Multi-Camera Controller#

A Harp CameraController (Gen2) device is utilised together with a CameraController (Aeon.Video) node to configure and synchronously trigger two sets of cameras which can operate at different framerates.

Nodes#

CameraController#

The CameraController (Aeon.Video) node establishes a connection to the Harp CameraController (Gen2) device, which will generate two timestamped camera trigger event streams to synchronously trigger two sets of one or many cameras. This enables direct control to start and stop connected cameras, and configuration of the frequency of the camera triggers.

Properties#

General#

Property name	Description
PortName	The COM port the physical CameraController is connected to

Camera trigger configuration#

Property name	Description
GlobalTriggerFrequency	Set the frequency of the first (global) set of camera frame triggers
LocalTriggerFrequency	Set the frequency of the second (local) set of camera frame triggers

Subjects#

Events and commands from the device are collected, in some cases processed, and passed to published Subjects. Here you set the names used for these Subjects to identify these events, commands or data streams for this specific device. Each of these Subjects is published and becomes accessible in the Bonsai editor’s toolbox anywhere in the workflow using its name.

Device event subjects#

Subject name	Type	Description
VideoEvents	`Harp.HarpMessage`	A stream of all events emitted by the Harp CameraController (Gen2). Also directly output by the node

Other output subjects#

Subject name	Type	Description
GlobalTrigger	`Harp.CameraControllerGen2.CameraEvent`	A stream of timestamped camera trigger events generated at the `GlobalTriggerFrequency`
LocalTrigger	`Harp.CameraControllerGen2.CameraEvent`	A stream of timestamped camera trigger events generated at the `LocalTriggerFrequency`
GlobalTriggerFrequency	`double`	`BehaviorSubject` to store the value of `GlobalTriggerFrequency`
LocalTriggerFrequency	`double`	`BehaviorSubject` to store the value of `LocalTriggerFrequency`

Device command subjects#

Subject name	Type	Description
StartCameras	`object`	Any item sent to this `BehaviorSubject` immediately begins camera acquisition
StopCameras	`object`	Any item sent to this `BehaviorSubject` immediately stops camera acquisition

Usage#

Create a GroupWorkflow and give it an appropriate name, e.g. “VideoController”. Inside, place a CameraController (Aeon.Video) node, externalise all properties, and connect it to the WorkflowOutput.

Aeon.Acquisition.CameraController

GUI#

None

Logging#

All events can be logged using a LogHarpState (Aeon.Acquisition) node. The example below logs the state of all relevant Harp registers in a dedicated folder.

Aeon.Acquisition.LogHarpState

Logs can be identified by their register address, summarised here.

Data schema

Register name	Access	Address	Type	Mask Type	Description
TimestampSeconds	Event	8	U32	-	Heartbeat
Cam0Event	Event	32	U8	CameraEvents	Signals a frame was triggered on camera 0
Cam1Event	Event	33	U8	CameraEvents	Signals a frame was triggered on camera 1
ConfigureCam0Event	Write	34	U8	EventConfiguration	Configures the event on camera 0
ConfigureCam1Event	Write	35	U8	EventConfiguration	Configures the event on camera 1
StartAndStop	Write	36	U8	CameraFlags	Starts and stops the cameras immediately
TriggerFrequencyCam0	Write	45	U16	-	Specifies the trigger frequency for camera 0
TriggerFrequencyCam1	Write	52	U16	-	Specifies the trigger frequency for camera 1

For the full register and bitmask schema for the CameraControllerGen2 device, see the corresponding device.yml.

State persistence#

Not required for state recovery

Alerts#

In Aeon, the “VideoEvents” Subject is useful as a timer for environment monitoring workflows, such as regular notification of a summary of the current state of the experiment each hour. See Alerts for details on configuring these alerts.

As with other Harp devices in the system, this stream should be added to the HeartbeatSources to be monitored using the SynchronizerMonitor (Aeon.Acquisition) node to ensure continuous synchronisation with all other synchronised devices on the system.