The sensord is a Linux Daemon program to interface the SensorBoard to XCSoar using NMEA Sentences

• Height - static pressure (MS5611)
• Vario - TEK pressure (MS5611)
• Speed - differential pressure (AMS5915)
• Battery Voltage (ADS1110 or ADS 1100 on the Adapterboard)
• Temperature (DS18B20)
• Acceleration (MPU 9150)
• Gyroscope (MPU 9150)

The measured values are processed by sensord and sent to variod and finally to XCSoar using NMEA data sentences. Here is an Overview about the General operation principle.

Sensors –> [i2c bus] –> sensord –> [NMEA over TCP port 4353] –> variod –> [NMEA over TCP port 4352] ←→ XCSoar

    -v              print version information
    -c [filename]   Config file for sensor compensation
    -d[n]           set debug level. n can be [1..2]. default=1
    -r [filename]   record measurement values to file
    -p [filename]   use values from file instead of measuring
    -s use second order temperature compensation for MS5611

The default configuration file is /opt/conf/sensord.conf

#Section for static pressure sensor
# Unit: Pa
#format: static_sensor [offset] [linearity]
#Example: static_sensor 1.5 1.3
static_sensor 0.0 1.0

#Section for tek pressure sensor
# Unit: Pa
#format: tek_sensor [offset] [linearity]
#Example: tek_sensor 1.5 1.3
tek_sensor 0.0 1.0

#Section for dynamic pressure sensor
# Unit: Pa
#format: dynamic_sensor [offset] [linearity]
#Example: dynamic_sensor 1.5 1.3
dynamic_sensor 0.0 1.0

#Output value config
output_POV_E
output_POV_P_Q
output_POV_V

#Vario parameter
#format:  vario_config [x_accel]
vario_config 0.3

#Voltage Sensor parameter
#format:  voltage_config [division_factor]
voltage_config 736

The default values for the Voltage Sensor are:

• voltage_config 736 for ADS1100 (External reference 3.3 V)
• voltage_config 1200 for ADS1110 (Internal reference 2.048 V)

The sensor readings can be compensated using two values. The values are stored in a file for the moment. For a future version the values should be stored in the EEPROM on the sensor board, because they are dependent on the sensors mounted on the board. This will improve the interchangeability on board level.

Automatic Differential Pressure Calibration

P = linearity * P_meas + offset

P         = final calculated pressure
P_meas    = pressure measured from sensor
linearity = correction factor for linearity
offset    = correction factor for offset 

Values are floating point decimal.

The full range of NMEA-strings used by the Openvario-Project can be found here: NMEA-Definition

The source code of the whole program is hosted in a git repository. To clone the repository, use the following command:

git clone http://git-ro.openvario.org/sensord.git

Navigate to variod

Go back to Overview

Go to Setup Guide