Description

The IMU Logger sample works with any serial port (UART) based IMU sensor or with the Xsens IMU device connected over USB. The logger requires the IMU sensor connected over serial port to deliver messages in NMEA format, while the Xsens device can run in proprietary mode.

Interfacing with sensors

Serial

Consumer grade off-the-shelve IMU sensors are usually connected over USB and implement a serial-to-USB connection with the help of FTDI devices. The Xsens IMU device can be connected through a serial-to-USB connection.

On Linux, these sensors can then be reached over the /dev/ttyUSB or /dev/ttyACM devices. Before trying out the sample, ensure the user has access to the serial device. You can do so by trying to read from the device e.g. with cat /dev/ttyACMx, and if permission is denied, add the current user to the dialout group and then log out/in again:

sudo usermod -a -G dialout $USER

On QNX, prior to accessing the device, launch the dev-serusb driver as follows:

devc-serusb -b <baudrate> -F -S -d path=/dev/usb/io-usb-otg

The serial devices can the be reached over the /dev/serusb devices.

Xsens USB

The Xsens IMU device can also be connected directly over USB, but is only supported on Linux.

Running the Sample

The sample requires the driver and name of the device of the IMU sensor.

The IMU Logger sample, sample_imu_logger, accepts the following parameters:

./sample_imu_logger --driver=[imu.virtual|imu.uart|imu.xsens|imu.novatel|imu.dataspeed|imu.xsensCan|imu.bosch|imu.continental|imu.custom]
                    --params=[comma/separated/key/value/pairs]
                    --timestamp-trace=[true|false]

Where:

--driver=[imu.virtual|imu.uart|imu.xsens|imu.novatel|imu.dataspeed|imu.xsensCan|imu.bosch|imu.continental|imu.custom]
    Allows to specify which IMU driver to use.
    Default value: imu.virtual

--params=[comma/separated/key/value/pairs]
    Different parameters are available for each IMU driver.
    Default value: file=path/to/data/samples/sensors/imu/imu.txt

--timestamp-trace=[true|false]
    Allows to output only the timestamp deltas between consecutive frames.
    Default value: false

Note: For a full list of key/value pairs that can be passed to –params see Sensor Enumeration Sample.

Examples

NMEA format

For serial devices transmitting messages in NMEA format, use the imu.uart driver. For example:

./sample_imu_logger --driver=imu.uart --params=device=/dev/ttyUSB0,baud=115200

Per default, if no baud parameter has been provided imu.uart driver assumes a baudrate of 9600. In order to change the baudrate provide baud argument as:

./sample_imu_logger --driver=imu.uart --params=device=/dev/ttyUSB0,baud=115200

On QNX, the baudrate is set when starting devc-serusb. The baud parameter will be ignored.

Xsens proprietary format

The sample supports reading IMU packets from a Xsens device through the imu.xsens driver. To run the sample using Xsens over USB device use:

./sample_imu_logger --driver=imu.xsens --params=device=0,frequency=100

Where device=0 parameter sets the index of the Xsens device (usually 0 if only one device is installed) and frequency=100 sets the frequency in [Hz] this device should operate with.

To run the sample using Xsens over serial use:

./sample_imu_logger --driver=imu.xsens --params=device=/dev/ttyUSB0,frequency=100

Please note that even if the Xsens device is a shared device, like Xsens MTi-G-700, capable of delivering GPS and IMU packets, only the IMU packets will be parsed by the imu.xsens driver.

Note: If the device is connected to Xavier UART you need also specify –stop-bits=1

Output

For every valid IMU message that the sample receives, it prints to the console data such as:

[7156364888] Heading(True:112.07)
[7156364959] Gyro(Z:0.0756667 )
[7156369081] Orientation(R:-1.3 P:-0.9 ) Gyro(X:-0.01 Y:-0.05 ) Heading(True:112.1)
[7156389724] Heading(Magnetic:112.07)
[1475788068778749] Heading(Magnetic:112.1)
[7156389797] Orientation(R:-1.31 P:-0.89 )
[1475788068778919] Orientation(R:-1.30529 P:-0.893047 Y:112.078 ) Gyro(X:0.0229183 Y:-0.0687549 Z:0.120321 ) Acceleration(X:-0.1398 Y:-0.2612 Z:9.7838 ) Magnetometer(X:7.18 Y:3.056 Z:-16.16 )

Where the first number indicates the timestamp of the received IMU message in microseconds and the rest of the line indicates the IMU information of the sensor.

Additional Information

For more details see IMU.

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