w-geronius/signalk-hwt901b-imu

SignalK node server plugin reading roll, pitch and course from WITMOTION's HWT910B IMU sensor

SignalK node server plugin (BETA) reading roll, pitch and magnetic heading from WITMOTION's HWT910B sensor

INPUT:

as of device data sheet and own testing, cable plug respresenting the boat's stern:
0x55 0x53 PitchL PitchH RollL RollH YawL YawH VL VH SUM

CALCULATION：

• Pitch (x axis):
  ((PitchH<<8)|PitchL)/32768*180(°)
• Roll (y axis):
  ((RollH<<8)|RollL)/32768*180(°)
• Yaw (z axis):
  ((YawH<<8)|YawL)/32768*180(°)
• Version：
  (VH<<8)|VL
• Checksum：
  SUM=0x55+0x53+RollH+RollL+PitchH+PitchL+YawH+YawL+VH+VL (least significant byte must match SUM)
• Magnetic Heading:
  z axis value (yaw) plus an offset determined after calibration and install

PROCESSING:

• Gyroscope has to be calibrated by wit motion windows software prior to final placement onboard
• acceleration calibration, as well as levelling pitch & roll can be accomplished via the plugin's settings:

OUTPUT TO SIGNALK (in rad):

{"updates":[{"$source":"WIT.n",
             "values":
               [{"path": "navigation.headingMagnetic",
                         "value":123.456},
                {"path": "navigation.attitude",
                         "value":{"roll":0.123456,
                         "pitch":-0.123456,
                         "yaw":null}}
                ]
            }]
}

signalk-hwt901b-imu's Issues

WIT z-output should not directly be interpreted as HDG

valuable contribution of Rolf, via eMail - many thanks

Wir beide haben den https://www.wit-motion.com/10-axis/witmotion-hwt901b-rs232-10.html bzw. https://www.wit-motion.com/10-axis/witmotion-hwt901b-ttl-10.html.
Schaut man sich die Beschreibung von witmotion-wt901c-ttl-9-axis-imu-sensor an, sieht man deutlich "Tilt" im Namen, bei uns fehlt diese Tiltkompensation.
Ich habe diverse Tutorials gefunden, die haarklein und von Anfang an erklären wie man die Werte berechnet indem die IMU (mag und gyro) ausgelesen wird. Ich denke aber das ist bei uns nicht nötig, da reicht die Anpassung mittels atan2 um die Tilt Anpassung zu bekommen. Dann sollte der Sensor auch in jeder Lage stabile Daten bereit stellen. Das wirst du auch in Java hinbekomnen.
https://www.youtube.com/watch?v=p_qZ-ie2R7o
Bei um die 25-30 min baut er das z.B. bei seinem Sensor ein.
Zumindest kannst du jetzt deine Doku ergänzen denn die Wit C Reihe wird die Probleme so nicht haben bzw. man müsste die Tilt-Anpassung aus deinem Modul da aus lassen.

WT901C

Hello, does the plugin work with the WT901C RS232 model? Thank you for your help !

horizontal/vertical install and test non standard mounting

It should be possible to set horizontal/vertical sensor orientation.
Effects require some more tests!

Also: possibly the sensor produces odd angles when mounted head down (i.e. different direction rotation )

negative angles

by applying a heading offset, it is possible to generate negative angles. Check log of 15.9. (heading offset was set to -10)
Also check impact of derived data corrections

plugin not working in Lysmarine SignalK

Hi, I try to use the plugin with SignalK in Lysmarine OS (bareboat necessities).
Plugin configured with /dev/ttyUSB0 port.
In logfile I get this error:
Oct 14 09:21:34 2022-10-14T09:21:34.855Z signalk-hwt901b-imu plugin.stop
Oct 14 09:21:34 2022-10-14T09:21:34.861Z signalk-hwt901b-imu plugin.connect
Oct 14 09:21:34 connecting to /dev/ttyUSB0:0
Oct 14 09:21:34 2022-10-14T09:21:34.869Z signalk-hwt901b-imu Plugin options saved
Oct 14 09:21:34 POST /skServer/plugins/signalk-hwt901b-imu/config 200 9.690 ms - 50
Oct 14 09:21:34 2022-10-14T09:21:34.877Z signalk-hwt901b-imu plugin.connect.close
Oct 14 09:21:34 TypeError: DelimiterParser is not a constructor at SerialPort. (/home/signalk/.signalk/node_modules/.pnpm/[email protected]/node_modules/signalk-hwt901b-imu/index.js:98:44) at SerialPort.emit (node:events:513:28) at binding.open.then.opening (/home/signalk/.signalk/node_modules/.pnpm/@serialport[email protected]/node_modules/@serialport/stream/lib/index.js:234:12)

Thanks for helping.

9-axis mode should be forced on plugin start

to ensure processing of magnetometer data, the sensor should be automatically set to 9-axis mode at every plugin start