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


 Uncategorized  2 Responses »
Nov 182012

A quarter past

I found Matt Joyce’s HDSP211x alphanumeric displays in the LED bin at NYCR and loved the StarTAC style. He had previously written about driving them, but using an Arduino and a shift register on a breadboard was a bit large for my goal of making it into a wristwatch.

Teensy backpack for the HDS2111 LED display

I noticed that the PDIP spacing was the same as the Teensy 2.0 and, much like my ROM dumper, hoped that it could fit on the back of the display with almost no additional wires. Read on for the “schematics” and source code details.
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 Posted by at 3:50 pm

Robot Army

 Uncategorized  7 Responses »
Nov 132012

Three PUMA arms

A friend recently acquired a set of PUMA 260 / RP Automation robot arms and asked for some assistance in getting them running again.

PUMA wiring harness

Unfortunately they had been removed from their previous occupation with a set of wire-cutters. Some wires were labeled, most were not. But after a few weekends with a multimeter and some oscilloscope work, we have it running again. Read on for how to bring these arms back to life.
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 Posted by at 9:30 pm
Oct 072012

USB mill controller and e-stop

Do you want to be able to control software with interesting things?

USB Iambic Morse Keyboard

Do you want to type text in a weird way?

WASD keyboard

Do you often need to type just the W-A-S-D and space keys?

"Hack it"
Standing desk with foot pedals

Or do you have have ideas for repurposing devices to connect them to your computer? Then sign up for the USB Human Input Device class at NYC Resistor next weekend, 14 October 2012!

The class covers writing firmware for the AVR to implement various USB HID classes, such as keyboards, mice and joysticks, using both raw USB calls and Arduino libraries. Included in the class is a Teensy 2.0, a breadboard and switches for building a simple human input device that you can take home to prototype your next gadget project. Anything with buttons, pedals, sliders or knobs can be used to make an input device once you know how!

 Posted by at 10:21 am

USB Analog Gauge

 Uncategorized  4 Responses »
Sep 172012

Badass gauges

Perhaps at your hackerspace you have a pile of “badass gauges” and want to do something with them. How about a USB interface, a laser cut enclosure and an RGB status indicator LED?

USB Gauge

Read on for the vague construction details and some software to drive random DC current and voltage gauges that you might find.
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 Posted by at 8:59 pm
Sep 032012

Vector clock

Vector displays are now mostly historical oddities — old arcade games like Asteroids or Tempest, or ancient FAA radar displays — which gives them a certain charm. Unlike modern raster displays, the electron beam in the CRT is not swept left to right and top to bottom for each row in the image. Instead the beam is steered to a point and traces the lines of the displayed image.

Most dual channel oscilloscopes have an XY mode in which the timebase is replaced by the second channel, so instead of a constant sweep frequency the two inputs to be plotted relative to each other. Generating low frequency analog voltages out of a small microcontroller with PWM through a low pass filter is quite common for adjusting the brightness of an LEd, but drawing complex shapes requires a faster way to change the voltage. One very easy way to do this is with an R-2R ladder DAC.

Read on for more details about how to build your own vector display hardware and some ways to draw shapes on your oscilloscope’s screen.
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 Posted by at 10:10 pm
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