====== Variod ======
The Variod is a Linux program with the following functions:

  * Communication to XCSoar
  * User Interface for Volume Control and Tone Settings
  * Audio-Vario and Speed to Fly

The Variod obtains data from XCSoar and from the sensord. Have a look at the [[projects:series_00:build:audio_vario_speed_to_fly#general_operation_principle|General operation principle]] to understand the details. 

=====Internal Data Flow=====

**Sensors** --> [i2c bus] --> **sensord** --> [NMEA over TCP port 4353] --> **variod** --> [NMEA over TCP port 4352] <--> **XCSoar**

=====Command Line Options=====
Usually the Variod runs in the background as a daemon, but for special purposes it is possible to start variod with options. Here is a short overview about the possibilities:

<code>
variod  -v              print version information
variod  -f              don't daemonize, stay in foreground
variod  -c [filename]   use config file [filename]
variod  -d[n]           set debug level. n can be [1..2]. default=1
</code>

The sound characteristics of the Audio-Vario is defined in the default config-file: 

<code>
/opt/conf/variod.conf
</code>


The following parameters can be set according to your personal preferences:

===== Audio Vario Configuration =====

^ Name ^ Description ^ Unit ^ Example  ^
| Deadband Low         | The lower limit for the deadband of the audio vario.  |  m/s  |        -0.2     |
| Deadband High        | The upper limit for the deadband of the audio vario.  |  m/s  |        +0.5     |
| Pulse Length         | The length of the pulse generated by the vario synthesizer |  samples  |     12500    |
| Pulse Length Gain     | The gain the pulse length will be boosted if vario value increases  |     |       1.1     |
| Base Frequency Positive         | Frequency of the vario tone if vario value is positive  |  Hz  |       402     |
| Base Frequency Negative       | Frequency of the vario tone if vario value is negative  |  Hz  |       350     |

===== Speed to Fly Configuration =====

In preparation

===== Global Volume Control =====

Global settings of audio-parameters can be made using the **alsamixer** from the shell, a graphical program which is part of the OV-Linux-Kernel. We recommend to set the master gain to 100%. The settings can be saved with the command **alsactl store**.

===== NMEA Syntax =====

The Variod receives Commands from XCSoar using the following NMEA-strings:

^ NMEA-String ^  Description  ^ Unit  ^  Example  ^
|  POV   | Initial String for OpenVario   |    |             |
|  C   | Command Mode (XCSoar sends Pilot's Commands to Variod)  |    |            |
|  MC   | Mac Cready Value from XCSoar  |  m/s  |        1.2     |
|  WL    | Wing Load  | Factor  |        1.0 is with no ballast    |
|  BU    | Bugs (on the aerofoil)  |  %  |        10     |
|  POL  | Polar Coefficients a,b,c |    |   in preparation    |
|  VU    | Volume Up  |   |        in 10 steps    |
|  VD    | Volume Down  |   |        in 10 steps    |
|  VM    | Volume Mute  |   |    Toggle ON/OFF   |
|  VAR  | Set Vario Mode  |   |      VAR    |
|  STF  | Set Speed To Fly Mode  |   |     STF   |

The NMEA-strings above are for the Variod only, the complete information about all NMEA-strings used by Openvario can be found here:

[[nmea|NMEA-Definition]]

===== Volume Control during Flight =====

The corresponding User Interface in XCSoar can be found in Quick Menu -> Vario

{{:playground:electrical_tests:screen_variomenu.png?direct&500|}}

XCSoar Vario User Interface

The Audio Vario has to be activated in XCSoar. 

{{:projects:series_00:software:config-gauges-audiovario.jpg?500|}}


**Warning:** The sound configuration from XCSoar can be found at Config -> Gauges -> AudioVario, but it has **no effect** at all! At the moment the sound configuration has to be done by editing the file variod.conf manually, as described above.

{{:projects:series_00:software:gauges-audiovario.jpg?500|}}

===== Source Code Details =====

If you want to know what's inside the variod, you can use a git client to obtain the source code on your local computer. 

<code>
git clone http://git-ro.openvario.org/varioapp.git
</code>

Navigate to [[sensord]]

Go back to [[overview|Overview]]

Go to [[projects:series_00:build:audio_vario_speed_to_fly|Audio Vario / Speed to Fly]]

Go to [[projects:series_00:build:setupguide|Setup Guide]]