NMEA 0183 Wind Vane¶
NMEA 0813 is a widely used maritime standard, this driver makes used of the MWV message this is used by many wind sensors sold for use on full-size sailboats. This example shows a Calypso Wired Standard anemometer this is a ultrasonic anemometer that provides acuate wind speed and direction in a small package. Typically ultrasonic anemometers are more acuate than traditional wind vanes, particularly in low wind speeds.
The NMEA driver can be selected by setting WNDVN_TYPE to 4 and/or WNDVN_SPEED_TYPE to 4. The driver uses a serial port, the selected seral port’s protocol should set to type 21 for WindVane. For use with a wind vane the WNDVN_DIR_OFS parameter can be set to account for any offset between the wind vanes’ forward direction that of the vehicle. Electrical connection is slightly more complex as NMEA 0183 uses a RS-422 signal. Commercial RS-422 to ttl logic level converters designed for use with NMEA will make this connection easy however, they can be costly. It is possible to use a RS-233 converter with most NMEA devices, these are much more readily available. This example shows a MAX3232 based transceiver board from SparkFun, for use with a expensive device such as a wind vane it is recommended to buy from a reputable supplier, clone MAX3232 are common. Note than the wire colors in the diagram may not match your device.
Although not required for normal operation on some NMEA devices have receive inputs, these can be connected to the flight controller via the logic translator. This allows ArduPilot to act as a NMEA to USB adapter for use with the manufacturers tools for updating the wind vanes’ firmware or configuration.