magnifying Glasses

Or the strongest reading glasses you can get at a local drug store. 3.00x or higher.

• Alcohol for cleaning up

Don't really need this. The "no-clean" flux above could be left on, or cleaned with warm water.

• Tweezers

• Single-Row pin header

..and a single shunt.

0.1" (2.54mm) pitch

You only need 10 pins. Break off a section of 6 pins, and a section of 4 pins.

• A Tandy Model 100, 102, or 200.

• A 9F-25M-Null-Modem Serial Cable

Prep the PCB

Lay a piece of medium grit (100-200) sandpaper face up on a hard flat surface like a cutting board.

Sand the edges of the PCB on the sandpaper just enough to clean off the panelization break-away points.

Use magnification to look closely at the castellated edge contacts for copper or gold "flags" hanging on the edge of most contacts. Scrape them off with and xacto knife.

Assembly

Electronic Components

Solder these parts onto the matching labeled locations on the pcb.

U1 = XCR3064XL

U2 = 29F800 (on the back side)

U3 = LP2980

R1 = 10K ohm

C1 = 1.0 uF

TP1 & TP2 = right-angle pin (optional)

Don't be too intimidated by the tiny legs on that TSOP-48 chip.
Just use magnifying glasses, lots of flux, and the DRAG TECHNIQUE.
Another example: https://youtu.be/09qb0KY_IF4

The TP1 and TP2 pins are only needed if you think you will ever perform the hardware modification required to use the main rom management feature.

Clean

Even "No-Clean" flux should still be removed as much as possible after soldering. But without an ultrasonic cleaner, it is just about impossible to get the flux cleaned out from under the chips. So, using no-clean just means the flux that inevitably isn't removed, won't be too harmful. Use 99% isopropyl alcohol and a small paint brush to wash the flux off.

Programming

There are two parts to program, the CPLD and the firmware.
The CPLD is done with a Xilinx usb programmer via the jtag pin header.
The firmware is done using the Model 100 connected to a modern pc by serial cable.

Program the CPLD

Now we need to flash the CPLD (Xilinx) with the .jed file. This configures the blank CPLD into a functional circuit that actually does something.

• Get the .jed file from here.

• Install Xilinx "ISE 14.7 Lab Tools"

Directions for Ubuntu Linux

• Connect the jtag, 5vdc, and PORT_EN jumper.

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• Use iMPACT to program the .jed file

Carrier

Place the end of the PCB without the hole into the carrier first, then snap the rest of it in.

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Flash the Firmware

Install the REX into a Model 100, 102, or 200.

Follow the 4.9 update directions to load the firmware.

The directions for the 4.9 update state that you use any tpdd device to serve the 3 files to the M100/T102/T200, but in fact at least at present, it does not work with actual tpdd1 or tpdd2 drives at all, and is not reliable with just any tpdd server either. You must use specifically LaddieAlpha.

TODO: Document this part better. This is a bullet list, but there are more details involved for each item in order to actually do them.

• Get a proper serial cable
• Install a TPDD client on the M100/T102/T200: Any, teeny, floppy, ts-dos. If you don't have anything already, then get the "dlplus" zip file and run the teeny installer that comes with it.
• Get LaddieAlpha onto a PC.
• Get the 3 update files.
• Run LaddieAlpha in the dir with the 3 update files.
• Use whatever TPDD client you installed on the M100 to copy rf149.co to the M100.
• Run rf149.co on the M100.

Until this part of the directions is improved, there are several pictures of the full process here: https://photos.app.goo.gl/aNfjvB1XucSehPGB9

Done!

That was the last step. You're done! Consult the REX docs to start using it!

References

Version c6 pcb, pcb is obsolete, but has pics of the Firmware flash process

Version c8 pcb, more pics of building the current version

User Manual

Original sources and support files

Copies of some of the sources and support files, and new sources for some things modified from the originals