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Getting Started with OpenZen
OpenZen allows to access many different sensor models which are connected via different transports layers with one unified programming interface. This allows to develop applications which support a wide range of sensors and allows to easily adapt your application to new or additional sensors.
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For this page, the example codes are written in C++. We also have Python, C and C# examples in our repo, please check the side navbar for more details (compilations and programming languages support).
IO Systems
To communicate with the sensor hardware, please specify through which IO systems OpenZen should access your sensor.
| Note |
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Permissions and settings required for Linux userCOM port: In the terminal execute Bluetooth: To be able to connect to any Bluetooth sensor, it first needs to be paired via the operating system’s device manager. |
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You can find the full list of available IO systems in the section io-systems.
Sensor Components
A sensor can have multiple components which supply various types of sensor data. Once the connection
to a sensor has been established, the available components can be queried. Sensor data and their properties can be access / modified.
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Provides global position measurements via GPS, BeiDou, GLONASS and Galileo, the associated error estimates and information on the quality and mode of the GNSS fix. Only IG1P sensor has GNSS component.
Keys for Sensor Data Access
Sensor data are collected as events in by the client program. Most of the keys listed in imuData and gnssData are available for access. Note that there are a few limitations on specific data fields:
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Field name (explanation) | IG1 / IG1P | U3 | NAV3 | U2 | B2 | BE / ME |
|---|---|---|---|---|---|---|
g1 low range | o 3 axes high-precision gyro | x | o vertical axis high-precision gyro | o | o | x |
g2 general-purpose high range | o | o | x | x | x | o |
| Info |
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To debug your OpenZen program, we have a Windows GUI client to work with sensors. There are 2 communications that our sensors follows. They are categorized as follows:
LPMSControl2 for LPMS3 sensors, OpenMAT for LPMS2 sensors. For detailed information of all our sensors, please visit our Knowledge Base. |
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| Note |
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Information above should have already given you a pretty nice illustration of the OpenZen library’s compositions. You can skip reading the following sections if you understand the sample program. The old OpenZen docs can be found at https://lpresearch.bitbucket.io/openzen/latest/getting_started.html |
Creating an OpenZen Client
The following description will use the C++ interface to OpenZen but other language bindings use the same concepts described here. To see the description how to use the other language bindings, please have a look at the respective section for the language you are interested in.
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auto clientPair = zen::make_client();
auto& clientError = clientPair.first;
auto& client = clientPair.second;
if (clientError)
// error when creating OpenZen client
return clientError; |
Receiving Events from OpenZen
Every ZenClient instance contains its own event queue which accumulates events from all sensors that were obtained on that client. Events can either be polled using ZenClient::pollNextEvent or waited for using ZenClient::waitForNextEvent.
The only way to terminate a client that is waiting for an event, is by destroying the client or preemptively calling ZenClient::close.
Listing Available Sensors
The IO systems available on your platform can automatically list all available sensors connected to the system. In order to do this, you need to call the method ZenClient::listSensorsAsync to start the query for available sensors. Depending on the IO systems, it can take a couple of seconds for the listing to be complete.
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| Code Block |
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bool listingComplete = false;
while (!listingComplete) {
const auto pair = client.waitForNextEvent();
const bool success = pair.first;
auto& event = pair.second;
if (!success)
break;
if (!event.component.handle)
{
switch (event.eventType)
{
case ZenEventType_SensorFound:
std::cout << "Found sensor " << event.data.sensorFound.name << std::endl;
break;
case ZenEventType_SensorListingProgress:
std::cout << "Sensor listing progress " << event.data.sensorListingProgress.progress
<< " %" << std::endl;
if (event.data.sensorListingProgress.complete) {
listingComplete = true;
}
break;
}
}
} |
Connecting to a Sensor
A sensor found by the ZenClient::listSensorsAsync call can be connected via the OpenZen client using the ZenSensorDesc which is contained in the event.data.sensorFound of the ZenSensorEvent_SensorFound. The method call to ZenClient::obtainSensor returns a std::pair where the first entry is a possible error code and the second entry is an instance of the object zen::ZenSensor which can be used to access the Sensor's
properties.
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You can connect multiple sensor via one ZenClient and the events of all sensor will be available on the event queue of the ZenClient instance.
Reading and Modifying Sensor Properties
OpenZen allows to read an modify the properties of connected sensors. Which properties are available depends on the concrete sensor connected. You can find more information on sensor properties in the section supported-sensors-label.
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auto sensorModelPair = sensor.getStringProperty(ZenSensorProperty_SensorModel);
auto & sensorModelError = sensorModelPair.first;
auto & sensorModelName = sensorModelPair.second;
if (sensorModelError) {
// error while reading the string property from the sensor
return sensorModelError;
}
std::cout << "Sensor Model: " << sensorModelName << std::endl; |
Accessing Sensor Components
To access a specific component of a sensor, the method call ZenSensor::getAnyComponentOfType can be used to retrieve the component of a specific type. If this component is not available on this sensor, an error will be returned.
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As with the ZenSensor class the ZenSensorComponent returned by ZenSensor::getAnyComponentOfType call can be used to access and modify the properties of the sensor component.
Reading Sensor Values
To start receiving data from a connected sensor, you need to ensure that the sensor is in streaming mode to send out data on its own:
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if (event.component.handle == g_gnssHandle)
{
switch (event.eventType)
{
case ZenEventType_GnssData:
std::cout << "> GPS Fix Type: \\t = " << event.data.gnssData.fixType << std::endl;
std::cout << "> Longitude: \\t = " << event.data.gnssData.longitude
<< " Latitude: \\t = " << event.data.gnssData.latitude << std::endl;
break;
}
} |
Closing the Sensor Connection
Once you are done with sampling sensor values, you can release the connection to the sensor and close the connection with the client:
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