IMU Rotation Vector

This example shows rotation vector output at 400 hz rate using the onboard IMU. Returns quaternion.

Demo

Example script output

~/depthai-python/examples$ python3 imu_rotation_vector.py
Rotation vector timestamp: 0.000 ms
Quaternion: i: 0.089355 j: 0.355103 k: 0.034058 real: 0.929932
Accuracy (rad): 3.141602
Rotation vector timestamp: 3.601 ms
Quaternion: i: 0.088928 j: 0.354004 k: 0.036560 real: 0.930298
Accuracy (rad): 3.141602
Rotation vector timestamp: 6.231 ms
Quaternion: i: 0.094604 j: 0.344543 k: 0.040955 real: 0.933105
Accuracy (rad): 3.141602

Setup

Please run the install script to download all required dependencies. Please note that this script must be ran from git context, so you have to download the depthai-python repository first and then run the script

git clone https://github.com/luxonis/depthai-python.git
cd depthai-python/examples
python3 install_requirements.py

For additional information, please follow installation guide

Source code

Python

C++

Also available on GitHub

#!/usr/bin/env python3

import cv2
import depthai as dai
import time
import math

device = dai.Device()

imuType = device.getConnectedIMU()
imuFirmwareVersion = device.getIMUFirmwareVersion()
print(f"IMU type: {imuType}, firmware version: {imuFirmwareVersion}")

if imuType != "BNO086":
    print("Rotation vector output is supported only by BNO086!")
    exit(1)

# Create pipeline
pipeline = dai.Pipeline()

# Define sources and outputs
imu = pipeline.create(dai.node.IMU)
xlinkOut = pipeline.create(dai.node.XLinkOut)

xlinkOut.setStreamName("imu")

# enable ROTATION_VECTOR at 400 hz rate
imu.enableIMUSensor(dai.IMUSensor.ROTATION_VECTOR, 400)
# it's recommended to set both setBatchReportThreshold and setMaxBatchReports to 20 when integrating in a pipeline with a lot of input/output connections
# above this threshold packets will be sent in batch of X, if the host is not blocked and USB bandwidth is available
imu.setBatchReportThreshold(1)
# maximum number of IMU packets in a batch, if it's reached device will block sending until host can receive it
# if lower or equal to batchReportThreshold then the sending is always blocking on device
# useful to reduce device's CPU load  and number of lost packets, if CPU load is high on device side due to multiple nodes
imu.setMaxBatchReports(10)

# Link plugins IMU -> XLINK
imu.out.link(xlinkOut.input)

# Pipeline is defined, now we can connect to the device
with device:
    device.startPipeline(pipeline)

    def timeDeltaToMilliS(delta) -> float:
        return delta.total_seconds()*1000

    # Output queue for imu bulk packets
    imuQueue = device.getOutputQueue(name="imu", maxSize=50, blocking=False)
    baseTs = None
    while True:
        imuData = imuQueue.get()  # blocking call, will wait until a new data has arrived

        imuPackets = imuData.packets
        for imuPacket in imuPackets:
            rVvalues = imuPacket.rotationVector

            rvTs = rVvalues.getTimestampDevice()
            if baseTs is None:
                baseTs = rvTs
            rvTs = rvTs - baseTs

            imuF = "{:.06f}"
            tsF  = "{:.03f}"

            print(f"Rotation vector timestamp: {tsF.format(timeDeltaToMilliS(rvTs))} ms")
            print(f"Quaternion: i: {imuF.format(rVvalues.i)} j: {imuF.format(rVvalues.j)} "
                f"k: {imuF.format(rVvalues.k)} real: {imuF.format(rVvalues.real)}")
            print(f"Accuracy (rad): {imuF.format(rVvalues.rotationVectorAccuracy)}")


        if cv2.waitKey(1) == ord('q'):
            break

Also available on GitHub

#include <cstdio>
#include <iostream>

#include "utility.hpp"

// Includes common necessary includes for development using depthai library
#include "depthai/depthai.hpp"

int main() {
    using namespace std;
    using namespace std::chrono;

    // Create pipeline
    dai::Pipeline pipeline;

    // Define sources and outputs
    auto imu = pipeline.create<dai::node::IMU>();
    auto xlinkOut = pipeline.create<dai::node::XLinkOut>();

    xlinkOut->setStreamName("imu");

    // enable ROTATION_VECTOR at 400 hz rate
    imu->enableIMUSensor(dai::IMUSensor::ROTATION_VECTOR, 400);
    // it's recommended to set both setBatchReportThreshold and setMaxBatchReports to 20 when integrating in a pipeline with a lot of input/output connections
    // above this threshold packets will be sent in batch of X, if the host is not blocked and USB bandwidth is available
    imu->setBatchReportThreshold(1);
    // maximum number of IMU packets in a batch, if it's reached device will block sending until host can receive it
    // if lower or equal to batchReportThreshold then the sending is always blocking on device
    // useful to reduce device's CPU load  and number of lost packets, if CPU load is high on device side due to multiple nodes
    imu->setMaxBatchReports(10);

    // Link plugins IMU -> XLINK
    imu->out.link(xlinkOut->input);

    dai::Device d(pipeline);

    auto imuQueue = d.getOutputQueue("imu", 50, false);
    auto baseTs = steady_clock::now();

    while(true) {
        auto imuData = imuQueue->get<dai::IMUData>();

        auto imuPackets = imuData->packets;
        for(auto& imuPacket : imuPackets) {
            auto& rVvalues = imuPacket.rotationVector;

            auto rvTs = rVvalues.getTimestampDevice() - baseTs;
            printf("Rotation vector timestamp: %ld ms\n", static_cast<long>(duration_cast<milliseconds>(rvTs).count()));

            printf(
                "Quaternion: i: %.3f j: %.3f k: %.3f real: %.3f\n"
                "Accuracy (rad): %.3f \n",
                rVvalues.i,
                rVvalues.j,
                rVvalues.k,
                rVvalues.real,
                rVvalues.rotationVectorAccuracy);
        }

        int key = cv::waitKey(1);
        if(key == 'q') {
            return 0;
        }
    }

    return 0;
}

Got questions?

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