1. Using a light sensor with BBC micro:bit and MicroPython

    A light sensor is a small component with a particular characteristic: it is basically a resistor and its resistance decreases if the light is more intense. To use it with micro:bit we need to use one of the analogic ports. To build this circuit you will need a breadboard, 3 jumper wires, a 10k resistance and possibly a Kitronik breadboard kit.

    The project

    I wanted to realise a simple project where, depending on the light intensity captured by the light sensor, the micro:bit shows an image of the Sun if the light is intense and an image of the Moon if the light is less intense.

    Here is the complete circuit scheme:


    "Image Copyright © Kitronik"

    and here is a picture of the finished project I created:


    The source code I needed is available here:

    and as a demo I realised this small video:

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  2. Prototyping BBC micro:bit projects with Kitronik breadboard kit

    BBC micro:bit has a few IO pins that can be used to interact with external devices. The problem with the board is that it's not easy to connect the classic jumper wires (those that we normally connect to a breadboard) to the micro:bit, unless using a crocodile clip and being limited to just 3 pins.

    Kitronik breadboard kit solves this problem, offering an interface where the micro:bit can be plugged and all the pins are easily connectable to the breadboard using normal male/female jumper wires.

    I've built a very simple circuit following an example you can find on this manual https://www.kitronik.co.uk/pdf/5603_inventors_kit_for_the_bbc_microbit_tutorial_book.pdf


    To build the circuit you also need 4 male/female jumper wires and two buttons. All this circuit does is to connect the buttons to the micro:bit pins that relate to those buttons. Basically pressing those buttons is the same as pressing button A or button B on the micro:bit board. Here you can see the schema in detail:

    Screenshot 2016-02-0714.30.36

    I've also made a short video so that you can see it in action:

    And of course the source code is available too:

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  3. Using BBC MicroBit accelerometer with Python

    In these days I'm having a bit of fun with BBC MicroBit board and I'm learning how to use the different sensors available. The latest one I wanted to try was the accelerometer. The board can "sense" if you are moving it in any of the 3 dimensional axes: X, Y, Z. According to the documentation there are four methods available that can be used to get these values: microbit.accelerometer.get_values() will return you a tuple with all the 3 values, while  microbit.accelerometer.get_x()microbit.accelerometer.get_y()microbit.accelerometer.get_z() will give you the single values.

    The documentation on the official website doesn't explain much and for example I didn't even know what was the range of the values I can get back from these methods (by the way it's between -1024 and 1024), so I decided to play with the code directly and write a very simple example. The small example I wrote, shows a smile on the board display if you keep it straight and shows a sad face if you bend it.

    This is the result:

    and this is all the needed code of the application:

    In the next days I will try to play with more sensors and to publish other examples.

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  4. Using Python PyPy in a virtual environment

    Sometimes we need to test if our code also works with PyPy implementation of Python. Assuming you have already installed it in your system, first find out where it is installed:

    ``` {.lang:zsh .decode:true} ➜ ~ which pypy /usr/local/bin/pypy

    then you need **mkvirtualenv** to create a virtual environment that will
    use this runtime:
    ``` {.lang:zsh .decode:true}
    ➜  ~  mkvirtualenv -p /usr/local/bin/pypy pypy-test
    Running virtualenv with interpreter /usr/local/bin/pypy
    New pypy executable in pypy-test/bin/pypy
    Installing setuptools, pip, wheel...done.
    (pypy-test)➜  ~  python
    Python 2.7.10 (f3ad1e1e1d6215e20d34bb65ab85ff9188c9f559, Sep 01 2015, 06:26:30)
    [PyPy 2.6.1 with GCC 4.2.1 Compatible Apple LLVM 6.1.0 (clang-602.0.53)] on darwin
    Type "help", "copyright", "credits" or "license" for more information.

    That's it! You can now use this virtual environment to run your Python application using PyPy environment.

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