#rs232

[unixyouth]

Using ULIfAC and a TTL to RS232 converter together with EWEN Term on an Amstrad CPC 464 to connect to a SUN NETRA T1

[commodorez]

Comparing various 3rd party RS232 adapters for Commodore computers. From left to right:

Commodore S232 Adapter by Jameco for VIC-20/C64/C128

Link232 v1.2 by Brain Innovations for C64/C128

Dual Serial Cart Mk I by me for VIC-20

[techav]

RS232 and Reading from Compact Flash

I decided that instead of adding a MAX232 level shifter for RS232 serial directly to the board, I would be better off building a separate board. This would allow me to use the existing header with either the MAX232 or a TTL-USB adapter.

I got to use an interesting unique part on the MAX232 board — a quad capacitor network in DIP8 package. I couldn't find any similar parts still in production, and couldn't find any data sheets either. I got the part from a local electronics surplus shop, and it's perfect for use with a MAX232 because it's four 0.1μF capacitors in a convenient package.

I don't actually have a computer running right now with a proper RS232 serial port, so I used a USB-RS232 adapter to test with. I did have the Receive lines wired backwards at first, but other than that the breakout works. There is a weird quirk though that I have to connect it and turn on my 68000 computer before plugging it in to the other computer's USB port or else Receive doesn't work. Strange, but not really a show stopper.

So then I moved on to trying to read from the Compact Flash card. It's a no-name 64MB card that I've formatted FAT16. I've been looking at it by running:

$ sudo xxd /dev/disk4 | less

on my iMac to read the actual raw data from the card (especially the boot block and FAT). There is something immensely satisfying to see the exact same data come through my 68000 computer when reading the card as I got from the Mac with a proper card reader.

Now I need to figure out just how to interpret the FAT16 structures so I can add commands to the monitor for reading a file into memory.

[swarmik]

SAPI-1 (1983)

On the left side, you can see SAPI-1 – a professional computer that was made in the Czechoslovak Socialist Republic and was used mainly for industrial applications. Its architecture was modular and not very far from S100-bus computers. One of the cards contained CPU (Zilog Z80 in this case) while other cards contained RAM, ROM and communication interfaces. It was able to run CP/M which was loaded from 8-inch floppy drives.

This photo is from the last Bytefest show a few weeks ago. We were copying files over a null-modem cable from Amstrad CPC6128. File transfers between different CP/M computers were not an easy task back in the 80s. Each computer had different floppy drives or at least a different logical format of the disks. This was very similar to terminal incompatibilities where every full-screen program had to support tens of terminals in order to be compatible with most CP/M computers. If your computer was not on the list, you ended up with incorrect layout of the text on the screen.

Because of these incompatibilities, serial and modem connections were the best ways to transfer files back then and they are even today. Don’t expect something “plug and play”. Although I could set the transfer speed in software on Amstrad CPC6128, the owner of the SAPI-1 had to remove the communication card and change the serial link configuration using a soldering gun. Another issue was to find programs with compatible transfer protocols but that’s a different story. Finally, after less than an hour, we were able to copy all our precious files.

[michaelteeuw]

Activity board: Bake me some Pi!

Now that most of the firmware is all set an done, it's time to start working on the final part of the Activity Board: the Raspberry Pi display interface.

The activity board contains a simple 800x480 pixel HDMI display, so after simply connecting an Raspberry Pi I was quickly able to get my favorite Pi application running. The MagicMirror² framework!

Of course, this wasn't the type of information I want to display on the screen. But since the MagicMirror² is extremely robust and easy to set up, it is the perfect package to run the application on the activity board's display.

As a small test (and mainly as a placeholder) I quikly trew together a small configuration which looked cool. In the mean time I could start working on something more advanced.

Of course, I wanted to control the interface with all the different input options from the activity board, so I had to connect the Arduino and Raspberry Pi together. The simple wire displayed above was enough to let the two core components communicate over RS232 (Serial).

To read out the info the data the Arduino sends, I use the Node Serialport package. It took some head scratching to get it up and running, since I had to recompile it to work with Electron, but after that, it was pretty easy to set up the communication.

A MagicMirror's Node Helper sends the received serial data to a specially crafted MagicMirror² module.

The image above is captured over VNC. Isn't it awesome I can make a remote desktop connection to one of my kid's toys?!

The futuristic looking debug app allows me to test the communication. And is a perfect place holder to keep my son busy for a while ...

The module leverages the power of Vue.js to quickly develop the interface. It took some fiddling to get a Vue.js working as a MagicMirror module, but is does show the flexibility of the MagicMirror² core. If you're interested in how it's all tied together, check out the module's repository.

And with this interface, the technology of the activity board is fully tested. The only thing left is the development of an addictive interface which keeps my son busy while I'm tinkering behind my desk. Perfect parenting!

Read all posts in this series:

Part 1: Enzo’s Control Room Part 2: Building the Box Part 3: Fire up the Lasers! Part 4: Spray Away! Part 5: Push the button! Part 6: Assembling the panel Part 7: The dial on the board goes round and round Part 8: Take control! Part 9: It’s all about the code! Part 10: Bake me some Pi! Part 11: The Final Touch

[commodorez]

@tumblokami​ ordered up some PCBs and gathered the parts to make a few of Geoff Graham’s ASCII Video Terminal board kits. 

I enjoy small projects like this that serve a unique compact function, and I certainly can find a use for another serial terminal. It provides VGA or composite video output, PS/2 input, and TTL serial output (which I adapted to RS232 voltage levels).

[commodorez]

Solderless Breadboard Compilation

A useful tool for all kinds of prototyping!  Seen here are examples of (in no particular order):

Executing NOPs on an MOS6502, and building a data entry circuit

Crudely adjusting brightness/contrast of a composite video signal

Improving upon the data entry/modification circuit for my 6502 homebrew computer, and testing with an MCM6810

Approximating the function of a Dekatron tube in count-up mode

Dividing a 32 MHz oscillation down to 8MHz

Controlling a device over RS232 via rotary encoder

Reading the contents of an EPROM, one byte at a time

Combining sync and pixel signals to create a proper composite video source

Making phone calls with a rotary dial over the cellular network

[swarmik]

Headless SGI workstation?

No problem, if you have a null-modem cable and terminal emulator software. SGI O2 (and other MIPS-based SGI workstations) uses the first serial port as the main output for all system messages and OS console if no keyboard is attached (or if firmware is set to prioritize the serial connection). You can access firmware settings, install IRIX to an empty hard drive or boot the system. This is a full replacement for keyboard and mouse unless you need graphics.

IRIX allows you to configure both serial ports to handle terminal connection (other options are MIDI and standard serial interface) so you can have three users working with one computer locally.