I like to take things apart. Sometimes they work when I'm done. I've been a member of NYC Resistor since 2010 and you can see more of my projects at

Aug 212012

Ghosts in the ROM

While digging through dumps generated from the Apple Mac SE ROM images we noticed that there was a large amount of non-code, non-audio data. Adam Mayer tested different stride widths and found that at 67 bytes (536 pixels across) there appeared to be some sort of image data that clearly was a picture of people. The rest of the image was skewed and distorted, so we knew that it wasn’t stored as an uncompressed bitmap.

After some investigation, we were able to decode the scrambled mess above and turn it into the full image with a hidden message from “Thu, Nov 20, 1986“:

Mac SE engineers (0x1D93C)

Read on for the reverse engineering details of how we recovered this and the other three photographs stored in the ROM, and some information about the Motorola 68000 era Macintosh.
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 Posted by at 10:13 pm
Aug 052012

IBM 83 card sorter, wiring harness

This is neither a tree root nor an eldritch horror — it is a thirty year old wiring harness from a punch card sorter. If you enjoyed our IBM 129 card data recorder restoration or are a fan of vacuum tube era design and mechanical engineering, you might also be interested to see what we found inside an IBM 83 card sorter.
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 Posted by at 3:30 pm
Jul 292012

PROM dumper

So you want to dump a ROM, but don’t have a breadboard? You can use a Teensy, some female-female jumpers and if you have one, a ZIF socket. I cut the power and ground wires and soldered three additional leads to each one to provide hard-wired values for for Vpp and !PGM signals at +5V, and the !CS and !OE signals at ground potential. To make wiring easier, my code in prom.c maps the address lines sequentially down the left side of the Teensy, and the data lines sequentially down the right side. Using every pin on the teensy provides 14 bits of address line and 8 bits of data, allowing up to 16 KB PROMs to be dumped.
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 Posted by at 10:27 pm
Jul 192012

Standing desk with foot pedals

I’ve recently switched to a standing desk from Geek Desk and wanted to be able to free my hands for more important things, like drinking coffee. The foot pedals are a cast off Behringer FCB1010 MIDI foot controller, which outputs events as MIDI messages. To make it work with any computer without requiring additional software, I wrote a combination MIDI to USB HID mouse and keyboard converter that runs on a Teensy 2.0.

The Teensy translates the pedal events into various mouse or keyboard events (Escape to return to command mode in vi, Shift-Insert to paste the X11 cut buffer, mouse wheel events for the pedals, etc). Full source is available to build your own and configure your own mappings. Read on for some details on the hardware interface.
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 Posted by at 8:50 pm


 Uncategorized  1 Response »
Apr 052012

alternate reality. #hackfriday

Last November, johngineer proposed #hackfriday, a day for hackerspaces to work on projects. Tomorrow is a holiday from work for many of us, so a bunch of will be hacking away at NYC Resistor. What projects will you work on this long weekend?

 Posted by at 10:18 pm
Mar 112012

4x5 to 35mm adapter

I recently acquired an early 1900′s Gundlach 4×5 view camera with a few lenses and designed an adapter to mount a modern DSLR body where the film plane would go. There is no lens connected to the SLR — the 4×5 lens images directly onto the CMOS sensor. The bracket design is thing:18989 and can likely be adapted for other field or monorail cameras. There are some limitations with the design, but it works acceptably well in practice.

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 Posted by at 11:09 pm