CXP2.0的相机是否可以使用CXP1.1的Grabber
可以
答案是肯定的。
目前CXP共有2个发布版本：
2011年发布CXP1.1
2021年发布CXP2.1，向后兼容，新标准增加了同步功能、数据率放大了一倍。
只要是符合CXP标准、接插件匹配，那么CXP2.1是向前兼容CXP1.1的；
借用别人的总结，详细说明参考 https://www.qualitymag.com/articles/95138-what-should-i-know-about-coaxpress-20? ：
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- All cameras and frame grabbers will start up in CXP1.1, only switching to CXP2.0 when both the frame grabber and the camera support CXP2.0.
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- The CXP2.0 can reach up to 12.5 Gbit/s. This 12.5 Gbit/s mode is referred to as CXP12.
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- The CXP2.0 standard will support the new micro BNC connector.
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- CXP2.0 supports configurations where one camera is used with multiple frame grabbers in multiple computers such that the calculations can be performed in parallel.
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- GenICam features such as heartbeat (allows synchronization between cameras), events and timestamps (actively pushed from the camera to the frame grabber) will now be supported by CXP2.0.
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- CXP2.0 will allow a higher upstream data rate when operating at CXP10 and CXP12.
1. CoaXPress 2.0 is compatible with CoaXPress 1.1
All cameras and frame grabbers will start up in CXP1.1, only switching to CXP2.0 when both the frame grabber and the camera support CXP2.0.
This means that a CXP1.1 camera works on both the CXP1.1 and CXP2.0 frame grabber. This also means that a CXP2.0 camera works on a CXP1.1 frame grabber, although you will not be able to benefit from the advantages CXP2.0 has to offer.
2. Doubling of the maximum speed
The most obvious improvement is the increased data rate. As previously mentioned the CXP2.0 can reach up to 12.5 Gbit/s. This 12.5 Gbit/s mode is referred to as CXP12. Due to overhead the actual effective bandwidth is approximately 9.6 Gbit/s.
Just to give an example of what would become possible, let’s consider a sensor resolution of 5120x5120 and a bit depth of 10 bit. With four CXP2.0 channels at CXP12 the theoretically possible frame rate could be about 146 FPS. CXP1.1 with 4 channels at CXP6 would only achieve up to 73 FPS in this case.
One thing that needs attention from a system engineer’s point of view would be that while for CXP1.1 PCIe gen2 x8 or gen3 x4 is sufficient for most cases, for CXP2.0 PCIe gen3 x8 will become a minimum common requirement.
3. New connector type
The CXP2.0 standard will support the new micro BNC connector. CoaXPress started with the normal BNC connector, being a big connector, than the smaller DIN 1.0/2.3 connector became more commonly used. Unfortunately the DIN 1.0/2.3 connector resulted in some complaints from the market and it does not support the CXP12 high frequency signals.
Switching to the micro BNC connector does solve these issues. The micro BNC is in size comparable to the DIN connector, while retaining the robustness of the normal BNC connector. The micro BNC supports the required high frequency signals for CXP12 and even can achieve a smaller pitch if needed when placed next to each other. Furthermore the micro BNC connector is a well-established industry standard in the broadcast industry. Although being slightly more expensive compared to the DIN connector, it will give you a very reliable connector being able to do CXP12 speeds.
4. Stream to multiple hosts
Sometimes the computer is the limiting factor in processing speed. This can be the case if a lot of calculations have to be performed on the images. For these situations CXP2.0 supports configurations where one camera is used with multiple frame grabbers in multiple computers such that the calculations can be performed in parallel. This is an optional part of the standard, so ask the camera/frame grabber manufacturer which configurations they support.
The main supported configurations are:
Duplicate one image to multiple frame grabbers/PCs
Example: camera has four CXP connectors; each connector is connected to a different frame grabber in a different PC. One image is recorded by the camera and the complete image is sent to all four PCs.
Divide one image in parts and send to multiple frame grabbers/PCs
Example: camera has four CXP channels, each channel is connected to a different frame grabber in a different PC. The image can be divided in four horizontal or vertical stripes such that each stripe can be sent to a single PC for further processing.
5. Heartbeat, events and timestamps
Missing from CXP1.1, but being part of GenICam for many years is the heartbeat, events and timestamp. These GenICam features will now be supported by CXP2.0.
Heartbeat
The heartbeat allows for synchronization between cameras. Each camera has its own clock and timing. With the heartbeat message, the frame grabber can compute the exact actual time of the camera and link this to its own time clock. Often, the frame grabber clock can be synchronized with the Precision Time Protocol (PTP) IEEE 1588. When multiple cameras are connected to the frame grabber, the frame grabber can use the heartbeat to calculate the relative timing between the cameras and when synchronized with the PTP IEEE 1588, timing between cameras connected to different frame grabbers can be calculated as well. The heartbeat is required to allow for determining the exact moment an event occurred with respect to an event in another camera.
Events and timestamps
Events allow the camera to inform the frame grabber about the occurrence of certain events at a certain time. The time the event occurred is indicated by a timestamp as made possible by the heartbeat. Example events are start or end of exposure or reaching a too high temperature. Events are actively pushed from the camera to the frame grabber. No requests have to be sent to the camera (no polling is required) to monitor for the occurrence of events.
6. Faster Trigger
CXP2.0 will allow for a higher upstream data rate when operating at CXP10 and CXP12. CXP6 and lower use the CXP1.1 upstream data rate. This higher upstream data rate directly reduces the minimum trigger latency by half compared to CXP1.1. From a latency of 3.4 µs it goes to a latency of 1.7µs.
Here the latency is defined as the delay between the moment a trigger is being send and the actual moment the camera has received the trigger and can start the exposure.
