hudson

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 trmm.net.

Apr 092014
 

NYCR floor painting: BeforeNYCR floor painting: before
Did you ever notice how beat-up the floors were at NYC Resistor? Four years of rolling chairs had done horrible things to the paint, so we did something about it last night.

NYCR floor paintingNYCR floor painting
Everybody pitched in with a massive effort. While the painting only took from 22.8 to 73.3 .beats, the spring cleaning, organization and preparation took all weekend.

NYCR floor paintingNYCR floor painting
Zach was the last Resistor painting and escaped by taking the elevator. We turned off the lights and let the first coat dry overnight. The second coat will be dry in time for Craft Night. So come hack with us on a freshly painted floors!

 Posted by at 10:46 pm
Feb 252014
 

The Spikenzie Labs Solder:Time Desk Clock is a fun through-hole kit to solder together. It includes a snap-together lasercut acrylic case with a really nice red tinted screen that increases the contrast on the 20×7 red LED matrix. Plus it is totally hackable with quite a few unused pins available for expansion (like Holly’s sunrise alarm clock).

The kit is available from Adafruit and I’ve written more information on information on programming custom firmware for the Arduino-compatible ATmega328P that is the brains of the clock.

Feb 092014
 

Voronoi shadows

Given a set of points, the Voronoi tessellation creates a set of convex polygons that each contain one point. They can also be used to randomly generate unique art pieces that cast shifting, lace-like shadows. This one was really quite beautiful until the candle burned through…

Read on for some scripts to make your own and tips for laser cutting them.
Continue reading »

Feb 022014
 

Firefox on a Mac SEMac SE video driver

It is a truth, universally acknowledged, that an engineer in possession of an antique computer must be in want of hacking it. Last year I reverse engineered the Easter Egg photographs from a Mac SE that I found on the side of the road and that machine has been sitting idle since then, so I took inspiration from NYCR founder Dave Clausen’s six year old 24th anniversary Mac project and turned my old SE into a “30th anniversary Macintosh” with a new ARM motherboard running Linux. Unlike Dave, I was able to interface with the original 9″ CRT thanks to the programmable hardware in the Beaglebone Black.

Mac SE video pulses
The CRT was still in good shape and the m68k motherboard would startup (although we have no media or OS for it) so it was fairly easy to reverse engineer the pinout and waveforms for the combination power-supply and video connector. The all-in-one Macs shared a common power-supply for the monitor, analog board, motherboard and drives, so the same cable carries video, hsync, vsync, +5, -5, +12 and -12 Volts.

Mac SE video driver
With these timing measurements I was able to write a software video card that runs inside the BeagleBone Black’s PRU to display a user-space framebuffer, and then used Xvfb to render X11 into a shared memory buffer that could be exported to the PRU’s memory. Working with a bare CRT like this can be scary — the monitor is not even remotely multisync and vsync a few percent off from its desired 60.1 Hz refresh rate generates very bad buzzing sounds.

[flickr video=12200336913 show_info=no w=640 h=380]
You can enjoy the dithered 1-bit cat videos above and relive the era with monochrome visuals for xeyes and other classic applications. If you want to build your own and see the specifics of the design, there are more details on my website, trmm.net/Mac-SE_video.

Mac SE with a BeagleBone Black motherboard
UPDATE 2014-02-09: Original ADB Keyboard and mouse support is now working. adb2usb source code for a Teensy 2.0.

Dec 082013
 

Adafruit FLORA and Neopixel ring

Next weekend at NYC Resistor we are teaching a class on the Adafruit FLORA and Neopixel. These round Arduino compatible controller boards are a great base for wearable projects like watches, jackets and neck ties, as well as holiday decorations. Bring your laptop and we’ll teach you to make the LED ring blink with patterns of your own design. No prior programming required. The class fee includes a FLORA board, batteries, cabling, 4 RGB LED pixels and a 16 RGB LED ring.

Nov 182013
 

AVR RFID with extra capacitor

Last year we wrote about building HID Proxcard RFID tags with attiny85 microcontrollers (based on Micah’s avrfid.s code). The C version only supported classic 26-bit cards, but I recently needed to support the “secure” HID Corporate 1000 35-bit format.

Based on Daniel Smith’s writeup on the format and some digging around, I figured out that the MFG_CODE for this format is 10-bits long with the value 0x005. He also pointed out that the 26-bit firmware had the wrong code — it is not the 20-bit code 0x01002, but is instead the 19-bit code 0x0801 and the bottom bit is part of the parity computation for the card id. If you’re using a HID branded Proxcard reader, the value that it outputs is the entire data portion, including all of the parity bits, but does not include the MFC_CODE part. If anyone knows of a table of these codes, please let me know!

I’ve updated my firmware with these changes and it works great. Emulating a 35-bit card takes 846 bytes of flash (nine more than the 26-bit cards since the state machine stores one bit per byte), so it might be possible to port this to the attiny10. I’ve also found that the tags work much better with a small capacitor across the two clock pins, as shown in the above photo.

Octoscroller

 Uncategorized  6 Responses »
Sep 122013
 

Octoscroller temporary installation

Hexascroller has been a central fixture at NYCR for the past few years, with a few ups and downs. It’s replacement, Octoscroller, improves on our classic message alert polygon by having two more sides and two more colors of LEDs.

The userspace application renders images into a shared memory frame buffer, or in this case receives UDP packets containing video images from the Disorient Pyramid transmitter. The PWM algorithm can do between eight and sixteen levels of brightness for each color, producing approximately 12-bit color.

See it in person at MakerFaire in NYC this year and read on for details of how to wire up a driver for the panels, as well as a walkthrough of some of the PRU code.
Continue reading »

 Posted by at 9:41 pm
Sep 052013
 

Party at the Disorient Pyramid

This year the Disorient Camp at Burning Man built a 7m tall pyramid with over half a kilometer of LED strips. Several artists developed patterns for the panels, including Disorient founder Leo Villareal and Jacob Joaquin from Fresno Idea Works. Every night there was a party in front of the pyramid, with bicycles blocking the entire Esplanade.

The pyramid was visible from just about everywhere on the playa and served as a great beacon for finding the camp after a long night out. Read more for the technical details of how it was constructed and links to all the source code.
Continue reading »

 Posted by at 11:07 pm

Oscilloscope class

 Uncategorized  1 Response »
Aug 042013
 

Diagnosing EL wire with a DSO Nano v3

One of the most powerful tools in debugging circuits is the oscilloscope — it allows you to visualize your analog and digital signals at millisecond or microsecond time scales. This 18 August class at NYC Resistor will teach you basic operation of a handheld oscilloscope: topics include how to setup different time and voltage scales, how to configure the trigger modes to capture fleeting signals and how to use the cursors to measure various qualities of the signals. We’ll also show how to use the ‘scope to trace a signal through a circuit to identify some common problems.

Multimeter amperage measurement

The other most valuable tool in your electrical test equipment toolbox is a multimeter for measuring the instantaneous values of three important electrical measurements: voltage, amperage and resistance. This class covers all three of these as well as the very important “beep mode” to check for electrical connectivity.

Get your tickets here! The class fee includes both a compact multimeter and a DSO Nano v3, an Open Hardware design that is a great getting started oscilloscope. With these in your toolbox you’ll be able to diagnose all manners of circuit issues.

 Posted by at 3:12 pm