Examples for OpenZen Usage

Basic examples

For connecting to a single sensor, toggling sensor settings and output sensor data, please refer to Getting Started with OpenZen. If you prefer to study and run a full code example, please have a look at this example source file.

Connecting multiple Sensors

Its possible to connect multiple sensors with one OpenZen instance and event loops. Simply connect to multiple sensors and store the sensor’s handle:

auto sensorPairA = client.obtainSensorByName("SiUsb", "lpmscu2000574", 921600);
auto& sensorA = sensorPairA.second;

auto sensorPairB = client.obtainSensorByName("SiUsb", "lpmscu2000573", 921600);
auto& sensorB = sensorPairB.second;

In your event loop, now check which sensor the last received event is orginating from:

auto event = client.waitForNextEvent();

if (sensorA.sensor() == event.second.sensor) {
    std::cout << "Data from Sensor A" << std::endl;
} else if (sensorB.sensor() == event.second.sensor) {
    std::cout << "Data from Sensor B" << std::endl;
}

Synchronizing multiple Sensors

If multiple sensor are connected to the same OpenZen instance, they can be synchronized by putting them into synchronization mode and then sending the command to leave synchronization mode at the same time. The result of this operation will be that the timestamp and frameCount values returned by each sensor will be in the same time frame. However, this method is a software synchronization and does not account for the delay of the transport layer (USB, Bluetooth etc.) so the accuracy of this synchronization is limited by this fact. In our experience, the software synchronization can achieve a synchronization better than 5 milliseconds.

C++ example code:

// set both sensors in synchronization mode
imu_component1.executeProperty(ZenImuProperty_StartSensorSync);
imu_component2.executeProperty(ZenImuProperty_StartSensorSync);

// wait a moment for the synchronization commands to arrive
std::this_thread::sleep_for(std::chrono::seconds(3));

// set both sensors back to normal mode
imu_component1.executeProperty(ZenImuProperty_StopSensorSync);
imu_component2.executeProperty(ZenImuProperty_StopSensorSync);

// start receiving regular events from the sensors

Python example code:

# set both sensors in synchronization mode
imu_component1.execute_property(openzen.ZenImuProperty.StartSensorSync)
imu_component2.execute_property(openzen.ZenImuProperty.StartSensorSync)

# wait a moment for the synchronization commands to arrive
time.sleep(3)

# set both sensors back to normal mode
imu_component1.execute_property(openzen.ZenImuProperty.StopSensorSync)
imu_component2.execute_property(openzen.ZenImuProperty.StopSensorSync)

# start receiving regular events from the sensors

Manual Gyroscope Calibration

LPMS sensors include an advanced automatic calibration for the gyroscope bias during the operation of the sensor. This calibration model will detect if the sensor is at rest and automatically recalibrate the gyroscope bias without any user intervention. This mode is suited well for most application areas.

However, in some application domains controlling the gyroscope bias calibration manually can provide better results. Two examples are:

• The sensor is in constant motion so the automatic calibration will never be able to start.
• Slow and steady moving platforms might make the automatic calibration start even if the platform is actually not at rest but slowly moving and degrading the result of the automatic calibration.

Therefore, we provide an option to manually start the gyroscope bias calibration. In this mode, the user has to ensure that the sensor is at rest for 6 seconds after the calibration has been triggered. Furthermore, the automatic bias calibration needs to be disabled so the manual calibration is not accidentally overwritten.

C++ example code:

// disable automatic calibration
imu.setBoolProperty(ZenImuProperty_GyrUseAutoCalibration, false);
std::cout << "Starting gyroscope calibration, don't move sensor" << std::endl;
// start manual calibration
imu.executeProperty(ZenImuProperty_CalibrateGyro);
std::this_thread::sleep_for(std::chrono::seconds(6));
std::cout << "Gyroscope calibration completed" << std::endl;

Python example code:

# disable automatic calibration
imu.set_bool_property(openzen.ZenImuProperty.GyrUseAutoCalibration, False)
print("Starting gyroscope calibration, don't move sensor")
# start manual calibration
imu.execute_property(openzen.ZenImuProperty.CalibrateGyro)
time.sleep(6)
print("Gyroscope calibration completed")