Yesterday’s post mentioned some hypothetical marsupial-themed hardware: WiFi Wallaby, Video Platypus, and others. While these were meant as a joke, they got me thinking about what exactly a “Video Platypus” and friends might do, and I’m outlining some possibilities below. These are all tied loosely into vintage Macintosh hardware, although other ideas of interest to the general Arduino/RPi audience would be nice too.

 
Video Platypus

This might be a way of providing video out for compact Macs like the Plus and SE. I’ve discussed a few potential methods for doing this before. One approach is to directly tap the CRT video and synchronization signals and resample/convert them to a standard format. Another possibility is sniffing the address and data bus to watch for CPU writes to the framebuffer region of main memory, then use that to construct a new video signal.

Video Platypus could also be a converter or upscaler for the Mac II series and later machines. VGA adapters for these machines are inexpensive and easy to find, but VGA itself is a slowly dying standard. It would be nice if I could get a direct HDMI or DVI-D output from my 680X0 or PowerMac. Probably this wouldn’t need to be Mac-specific – it would just be a VGA to HDMI converter with a different physical connector to support the Mac. Something like this must surely exist already?

 
Disk Kangaroo

An external fileserver would be nice for old Macintosh computers: a device you plug into the computer and that appears as a large local or remote disk. Floppy Emu already serves this purpose when it’s configured in HD20 hard disk mode, but only a small number of Macintosh models support HD20 and have the necessary external floppy connector.

Disk Kangaroo could be something like a Floppy Emu for LocalTalk. Just plug it into the Mac’s LocalTalk port (the printer port), and it would appear as a fileserver. You wouldn’t be able to boot from it the way you can from Floppy Emu, but it would work on virtually every Mac model and system software version. The I/O speed would be about the same as Floppy Emu, I think.

The same idea could be applied to a SCSI disk instead, so the device would appear as a local disk and the computer could boot from it. This would be similar to SCSI2SD, except instead of formatting the whole SD card as a Macintosh disk, the SD card would contain a library of disk images to choose from, just like Floppy Emu. This would make it easier to set up and use for file transfers to and from an internet-connected PC.

Both the SCSI and LocalTalk disks could also use remote storage instead of an SD card. The files could be served from a PC on the same LAN, which would might require some special software on the PC, or the device could potentially do Appletalk-to-Samba translation. Or files could be served directly from a cloud storage account like DropBox.

 
WiFi Wallaby

Everybody loves the ESP8266 for connecting oddball things to WiFi. What might this do for a vintage computer? Most old Macs are capable of Ethernet networking, although many require an add-in networking card that’s now rare. I’m not sure if it’s easy or even possible to go from that to a wireless network connection.

What might you use this wireless connection for – general web surfing, email, and FTP? Or for connecting to other vintage Apple computers and printers wirelessly with Appletalk?

Maybe this could be like a WiFi version of Farallon PhoneNet. Connect a WiFi Wallaby to each of your computers and printers and they’ll auto-connect and form an Appletalk network. Same idea as the phone cables in PhoneNet, but wireless.

 
Printer Koala

A clever microcontroller board with the necessary physical connector could emulate an Imagewriter II or other 80’s – 90’s Apple printer. What would be the point of that? Maybe it could act as a print server or translator, enabling the old Macs to use modern printers. The need for printer drivers could make that difficult, though. Or maybe “printing” could perform another function like converting the document to PDF and storing it on an SD card or on a cloud-based server. Or it might implement a print-to-Facebook or print-to-Twitter feature.

Working in the opposite direction could be interesting too: a device that connects to an Imagewriter II or Stylewriter or LaserWriter. The device could put these classic printers on a network so that modern computers could print to them from Windows, OSX, or Linux. There would be a question of printer drivers again, but for relatively simple printers like the Imagewriter that might be doable.

Read 6 comments and join the conversation 

Oops. I belatedly discovered there’s already a Nintendo emulator called Retro USB, which means I need a new name for my USB/ADB input converter. After an exhaustive 5-minute naming process, I’ve decided to continue Floppy Emu’s Australian animal theme and call it USB Wombat. The Australians sure do have plenty of oddball animals to choose from. Coming soon: WiFi Wallaby and Video Platypus?

I’ll update the web site and documentation with the new name soon, but the hardware will keep the Retro USB logo until I exhaust the current supply of boards. The prototype enclosure will need to be updated too. It’s a time-consuming hassle when I’d rather focus on other work, but if a name change is required, it’s surely better to do it sooner rather than later.

Read 9 comments and join the conversation 

Some good news for Retro USB this week: new hardware, international keyboard improvements, and an enclosure prototype! Everything is maturing nicely, thanks to feedback and assistance from some helpful early adopters. More hardware is available, if you haven’t yet gotten yours. Forward ho!

For anybody who’s newly tuning in, Retro USB is an input converter for USB and ADB keyboards and mice. It works in two directions, connecting modern USB peripherals to a classic ADB-based Macintosh or Apple IIgs computer, or ADB peripherals to a USB-based computer running Windows, OSX, or Linux.

 
Board Version 1.2

After a slightly bumpy start, I’ve finally perfected the PCB design with version 1.2. This is the first version whose assembly won’t require me to apply manual fix-ups for my design mistakes, so the assembly process can be simpler and faster. It doesn’t make any difference to the final product, but hand-soldering patch wires and extra resistors is tiresome work. I’m very glad to be rid of that job.

The most significant change in board version 1.2 is the addition of a 1000 uF bulk capacitor for the USB power supply. This enables Retro USB to handle brief spikes in power demand from attached devices, such as the spikes from an Apple A1243 keyboard during its initialization. With this capacitor, there are no problems with “spiky” USB devices like the A1243. The built-in hub on the A1243 works too, and is a convenient spot to attach the mouse.

A bulk capacitor can be retrofit to board versions 1.0 and 1.1, if you’re comfortable with some basic soldering. You’ll need a capacitor of 680 uF or more, with a voltage rating of 6.0 volts or more, like this example. Solder the capacitor’s negative terminal to the board’s GND and the capacitor’s positive terminal to the board’s VUSB. See the photos for the board locations to use.

 
International Keyboards

Firmware version 0.1.15 resolves a few remaining issues for non-US keyboards, and layouts from French to Danish to Estonian and everything in between should now be working, in both USB-to-ADB and ADB-to-USB directions. Please see the International Keyboards section on the main Retro USB page for important details.

For correct key mapping with non-US keyboards:

• Choose the appropriate keyboard type in your operating system’s keyboard control panel or language preferences
• Set Retro USB to ISO mode (automatic for many keyboard models)

For many countries outside the USA, the USB keyboards designed for Windows PCs have a different layout than Apple keyboards. These PC-type USB keyboards may be used, but key mappings for some symbols will be incorrect where differences exist between the Apple and PC-type layouts. Best results will be obtained with Apple-brand non-US keyboards, or any brand US-layout keyboards.

 
Other Firmware Improvements

See the change notes included with the latest firmware for a complete list of what’s new. Here are the highlights:

• Right mouse button now works on NeXT computers
• Resolved an issue that prevented ADB keyboard capslock from functioning with macOS Sierra
• Fixed the output from help commands to appear correctly when using a non-QWERTY keyboard
• Fixed missed ADB keyboard events if the mouse is moved while typing
• Fixed device initialization when using multiple cascaded USB hubs
• Added new help command Control-Shift-Capslock-G to show the current keymap type

 
Enclosure Prototype

I’m working on a simple enclosure to protect the Retro USB board and add a touch of style. It’s gloss black 1.5 mm acrylic with an engraved logo, and cut to the same shape as the PCB. Add a few spacers and screws, and it makes a nice little package that’s easy to assemble. Initially I’d planned to make a fully-enclosed 6-sided box, but I would have needed to lose the rounded corners, and my experience with the Floppy Emu enclosure has taught me that 6-sided laser-cut enclosures can be awkward to put together. I quite like the appearance and simplicity of this enclosure, and it will probably show up in the store soon.

 
What’s Next?

Although the start was a little chaotic, Retro USB’s software and hardware now are both looking good, and the device can truly deliver on its plug-and-go promise for ADB and USB conversion. On the software side I’ll be looking at multi-button mouse support soon, so stay tuned for that. For the hardware, most of the effort will go into improving the assembly and testing process, and transitioning away from hand assembly. After that, we will see what else takes shape!

Read 1 comment and join the conversation 

Looking for a creative project for kids to build? The Electric Scribble Machine is an entertaining device that’s easy to build from common parts – great for a scout troop project, school science fair, or just a lazy afternoon at home. For the past several years, as part of our local elementary school’s annual Discovery Day, I’ve led groups of kids ages 7-11 through the construction of a scribble machine. Tomorrow will be my last turn at Discovery Day, so I’m documenting the scribble machine design here for reference.

The basic concept is simple, and is borrowed from an Exploratorium design:

• An off-center weight on an electric motor will cause it to wobble and vibrate
• Mount the wobbly motor to a body made of plastic, cardboard, recycled bottles, or whatever’s available
• Attach colored felt-tip markers to the body to create legs

When the machine is placed on a large sheet of paper, it will wobble and jump around erratically, drawing interesting patterns as it moves.

 
Step 1 – Motor

I use cheap DC hobby motors rated for 1.5V to 6.0V. They work fine with just a single AA battery, but are better with 2xAA batteries.

 
Step 2 – Off-Center Weight

Anything that can be mounted onto the motor’s shaft will work. The more unevenly the weight is distributed, the better. I’ve found that glue sticks for hot glue guns work nicely, and are easy to mount thanks to their texture.

I use generic 4 x 0.44 inch glue sticks, and cut them in half with kitchen scissors to make 2 inch sticks. I hammer in a finishing nail near one end of the stick, then pull out the nail, leaving a small hole behind. The hole makes it easy to press-fit the glue stick onto the motor shaft without any additional tools: just push the shaft into the hole. The rubbery texture of the glue stick holds the shaft tightly, so it won’t easily pull loose.

 
Step 3 – Battery Holder (optional)

A 2xAA battery holder with an integrated on-off switch helps to create a reliable finished project. In the first years of building scribble machines, I held the motor wires directly to the battery terminals with rubber bands. It worked, but was a constant source of frustration when the wires came loose.

I’ve found that the wires on cheap battery holders are often poor quality, and break easily. Last year, about half of the battery holder / motor units suffered some kind of wire breakage during the day, leading to a lot of unhappy kids and emergency solder repairs. This year, I’ve added a drop of hot glue to the outside of each battery holder at the point where the wires exit. I’m hoping this will serve as a strain relief, and help reduce the number of broken wires.

 
Step 4 – Soldering (optional)

For the most reliable results, the battery holder wires should be soldered to the motor terminals. This is as easy as soldering gets, and it takes only a few seconds. A $15 Radio Shack soldering iron will do the job nicely.

As an alternative to soldering, the battery holder wires could be twisted around the motor terminals with pliers. There’s normally a small hole in the center of each motor terminal, which makes the job fairly easy.

 
Step 5 – The Body

Here’s an opportunity to get really creative – the body can be made from virtually anything! Try empty water bottles, plastic baskets, DVDs, cardboard, foam board, or whatever else might be handy. In past years I used empty plastic water bottles, sometimes with a few rocks inside to act as ballast. The plastic bottles work fairly well, although they do sometimes get partly crushed by kids who are overzealous in their construction efforts.

This year I’m trying something new: flat cardboard bodies, with holes drilled for the motor and felt-tip markers. It’s definitely possible to create these from old cardboard boxes, but cutting and drilling is time-consuming and tedious when making more than one or two. I took the easy path, and got squares of laser-cut double-thickness cardboard made by a local service. They were only 84 cents each, and the precise cut-outs for the motor and markers make it easy to snap the components into place. I added eight holes for markers, so the kids can experiment with different placements.

You’re welcome to use my laser-cut design. The Ponoko service will make them for you, if you add the design to your “personal factory” and select a material. Mine were cut from double layer corrugated cardboard, 6.7 mm thickness, 181 x 181 mm size (Ponoko’s standard P1 size).

 
Step 6 – The Legs

The legs of the Electric Scribbling Machine are generic colored felt-tip markers. Many parents already have dozens of these stuffed into every odd drawer and closet. Washable markers are nice for recovering from accidents, but not required. I used this cheap 30-pack of fine tip markers.

Three legs or four? I’ve tried both, but usually go with four. The design of the scribble machine requires some fine-tuning of stability, and four legs create a more stable base than three. Too much stability isn’t necessarily a good thing, however, since a certain degree of wobbling is required to make a good scribble design. But a high degree of wobbling will quickly lead to wild gyrations, and then the machine will topple over in a sad pile. It takes a few minutes of experimentation with leg lengths and ballast weights to find a happy medium.

 
Step 7 – Assembly and Use

I normally prepare the battery packs, motors, and glue sticks ahead of time. On the day of the event, the kids combine these with the batteries, body, and legs to assemble a finished machine. It sounds simple, but the assembly process always seems to require a surprisingly large amount of time, usually 30 minutes or more.

Duct tape, masking tape, rubber bands, or hot glue can be used to mount the motor and battery pack onto the body. These are the heaviest components, so it’s best to place them near the center of the body. I’ve found that most 7 to 11-year-olds don’t have the physical dexterity to work with rubber bands, so duct tape is my preferred adhesive method. After mounting the motor and battery, the legs are attached the same way. The caps on the markers add about 1.5 inches to their length, which needs to be considered while mounting them, otherwise the finished machine will sit too low to the ground when the caps are removed.

After watching the machine scribble random designs for a while, it’s time for some directed experiments.

• What happens if one leg is a different length than the others?
• What’s the effect of moving the legs closer to or further from the body’s center of mass?
• Can you configure the machine to wobble forward in a straight line instead of gyrating randomly? Try racing them.
• Reconfigure the motor to lie on its side, spinning the weight in the vertical plane. How does the machine’s motion change?
• Decorate the bodies with stickers and give them cool names.

 
Shopping List

Supplies for 30 kids:

30 electric motors $45.00
15 hot glue gun sticks $8.69
30 battery holders $24.36
60 AA batteries $11.87
30 laser-cut cardboard bodies $25.20
100 colored markers $17.44

The total cost is about $132, or $4.42 each.

If you build an Electric Scribble Machine, send me a note and tell me how it went!

Be the first to comment! 

I received a large number of new Retro USB PCBs today, which include a few small component changes from the 1.0 design. Bad news: I blundered by reversing the gate and drain connections on the MOSFETs used for level conversion. DOH!! Always read the datasheet carefully, boys and girls. On a 3-pin device, I must have assumed the gate would be the pin on the side by itself, with drain and source paired up on the other side, just like the canonical drawing of a transistor. Unfortunately that’s not true here. Hopefully I can find another brand of SOT-23 N-channel MOSFET whose pins are organized the way I thought they should be, or else this whole pile of PCBs is going into the trash. For a moment I thought maybe I could rotate the MOSFET 120 degrees, or even mount it upside down, but I don’t think any soldering tricks can save me.

Read 5 comments and join the conversation