WiFi CoCo for $15 (or for any retro computer with an RS-232 port)

Updates:

  • 2018-02-04: Removed an apparently necessary step.
  • 2018-02-05: Added crude drawing showing how I wired things up.

If you want to get your Tandy / Radio Shack Color Computer (CoCo) on the internet (or any other 80s computer with a serial port), here is a dirt cheap way you can do it.

Cheap WiFi: The Early Years

Just a few years ago, adding WiFi to an Arduino meant buying a $60 add-on. My solution at the time was to get a much cheaper Ethernet and then use a cheap TP-LINK WiFi router hooked to it. I later found a source for a $10 Ethernet shield that made the overall cost even lower.

In 2014, the internet lit up with the discovery of the ESP8266 – a complete “WiFi on a chip” solution for under $5! Initially, all documentation was in Chinese but folks managed to figure out how to use it and, as they say, the rest is history.

Today the ESP8266 family of products is used in all kinds of things. There are now internet-enabled light switches, and front-ends for 3-D printers, and many other devices that get online thanks to this low-cost solution.

And, this includes all these retro computing platforms!

Cheap WiFi: How To

If you want to experiment, you can order an ESP8266 development board from Amazon for $8.79. This contains the low-cost ESP8266 module and then runs out all the various connection to pins, and also has a USB-Serial adapter built in. This USB port allows you to plug it up to a Mac or PC and upload new firmware, or use the device directly through a serial connection.

Here is the module I purchased. You can find many variations, some costing more, and others costing less. I wanted one I could get direct from Amazon using 2-day Prime delivery, but if you don’t mind waiting, you can find a similar part shipped from China for about $4.

An ESP8266 development board, available for under $9 from Amazon. (And much less from China!)

Since my 1980s computers do not have a USB port, I needed a way to hook them up to the old-style RS232 serial port instead. For that, I bought a cheap RS232-to-TTL adapter. Here is the one I purchased for around $7, shipped from Amazon with 2-day Prime shipping. I see there are some for a few bucks less which might work just as well, and if you don’t mind waiting a few weeks to get something shipped from China, I have seen them for about .67 cents!

RS232-to-TTL adapter.

Now all I had to do was connect the two modules together using some jumper wires. I needed four wires to connect Voltage (mine needed 5v), Ground, Transmit and Receive. You can buy a bundle of these wires for just a few dollars.

Once connected, it looked like this:

ESP8266 development board to RS232 converter.

I can power the module using a standard micro USB cable and charger (just like you might already have for an Android phone or Raspberry Pi or some models of Arduinos).

After this, all I needed was a NULL Modem cable to connect that DB9 connector to the Serial I/O port of my Color Computer. In my case, I used a “Driverwire cable” which has a 4-pin DIN connector on one end and a DB9 on the other. I needed to use a NULL Modem adapter to get the signals talking.

ESP8266 ESP-12E devkit wired to DB9-to-TTL adapter and connected to a CoCo Drivewire (null modem) cable.

Cheap WiFi: ZIMODEM Software

The final step I needed to do was to install different firmware on the ESP8266. The firmware that comes on the module does allow you to type certain “AT” commands and connect to WiFi and remote systems, but I wanted something easier and more compatible. I found this ZIMODEM firmware:

https://github.com/bozimmerman/Zimodem

This makes the ESP8266 look like an old-style Hayes Smartmodem. Instead of using commands to dial a phone number, the commands will “dial” a remote telnet BBS. i.e., instead of:

ATDT 515-555-1212

…you can dial a telnet connection:

ATDT "coffeemud.net:23"

There are new commands added to display all nearby WiFi base stations, and connect to them. There’s even a command to retrieve a file from a web server! You can find full documentation on the ZIMODEM website.

Any terminal program can be used to make these types of connections. You can also configure it to receive incoming connections, and when someone telnets to your IP address, you will see a “RING” (just like the smartmodems did) and can have the system answer. Yep, it would be very easy to put an old-school BBS on the internet with this!

I was able to use this to connect an old Radio Shack CoCo to a remote BBS using the Greg-E-Term terminal program over the bitbanger port at 1200 baud (oooh, speedy).

Building and Installing ZIMODEM

I got these steps from the Amazon page for the ESP8266 part I purchased. I have edited them with additional notes and links.

Instruction & Steps of How to use:

  1. Download the latest version of the Arduino IDE. Today, there are versions of the IDE that run in a web browser (I have not tried these), as well as ones available for Mac, Windows and Linux. I used one for Windows 10, downloaded from the Microsoft Store.
  2. Install the IDE. (Well, duh…)
  3. Configure the Arduino IDE with support for the ESP8266:
    1. Go to File->Preferences and copy the URL below to get the ESP board manager extensions: arduino.esp8266.com/stable/package_esp8266com_index.json
    2.  Go to Tools > Board > Board Manager> Type “esp8266” and download the Community esp8266 and install.
    3. Set up your chip as:
      • Tools -> Board -> NodeMCU 1.0 (ESP-12E Module)
      • Tools -> Flash Size -> 4M (3M SPIFFS)
      • Tools -> CPU Frequency -> 80 Mhz
      • Tools -> Upload Speed -> 921600
      • Tools–>Port–> (whatever it is)
  4. Download and run the ESP8266 flasher program from Github:Win 32-bit: github.com/nodemcu/nodemcu-flasher/tree/master/Win32/Release
  5. To test that things are working, in Arduino IDE, look for the old fashioned Blink program (File->Examples->ESP8266->Blink). Load, compile and upload. If it worked, the module will have a blinking LED, indicating it is now running software you build using the Arduino IDE.
  6. Now all you have to do is download the ZIMODEM software, then open the main “zimodem.ino” file in the IDE (the other files will open in different tabs, automatically), and build and load it to the ESP8266.

UPDATE: I did not need step 4 when I recreated these steps on my Mac, so maybe they are not even needed on the PC side these days.

These steps worked for me, but I want to go back through them (as well as finding Mac instructions and Linux if someone can assist me with that) and add photos and more details.

FTP, IRC, TELNET and more! Oh my!

ZIMODEM was created for Commodore computers, and has some special features in it for translating normal ASCII to Commodore’s PETASCII. It also comes with steps on how to use it with a Commodore from BASIC (with some assembly language routines used for high-speed reading and writing to the modem – sound familiar?). They have source code for various internet utilities such as:

  • WGET (get a file from a website)
  • FTP
  • IRC (chat)
  • TELNET
  • TELNETD (for connecting to the Commodore remotely and using BASIC over the Internet)
  • WEATHER (a two player network game from the Commodore PET days)
  • …and others.

With DriveWire on the CoCo, some of this exists but only for OS-9. It is my hope that we can easily port these BASIC programs (and even replicate the assembly language routines) over to the CoCo and do the same thing.

More to come…

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