========================
Playing with a Mind Flex
========================
:CreationDate: 2015-10-23 13:11:34
:Id: HW/mindflex
:tags: - hardware
       - software

Some time ago I bought a `Mind Flex`_, with the idea of interfacing it
to some motors, and control a thing **with my mind**!.

Of course it sat unused for years.

Then I got myself a `MicroView`_, because it was pretty.

Of course it, too, sat unused for years.

Today I finally put the two together.

.. _`Mind Flex`: http://store.neurosky.com/products/mindflex
.. _`MicroView`: http://learn.microview.io/Intro/general-overview-of-microview.html

Software setup
==============

First of all, I had to set up the Arduino IDE + compilers. On a Gentoo
system it's a bit tricky, but thanks to `a very clear post on the
Apollo NG site`_ I got it installed::

  emerge arduino crossdev dev-java/rxtx

  USE="multilib -cxx" crossdev -s1 --without-headers \
    --target avr \
    --gcc 4.5.4 --binutils 2.21.1-r1 --libc 1.7.0

  USE="multilib cxx" crossdev -s4 \
    --target avr \
    --gcc 4.5.4 --binutils 2.21.1-r1 --libc 1.7.0

  ln -nsf /usr/x86_64-pc-linux-gnu/avr/lib/ldscripts \
          /usr/avr/lib/ldscripts

  ln -nsf /usr/x86_64-pc-linux-gnu/avr/lib/ldscripts \
          /usr/x86_64-pc-linux-gnu/avr/binutils-bin/2.20.1/ldscripts

  cd /usr/avr/lib

  ln -nsf avr5/crtm328p.o .
  ln -nsf avr6/crtm2561.o .
  ln -nsf avr6/crtm2560.o .

.. _`a very clear post on the Apollo NG site`: https://apollo.open-resource.org/mission:log:2015:01:20:gentoo-crossdev-compile-avr-gcc-for-arduino-and-cura

Arduino libraries
-----------------

I needed two libraries: the one to `read the Neurosky EEG data`_, and
the one to `control the MicroView hardware`_.

I cloned them in my "sketchbook" directory::

  mkdir -p ~/sketchbook/libraries
  cd ~/sketchbook/libraries

  git clone git@github.com:geekammo/MicroView-Arduino-Library.git \
      MicroView

  git clone git@github.com:kitschpatrol/Brain

Note that the MicroView library needs to be in a folder called
``MicroView``, not ``MicroView-Arduino-Library``: the Arduino IDE
really dislikes dashes in library names.

.. _`read the Neurosky EEG data`: https://github.com/kitschpatrol/Brain
.. _`control the MicroView hardware`: https://github.com/geekammo/MicroView-Arduino-Library/

Hardware setup
==============

I followed the instruction at `Frontier Nerds`_, soldering a wire to
the "T" pin of the Neurosky board, one wire to ground, and (my
addition) one wire to battery "+". This way I can power the MicroView
from the same batteries as the Mind Flex: when I tried powering them
separately, the Neurosky board seemed to have serious difficulty
getting a signal, probably because of noise on the power line.

I then connected (currently via a small breadboard) the MicroView to
the wires: ground to pin 8, power to pin 16, signal to pin 9 (serial
receive).

.. _`Frontier Nerds`: http://www.frontiernerds.com/brain-hack

The program
===========

This is the very simple program I wrote::

  #include <MicroView.h>
  #include <Brain.h>

  // the MindFlex is connected to the serial input
  Brain brain(Serial);

  void setup() {
    // the MindFlex speaks 9600 bps
    Serial.begin(9600);
    // setup the MicroView display
    uView.begin();
    uView.clear(ALL);
    // use the smallest font, 5x7
    uView.setFontType(0);
  }

  const int hist_width=3;
  const int hist_pad=1;

  void loop() {
    if (brain.update()) { // do we have data to show?
      uView.clear(PAGE);

      // print the signal quality, 0=good, 200=no signal
      uView.setCursor(0,0); uView.print(brain.readSignalQuality());

      // print the two "high level" signals
      uView.setCursor(0,9); uView.print(brain.readAttention());
      uView.setCursor(18,9); uView.print(brain.readMeditation());

      // we then have 8 frequency bands
      const uint32_t* power = brain.readPowerArray();
      // find the maximum value, for scaling
      uint32_t max_value=0;
      for (int x=0;x<8;++x) {
        if (power[x] > max_value) {
          max_value = power[x];
        }
      }

      // draw a simple bar chart
      for (int x=0;x<8;++x) {
        int x0 = (hist_width + hist_pad) * x;
        // we have 30 vertical pixels
        int height = power[x] * 30 / max_value;
        for (int o=0;o<hist_width;++o) {
          uView.lineV(x0+o,47-height,height);
        }
      }

      // blit the buffer to the display
      uView.display();
    }
  }

And that's it.