IMU Command

Tag 0x30-0x3f command for Inertial measurement unit (IMU) are explained in this page.

Keyword

NA: Not applicable, this command should no be sent by the sensor/application.

None: No data contained in this command, data length can be set to 0x00.

Tag 0x30

Meaning:
Start recording from IMU. Recording continue until user call the stop recording command tag 0x31. Data replay from IMU will use tag 0x36-0x39.

Data format - app send:

Byte Length 1 1 1 1 1
Meaning Accel ODR Accel FS Gyro ODR Gyro FS Reply Format

Output Data Rate (ODR), Full Scale (FS) and reply format code listed below.

Accel ODR / Hz code Accel FS / +-g code
6777 0x0a 16 0x01
3333 0x09 8 0x03
1667 0x08 4 0x02
833 0x07 2 0x00
416 0x06
208 0x05
104 0x04
52 0x03
26 0x02
12.5 0x01
1.6 0x0b
OFF 0x00
Gyro ODR / Hz code Gyro FS / +-dps code
6777 0x0a 2000 0x03
3333 0x09 1000 0x02
1667 0x08 500 0x01
833 0x07 250 0x00
416 0x06
208 0x05
104 0x04
52 0x03
26 0x02
12.5 0x01
OFF 0x00

Magnetometer ODR and FS is auto selected by the setting of Accelerometer and Gyroscope.

Magnetometer only turn on when both Accel ODR and Gyro ODR are ON.

Reply data format code reply tag tag info
Accel, Gyro and Mag 0x01 0x36 here
Accel, Gyro and Mag with time stamp 0x02 0x36 here
Quaternion 6x 0x03 0x37 here
Quaternion 6x with time stamp 0x04 0x37 here
Quaternion 9x 0x05 0x38 here
Quaternion 9x with time stamp 0x06 0x38 here
Quaternion 9x with Accel value and time stamp 0x07 0x39 here

IMU must not working on other mode when call this command.

Data format - app receive:

Same as send format. Same format acknowledge after command is executed.

Tag 0x31

Meaning:
Stop recording from IMU.

Data format - app send:
None

Data format - app receive:

Same as send format. Same format acknowledge after command is executed.

Tag 0x32

Meaning:
Set IMU offset. (On development...)

Data format - app send:

Byte Length 16 (optional)
Meaning Offset Quaternion

Offset Quaternion: contains 4 Float value, 4 bytes each, in the order of X Y Z W, represent the quaternion offset. All zero or no offset given means remove the current offset.

When starting a new IMU data streaming with 6x or 9x quaternion format, sensor will load the last offset from save on default.

Data format - app receive:

Same as send format. Same format acknowledge after command is executed.

Tag 0x36

Meaning:
Reply IMU data in accelerometer(ms^-2) and gyroscope(degree/s) value format.

Data format - app send:
NA

Data format - app receive:

Byte Length 12 12 12 8 (optional)
Meaning Accel Value Gyro Value Mag value Time Stamp

Accel Value: Float format, accelerometer(g) X, Y, Z axis value, each axis has 4 bytes length. Can be turn off by setting the ODR to 0x00.

Gyro Value: Float format, gyroscope(degree/s) X, Y, Z axis value, each axis has 4 bytes length. Can be turn off by setting the ODR to 0x00.

Mag Value: Float format, magnetometer(mGauss) X, Y, Z axis value, each axis has 4 bytes length. Only available when both accelerometer and gyroscope turn on. ODR and FS are auto selected.

Time Stamp: Unsigned Long, unit is 2.4414us. Represent the data record time. Only appear when the "with time stamp" format is chosen. Pay attention that this value might not start from zero. Usually it is used to help synchronize data from multiple sensors or calculate the accurate data rate.

Tag 0x37

Meaning:
Reply IMU data in quaternion data format. 6 axis (accel + gyro) are used to calculate the quaternion value.

Data format - app send:
NA

Data format - app receive:

Byte Length 16 8 (optional)
Meaning Quaternion Time Stamp

Quaternion: contains 4 Float value, 4 bytes each, in the order of X Y Z W, represent the rotation axis and angle of the sensor.

Time Stamp: Unsigned Long, unit is 2.4414us. Represent the data record time. Only appear when the "with time stamp" format is chosen. Pay attention that this value might not start from zero. Usually it is used to help synchronize data from multiple sensors or calculate the accurate data rate.

Tag 0x38

Meaning:
Reply IMU data in quaternion data format. 9 axis (accel + gyro + mag) are used to calculate the quaternion value.

Data format - app send:
NA

Data format - app receive:

Byte Length 16 8 (optional)
Meaning Quaternion Time Stamp

Quaternion: contains 4 Float value, 4 bytes each, in the order of X Y Z W, represent the rotation axis and angle of the sensor.

Time Stamp: Unsigned Long, unit is 2.4414us. Represent the data record time. Only appear when the "with time stamp" format is chosen. Pay attention that this value might not start from zero. Usually it is used to help synchronize data from multiple sensors or calculate the accurate data rate.

Tag 0x39

Meaning:
Reply IMU data in quaternion with Accel value data format. 9 axis (accel + gyro + mag) are used to calculate the quaternion value.

Data format - app send:
NA

Data format - app receive:

Byte Length 12 16 8
Meaning Accel Value Quaternion Time Stamp

Accel Value: Accelerometer(g) value separated in X, Y, Z axis, each axis has 4 bytes, all in Float format.

Quaternion: contains 4 Float value, 4 bytes each, in the order of X Y Z W, represent the rotation axis and angle of the sensor.

Time Stamp: Unsigned Long, unit is 2.4414us. Represent the data record time. Only appear when the "with time stamp" format is chosen. Pay attention that this value might not start from zero. Usually it is used to help synchronize data from multiple sensors or calculate the accurate data rate.

Tag 0x3A

> Meaning:

Start IMU record in storage.

> Data format - Input:

Byte Length 1 1 1 1 1 1 1 8
Meaning Accel ODR Accel FS Gyro ODR Gyro FS Reply Format Reset Stop Adv Current Unix Time

ODR and FS are the same as tag 0x30.

Reply data format code
Accel, Gyro and Mag Storage 0x00
Quaternion 6x Storage 0x01
Quaternion 9x Storage 0x02

Reset: If 0x01, all old records will be covered. If 0x00, old records keep, new data continue stored at the remaining storage space.

Stop Adv: Stop Advertising Code. If 0x01, BLE advertising stop during recording for power saving, advertising reactivate on charging. If 0x00, advertising continue during recording.

Current Unix Time: Input the current Unix Time in second, in format of 8 bytes, for recording date and time calculation. If not use, can be entered as 0.

IMU must not working on other mode when call this command.

Sensor auto disconnect and start recording after this command. Please wait for disconnect and don't send any other command after this command.

For data reading, refer to the [Storage](storage.md#tag-0x40) command page.

> Data format - Output:

Same as send format. Same format acknowledge after command is executed.

Tag 0x3B

> Meaning:

Stop IMU record in storage.

> Data format - Input:

Byte Length 8
Meaning Current Unix Time

Current Unix Time: Input the current Unix Time in second, in format of 8 bytes, for recording date and time calculation. If not use, can be entered as 0.

> Data format - Output:

Same as send format. Same format acknowledge after command is executed.