CoaXPress Host To Device Trigger
The CoaXPress Host To Device Trigger is a functionality of the CoaXPress I/O Channel that allows the Host (frame grabber) to trigger the
Device (camera) through the CoaXPress Link.
The CoaXPress Host Interface implements one CoaXPress Host to Device trigger transmitter for each connected Device.
Host to Device Trigger Source
The CoaXPress Host to Device Trigger transmitter can be sourced from:
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The Camera Trigger output of the associated Camera and Illumination Controller |
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Any input-capable General Purpose I/O |
The trigger source is indirectly controlled through the CameraControlMethod GenApi feature.
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When CameraControlMethod is set to RG or RC, the trigger source is the Camera Trigger output of the
associated Camera and Illumination Controller. |
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When CameraControlMethod is set to EXTERNAL: |
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The trigger source is the line source of a dedicated LIN tool of the I/O Toolbox: LIN1 for Device0, LIN2 for Device1, ... LIN8 for
Device7. |
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Any input-capable GPIO line can be used as trigger source by configuring the LineInputToolSource of
the dedicated LIN tool. |
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The polarity of the external trigger signal can be controlled with the LineInverter setting of the selected I/O
Control block. |
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The time constant of the glitch-removal filter can be adjusted through the LineFilterStrength setting of the selected
I/O Control block. |
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When CameraControlMethod is set to INTERNAL: |
Applies to the following firmware variants of PC3603 Coaxlink Quad CXP-12, PC3603-4 Coaxlink Quad CXP-12 and PC3623 Coaxlink Quad CXP-12 Value:
(1-camera, line-scan), (2-camera, line-scan)
(1-camera, line-scan), (2-camera, line-scan)
any I/O Toolbox event can generate a CoaXPress LinkTrigger0 or LinkTrigger1 message. Therefore:
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Select theCoaXPress Host to Device trigger message source by setting the CxpTriggerMessageSelector feature of the Device module to LinkTrigger0 or LinkTrigger1 |
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Select the I/O Toolbox event by setting CxpTriggerMessageSource to the desired value |
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When CameraControlMethod is set to NC, the Host to Device Trigger transmitter is disabled. |
Host to Device Trigger Transmitter - Default Settings
The implementation of the CoaXPress Host to Device Trigger transmitter complies with the requirements of the CoaXPress
standard for a low-speed CoaXPress Host to Device Trigger when it is configured with the default settings:
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CxpTriggerMessageFormat = Pulse |
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CxpTriggerAckTimeout = 20.0 |
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CxpTriggerMaxResendCount = 3 |
The transmitter initiates a trigger transaction on both edges of the trigger source signal:
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It computes a delay value allowing the receiving device to recreate the event with a fixed latency. |
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It inserts a high-priority "trigger packet" on the low-speed host-to-device connection at the next character boundary. |
Then, the transmitter waits for the acknowledgment from the Device (camera):
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If the acknowledgment is received before the expiration of the timeout, the transaction terminates normally. |
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If no acknowledgment is received within the 20 µs timeout, the transmitter performs a retry: it resends the trigger packet and
initiates a new waiting period for the acknowledgment. |
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If no acknowledgment is received after 3 times, the transaction terminates abnormally. |
The transmitter doesn't initiate a new transaction while the previous one is not completed.
Trigger message transactions using default settings
Case 1 and case 2: the camera acknowledges each message as expected
Case 3: no acknowledgment from camera. Abort after 3 retries
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NOTE:
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In CoaXPress v1.x, LinkTrigger0 was called "Rising edge" and LinkTrigger1"Falling edge" |
Events Reporting
The transmitter reports the following events:
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CxpTriggerAck: Received acknowledgment for CoaXPress Host to Device trigger packet. |
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CxpTriggerResend: Resent CoaXPress Host to Device trigger packet. |
See also: Advanced Trigger Transmitter Settings and Camera Trigger Jitter Compensation
