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  • Author Author: mcollinge
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Episode 386: Xybernaut Wearable PC

 

The Xybernaut Mobile Assistant was one of the earliest attempts at wearable computers--way back in the 1990s! It was an interesting feat of engineering for the time, but technological limitations, a high price tag, and contemporary interface design conventions stood in the way of mainstream success. Matt ran across one of the later models--the MAIV--that was dead-on-arrival, but wanted to add it to his retro computer collection. So with very little documentation available (The Xybernaut corporation went bust in the early 2000s after several commercial flops and some financial chicanery), he tore it down to see what powered it and set about to rebuild it with modern components. Was the Xybernaut a viable platform in hindsight? Is Minesweeper playable on a 2" head-mounted display? Why didn't arm-mounted keyboards catch on? These and more questions will be answered in this week's element14 Presents!

 

Supplemental Content:

 

 

Bill of Material:

 

PartManufacturerQuantityBuy Kit

Raspberry Pi 3 Model B+, Starter Kit

element141Buy Now

D Sub Connector, DB15, 15 Contacts, Plug, Solder, DA, AMPLIMITE HDP-20 Series, Steel Body

AMP - TE CONNECTIVITY1Buy Now
D Sub Connector, DB15, 15 Contacts, Receptacle, Solder, DA, D Series, Metal BodyAMPHENOL ICC (FCI)1Buy Now
D Sub Backshell, Diecast, Rapid Assembly, Shielded, MHDM Series, DA, 180°, Zinc BodyMH CONNECTORS1Buy Now
USB Cable, USB Type A Plug, Micro USB Type B Plug, 152.4 m, 6 ", USB 2.0, BlackSTELLAR LABS COMPUTER PLUS1Buy Now
1.8 Color TFT LCD display with MicroSD Card Breakout - ST7735RADAFRUIT 1Buy Now
Development Board, AdaFruit Feather, ATmega32u4, Prototyping AreaADAFRUIT1Buy Now
Tactile Switch, B3F Series, Top Actuated, Through Hole, Plunger for Cap, 260 gf, 50mA at 24VDCOMRON ELECTRONIC COMPONENTS2Buy Now
Toggle Switch, On-On, SPDT, Non Illuminated, 1MS1T1B1M1 Series, 5 A, Panel MountMULTICOMP1Buy Now

 

Additional Parts:

 

Product Name

ADAFRUIT Thumb joystick (x1)

Xybernaut MAIV Computer platform (x1)

Attachments:
STL Files.zip
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  • Super cool use for QEMU. I had never thought about running it on a Pi for (what is now) vintage PC emulation.

     

    Regarding your display, two thoughts come to mind. Both related to the resistance of the cable, as you mentioned.

     

    1. Measure the voltage drop of the cable. Check the supply voltage going in and coming out, see how much you're dropping. That'll give you some idea. More than 250 mV and that's pretty significant. It's possible a larger decoupling capacitor on the display side might help. Changes in load current would result in funky voltage drops with all of that stray capacitance and inductance. However, more likely is #2.

     

    2. How fast is the SPI bus running? Similar to the test above, using a scope to measure the SCK on both sides of the cable. Make sure you clip your ground clip to the same side as well. (And for fun, keep the clip on opposite sides for a different measurement.) If you don't have a clean square wave on the display side, you know the impedance of the cable is killing it. A useful troubleshooting step would be to change the SPI speed. Slowing it down should help.

  • in reply to baldengineer

    Thanks, James! I appreciate the insight--it might be a good opportunity to take my new scope for a spin! I'll probably incorporate that into "Project Mouthwash" once I get that underway

     

    QEMU seems to be a pretty decent solution for virtualization on RPi, but--of course--it's not perfect. Nice thing is that you can easily add it to rc.local so it's pretty seamless on boot!

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  • in reply to baldengineer

    Thanks, James! I appreciate the insight--it might be a good opportunity to take my new scope for a spin! I'll probably incorporate that into "Project Mouthwash" once I get that underway

     

    QEMU seems to be a pretty decent solution for virtualization on RPi, but--of course--it's not perfect. Nice thing is that you can easily add it to rc.local so it's pretty seamless on boot!

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