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Some interesting stuff from the Seed studio site

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GrovePi+ a Raspberry Pi hat that breaks out connectors for grove contacts. I think grove is basically a standard where you get power in conjunction with every pin on the development board. So it could be digital, analog and so on.

0.5 Inch OLED display Arduino shield for the Arduino micro form factor

Base Shield V2 A shield hat breaks out connectors for grove contacts. I think grove is basically a standard where you get power in conjunction with every pin on inthis case an Arduino or Arduino compatible. So it could be digital, analog and so on.

Screw Shield sturdier connections

Grove - Loudness Sensor


Oct 13, 2016 10:15

GraphQL: A new API standard

Posted by admin |

GraphQL | A query language for your API

Looks interesting, as an alternative to REST or JSON-RPC.

Oct 12, 2016 01:26

How to convert a Google document into a presentation with CSS

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This trick uses pure CSS to make a Google document into a PDF slide presentation. Just export the doc to HTML and paste in the CSS code below.

What you will get

  • Title, heading 1 and heading 2 will be kept, and so will bulleted lists
  • Pretty much everything else gets hidden.
  • Each of title, heading 1 or heading 2 starts a new slide.
  • There will be a logo placed above each slide heading.

How to do it

Export your document to HTML

Open the HTML document and remove the style element inside the head element

Paste this style element in instead (it assumes your logo is in images/image00.png)

    <style type="text/css">
    p {
        display: none;
    body {
        font-family: sans-serif;
    p.title {
        display: block;
        font-weight: bold;
        font-size: 48px
    @media print {
        h2 {
            page-break-before: always;
            padding-top: 40mm
        h1 {
            font-size: 42px
        h2 {
            font-size: 36px
        h2 {
            background-image: url('./images/image00.png');
            background-repeat: no-repeat;
            background-position: left top


Open the html file in e.g. Google Chrome

Open print dialog

Make sure "Background graphics" is ticked if you are using Google Chrome

Print to PDF

Open PDF in PDF viewer

Choose Presentation mode

Oct 10, 2016 05:40

Hobbyist hardware for sensors, automation, smart devices, secure computing

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As a hobbyist as you are thinking of little projects to make, you start thinking about what is the right tool for the job: A Raspberry Pi, an Arduino, a Teensy, some kind of dedicated module?

I am not that experienced a hobbyist yet, but below I have tried to break down into four categories what categories my project plans or occasional actual project, tend to to end up in:

  • Wireless sensor
  • Smart device
  • Home automation
  • Secure computing

Wireless sensor


  • Should last on a battery for at least a year
  • Should communicate wirelessly


  • Arduino-compatible low power chip with lots of power saving features switched on, paired with Bluetooth LE
  • TI's SensorTag, can communicate via Bluetooth LE, 6LoWPAN or ZigBee


  • A humidity sensor for keeping indoor air from being to dry
  • Sensor to control a fan in a bathroom

Smart device


  • Can measure things, move things (actuators) and interact via a display with a user


  • Use an Android phone, it has built in Bluetooth, Wi-Fi, 3G, USB and a battery backup. Takes a whole lot of work to get that with discrete parts. Sometimes the headphone output can control a servo. otherwise put an amplifier there or use an USB OTG cable and firmata.


  • A bitcoin triggered lock box

Home automation


  • Can measure, control and communicate to the Internet


  • Use a laptop connected with an Arduino or similar connected to it via USB. The laptop has built in battery backup and Internet connectivity + keyboard and a display
  • Use an Android phone


  • Automation of watering house plants

Secure computing


  • Encrypt stuff, sign stuff, safeguard stuff


  • Use something like a Teensy3.5/3.6 or similar that has a cryptographic co-processor. An Arduino might suffice if you're doing simple things such as just inputting or outputting characters

What about the Raspberry Pi?

Interestingly enough the Raspberry Pi never featured in this when I started thinking about it. Capricious shutdowns may corrupt it's SD card which could take the system out of commission. It takes a number of additional components to make it have a rechargeable battery and a display. There are attempts to run Pis on their bare metal but it's hard to get good documentation on how the hardware works on that level apparently. It seems to work well for home entertainment though.

Oct 02, 2016 02:20

The new Teensy boards (v 3.5 & 3.6)

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Teensy 3.5 & 3.6 by Paul Stoffregen — Kickstarter

Teensy are Arduino compatible microprocessor boards with a bit more oomph than Arduino. The new Teensies run on an ARM processor and at clock speeds above 100 MHz, while still beeing teensy in size.

The new Teens boards have a dedicated cryptographic co-processor that according to the PDFs linked below supports acceleration of the DES, 3DES, AES, MD5, SHA-1, and SHA-256 algorithms. So basically cryptographic hasing (SHA-256) and symmetric crypto (AES).


From the kickstarter page:

Technical Features & Specifications

Features specific to Teensy 3.6:

  • 180 MHz ARM Cortex-M4 with Floating Point Unit
  • 1M Flash, 256K RAM, 4K EEPROM
  • Microcontroller Chip MK66FX1M0VMD18 (PDF link)
  • USB High Speed (480 Mbit/sec) Port
  • 2 CAN Bus Ports
  • 32 General Purpose DMA Channels
  • 22 PWM Outputs
  • 4 I2C Ports
  • 11 Touch Sensing Inputs

Features specific to Teensy 3.5:

  • 120 MHz ARM Cortex-M4 with Floating Point Unit
  • 512K Flash, 192K RAM, 4K EEPROM
  • Microcontroller Chip MK64FX512VMD12 (PDF link)
  • 1 CAN Bus Port
  • 16 General Purpose DMA Channels
  • 5 Volt Tolerance On All Digital I/O Pins

Features common to both:

  • 62 I/O Pins (42 breadboard friendly)
  • 25 Analog Inputs to 2 ADCs with 13 bits resolution
  • 2 Analog Outputs (DACs) with 12 bit resolution
  • 20 PWM Outputs (Teensy 3.6 has 22 PWM)
  • USB Full Speed (12 Mbit/sec) Port
  • Ethernet mac, capable of full 100 Mbit/sec speed
  • Native (4 bit SDIO) micro SD card port
  • I2S Audio Port, 4 Channel Digital Audio Input & Output
  • 14 Hardware Timers
  • Cryptographic Acceleration Unit
  • Random Number Generator
  • CRC Computation Unit
  • 6 Serial Ports (2 with FIFO & Fast Baud Rates)
  • 3 SPI Ports (1 with FIFO)
  • 3 I2C Ports (Teensy 3.6 has a 4th I2C port)
  • Real Time Clock
Oct 01, 2016 11:05

Running scripts with passwordless sudo

Posted by admin |

Quoted from the page  (Ubuntu ):

Shutting Down From The Console Without A Password

Often people want to be able to shut their computers down without requiring a password to do so. This is particularly useful in media PCs where you want to be able to use the shutdown command in the media centre to shutdown the whole computer.

To do this you need to add some cmnd aliases as follows:

Cmnd_Alias SHUTDOWN_CMDS = /sbin/poweroff, /sbin/halt, /sbin/reboot

You also need to add a user specification (at the end of the file after the "%admin ALL = (ALL) ALL" line so it takes effect - see above for details):


Obviously you need to replace "<your username>" with the username of the user who needs to be able to shutdown the pc without a password. You can use a user alias here as normal.


Read more: Link - Sudoers - Community Help Wiki

Oct 01, 2016 10:17

If your Acer Aspire V-573G is hard to start

Posted by admin |

That is, when you depress the start button on the left hand side, it sometimes has problem starting up, especially when not connected to mains, then in my experience you may need to get a new CR2032 battery on the mother board.

  • Remove the screws on the underside of the laptop
  • Pop off the bottom
  • Locate the battery (it's in the center)
  • Pop it out
  • Replace it with a new one

You should be grounded and it may be a good idea to disconnect the battery (the big one, not the coin cell we are talking about in this blog post) from the motherboard before beginning. The old CR2032 battery had a voltage of 2.94V as measured and a new one 3.04V. So maybe it started working better for another reason, or that difference is enough. Maybe the old one had an even lower voltage under load.

Sep 27, 2016 05:35

"Oh Snap!" in Chrome and crashing Firefox: SSD or Ubuntu 16.04?

Posted by admin |

One of my computers has for some time had the problem that tabs in Chrome get the "Oh snap!" message after a while, and Firefox just crashes mysteriously after many hours. This computer runs Ubuntu 16.10 and has an M2 SSD. Now my laptop is showing exactly the same behaviour, after having had an SSD installed.

I wonder if this is because the hardware isn't up to handling the speed of the SSD drives or if there is some kind of conflict between the SSD and the OS. I will slow down the SSD bus speed on the laptop and see if that helps.

Update 2016-12-31:

It helped!


Sep 20, 2016 10:55