The above line was actually directly written from an old-fashioned punch card! How? Via my DIY punch-card-to-keyboard interface
It all started with a conversation with a colleague about the good-old-times of computers, when de-bugging was still removing live animals. A few days later he dropped by my office and handed me a bunch of cards of ‘Druckwerke Reichenbach’.
Initially I tried reading the cards with a mechanical contact, but this quickly turned out to be highly unreliable. Around the same time I had disassembled some old HP office print stations, which resulted in a large number of useful parts. Some stepper motors, some solenoids, and heaps of slotted optical interrupter switches. Following a tip of another colleague, I started disassembling the switches into IR-LEDs and corresponding photo-transistors.
Using these components I build a new prototype, this time using contactless optical sensors. I drilled opposing holes into two plastic cards. On one side I glued the LEDs and on the other side the photo-transistors. The LEDs are powered by 3.3V chaining 3 LEDs serial and 4 groups parallel. The transistors use a common ground and are connected to the Teensy 3.1 inputs. The inputs have activated pull-up resistors, pulling them to 3.3V as well. With a free passage between the LED and the transistor, the light activates the transistor, which in turn pulls the input to ground. With the card in between, the transistor receives no light and let’s the input be pulled up to 3.3V. Thus the input pins follow an inverted logic.
The two plastic plates are separated by two plastic guides to each side of the card. They provide guidance to the card when inserted, which is important for the correct hole alignment. As the optical card reader turned out to work rather reliable, I implemented a simple interpreter on the Teensy 3.1 which reads the card according to the IBM model 029 keypunch from the 60’s / 70’s. The micro-controller is recognised as a USB HID keyboard and sends the decoded characters as key presses. Each card is finalised with an ‘enter’ key press. The only adjustments I made are to only use every second column of the card in order to make sure all contacts close after each character. Also I added a space character encoding (Y&X row). You can download the binary and source code for the Teensy 3.1 based decoder from github.
Now all that’s left is to do is to use this device and send a ‘HELLO WORLD!’ tweet directly from punch card
Today I received the ESP8266EX Serial -> WiFi modules! After not being convinced by the rather expensive Adafruit TI CC3000 (35USD!) module I am now very curious about these tiny and cheap (<4USD) modules.
As their default header (2X4 male) is not exactly breadboard friendly, I sat down today and soldered a simple breadboard adapter. All you need is a tiny piece of stripboard 4×4, two male headers 1×4, two female headers 1×4 or one female header 2×4, and a bit of hot glue.
Cut the stripboard to the correct size (4×4) and sandpaper any rough edges. Use a file to separate the copper strips across the middle.
Place the female header on a breadboard using the male headers to give it some stability and solder it to the stripboard. Watch out for the correct orientation!
Re-align the plastic spacer of the male headers all the way to the top.
Place the stripboard with the male headers inserted from the non-copper side on some support (I used my vice for this).
Solder the male headers to the stripboard.
Now replace the plastic spacer of the male headers to the bottom side and push it as far up as possible (it probably will not go all the way because of the solder)
Add some hot glue around the tips of the male headers to provide additional support and strength.
The first tests using the Bus Pirate as UART bridge worked fine. I could talk to the module and connect to my home WiFi via WPA2.
Last weeks EclipseCon Europe in Ludwigsburg, Germany was great! Thanks to all those active contributors, who made this event possible. Additional to the usual Java and Eclipse topics, there were very interesting sessions on the Internet of Things, web technologies, and OSGi.
A live demonstration of Docker providing a very flexible infrastructure for Eclipse RT applications. I recently had the chance to try out Docker and it is really amazing. If you are looking for a lightweight and highly flexible alternative to virtualization on Linux, try this!
All in all, with the great conference food, the entertainment with Circus Eclipse and the rock-band Cool Down, and the great speakers and participants, this is an event I am already looking forward to in 2015!