Tinkering with Raspberry (and other things)

Tiny Word Clock with Attiny85

The “Hello World” of microcontroller projects undoubtedly is a clock. As this was my first try with an Attiny85 I decided to build a tiny version of my big living room word clock (which is 40 x 40 cm) and put it into an IKEA picture frame.
I have been using an 8×8 LED-matrix (WS218b, Adafruit Neopixel compatible) and the first challenge was to get the German words for the different times into this 64 positions. The source code is heavily based on Adafruits tutorials. Continue reading

Elevator Information Display using two ILI9341 TFTs

It has been a long time since my last post, well, I have been busy and had significantly less time for tinkering.

But back again. Take an old elevator panel, two displays and a Raspberry Pi and transform it into a home information system.

Ingredients and Original Idea

  • A really old but massive elevator panel with all the original wiring, the buttons and even the led-matrix displays.
  • A Raspberry Pi (of course)
  • Two ILI9341 2.2″ TFT panels
  • Adafruit’s python library for ILI9341

My original idea was to reuse the LED-matrix from the old panels to display some information. This unfortunately was not possible as these are not ‘normal’ matrix displays but do have some sort of logic built in. Applying a voltage on the terminals (in the middle of the picture) does display the preprogrammed floor numbers in the display. Well, this is not a big issue, TFT displays are much cooler.
Here is an image of the unaltered elevator panel:original elevator panel

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Mac OS – El Capitan bluetooth discoverabilty

I recently upgraded my Mid 2011 Mac Mini to El Capitan and had to discover that when Bluetooth was switched on, the machine stayed discoverable via Bluetooth. Living in the middle of a big city this is a gerat security risk. I just don’t want everybody in the neighborhood to be able to see my Mac.

There are numerous instructions on the internet on how to disable the bluetooth visiblity via terminal commands (e.g. at but none of that did work. So I decided on checking the alternatives. And succeeded, thus this blog post. Continue reading

Making an eGalax/Pollin touchscreen work with tslib

Some months ago I found a cheap 7″ LCD screen with a resistive touch-panel. Searching the internet gave me some hope that the screen would work perfectly with my RaspberryPi. And alas, it did. Under XWindows, which I wasn’t going to use on the project I had in mind when buying the touch-display. So the search began and lastet. There’s lots of information out there about eGalax-touchscreens, most of it stating that one needs to compile a custom kernel, hack into some outdated driver software and so on.

After some investigation it became clear that the information available is mostly outdated, as the newer Raspbian images do recognize the touchscreen without compiling a custom kernel. So I started on my own and tried to get the screen working not with XWindows, but directly with the framebuffer. Continue reading

Quicktip: Selfmade LED lamp with T5.5 socket (Telephone Lamp)

For my newest project, the “intelligent desk clock” (I shortly mentioned it at the end of the last post) I need to have big momentary switches that could be illuminated. The idea is to let the switch blink if there is user interaction needed.

I found some switches that need old-style bulbs with “telephone lamp” socket, technically a “T5.5” or “T5.5k” socket. These are usually bulbs running at 12V or higher. I want to realize the project with an Arduino or a Raspberry Pi, so 5V is the voltage I have available. LED lamps with T5.5 socket are rather expensive, luckily I was able to order 10 pieces for 7 EUR from ebay. They do have red LEDs but I thought I could desolder them and solder some white ones to the socket.

Today I found some cool switches at my electronics shop, immediately purchased a bunch and at home, was able to completely disassemble the switch. So I now am able to put some label behind the orange button! Of course the shop had the fitting bulbs in stock, with real lamps rated at 12V, but for 0.5EUR a piece. So I took some, too.

Here are pictures of the switch and the disassembled parts:


Make your own T5.5 LED lamp

Take a look at the T5.5 lamp from the shop. It’s just a metal socket an the bulb soldered to it. The metal parts are glued to the bulb with tiny spots of some hot glue. With the help of a scalpel and some brave cutting and bending (watch your fingers if the glass breaks) the bulb can be detached from the metal socket. With a firm pull the whole bulb can be teared off. Now take a soldering iron and clean the soldering spots and, using the scalpel, clean the glue residue from the socket.

Shorten the wires on the LED (remember which side is Anode and Cathode, respectively) and the resistor (I used 220 Ohms, the usual value when using 5V and an LED). Solder the resistor to one wire on the LED and bend the wires slightly outward so they will make contact with the metal socket when fitted in. (One square of the paper is 5mm x 5mm)


Now fit the LED into the socket so that the socket is just around the bottom of the LED. You will need some sort of fixation tool like alligator clamps to make your life easier. Now cautiously solder the wires to the socket and you’re done. You should end up with something like this:


You will definitely need all your patience making this LED thingy. Taken into account that an LED lamp with T5.5 socket will cost around 5EUR (6 USD) each, it’s worth the effort.

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GPRS/GSM via Serial (again)

I recently stumbled over a cheap GPRS/GSM shield made for the Arduino platform, of course on ebay, of course from China. As it was priced at a very reasonable 20 EUR (25 USD), I thought I’d go with the risk and order from China. Several weeks later it finally arrived and, I couldn’t believe that at first, worked out of the box.

This is how it looks. If you get interested in one of these gadgets, just search for “GSM Arduino” on ebay, that should do the trick.


It’s a SIM900 based design and has a real time clock (plus buffer battery) on the back. A full description of all the possible AT-commands can be found here. It is basically the same shield that can be bought from Seedstudio, but much cheaper. A description with some sample sourcecode (that is working!) can be found at the Geeetech-Wiki pages. Continue reading


132 LED-matrix with AS1130 and Python

The AMS AG (austriamicrosystems) does have a neat little (literally) chip called AS1130 on the market. This chip is able to drive 132 LEDs, arranged in a 12×11 cross-plexed matrix. It can store up to 36 individual frames (pictures) and up to 6 patterns for blinking and PWM control of every single LED in every single frame. The frames can be displayed as still images or as a movie, the chip even scrolls the frames without the need for doing any calculations on the controlling computer side.
I could not find any Python code for that chip so I dived into the datasheet and wrote my own driver. As always, the sources are available via GitHub. Here is a short video demonstrating the capabilities of that chip. I had to use some paper to shield the ultra-bright LEDs or the camera would have recorded just a bright white spot…

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Pi-Hicle part 4 – Sensor Phalanx

I finally had the time to do some more work on my Raspberry Pi controlled Big Trak. So this is all about sensing the environment, well, avoiding obstacles, that is.

My idea is to have the vehicle measure the distance to any obstacles in front and to both sides. If it can’t move any further in forward direction, it will be turned in the direction (left or right) where there is the biggest distance to any obstacles. Very simple but that should be very effective. And it gives the impression of “real autonomy”, because the vehicle will turn in different directions to avoid a collision.

To get this done I ordered three Sharp GP2Y0A02YK0F distance sensors. They are well documented and used by many people out there, so I thought they should do for me, too. The sensors translate the distance into a voltage, so there is an analog value to be mapped to the distance. There is a data sheet with a nice graph showing the expected output voltage oder distance. According to the specifications the sensor has a range of 20 to 150 cm. That quickly proved to be a little too optimistic… Continue reading


Pi-Hicle part 3 – Big Trak autopsy and findings

This part is about the internals of the 2010 model “Big Trak”. I intend to use this toy as a base for my raspberry Pi powered vehicle. In part 1 of this series I covered the basic idea of my “Pi-Hicle” and recreated the Big Trak logic in Python. Part 2 was about displaying the programmed path on a display. Now I am lucky, because the “best girlfriend ever” gave me a real 2010 Big Trak for christmas. She even made a label, reading “Present for disassembly”. So I am doing nothing wrong here…

There are numerous resources out there about disassembling the Big Trak models, so I won’t cover this. Locate the screws and pay attention for those hidden under the grey rear bumper, then lift the top carefully and continue. David Cook from “The Robotroom” ( has extensive material about the original 198x Big Trak. For the new series of Big Traks you can find modding instructions with lots of pictures at srimech’s blog and some analysis of the circuits at the “Singleton Miller Wiki“. I am going to concentrate on my additional findings in this blog post. Nevertheless, here’s a quick overview where the screws are located. Blue arrows are “visible” screws, the red arrows point to where the additional screws are hidden under the bumper thingie:


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Pi-Hicle part 2 – Programming Movement And Display Path On Screen

In part one everything was about getting that legacy touch screen to work. Now it’s time to re-live my childhood. I am going to include the logic that will move my Pi-Hicle around.

In case you didn’t read the first part, here’s a short video demonstrating the GUI and screen output. The path can be programmed and will be displayed on screen with triangles showing the Pi-Hicle’s heading.

orientationThe original Big Trak was able to hold 16 instructions in its memory. Sixteen! With the Raspberry Pi as a brain this number is significantly higher, although not really needed. The programming was done with a touch pad where one could select the direction (forward, back, left, right), wait and fire. Every command was followed by one or two digits, telling the vehicle how many units of its own length to move. The numbers after the “left” and “right” instructions were used to program a turn if xx degrees. To make things easy for us children, the angle to move was scaled according to an analogue clock. 15 meant 90 degrees, 30 was 180 etc.

From the image it is clear that “Right-45” would have exactly the same effect as “Left-15”, although the vehicle would be rotating in the opposite direction. Continue reading