Complete Technical Guide for Euresys Coaxlink CXP Capture Card

Euresys Coaxlink CXP-12 Acquisition Card

In the field of industrial machine vision, with the continuous increase in sensor resolution and frame rate, traditional Camera Link or GigE Vision interfaces have gradually become bottlenecks in system throughput. The CoaXpress (CXP) standard is becoming the preferred choice for high-end vision systems due to its advantages of transmitting data, control, triggering, and power (PoCXP) over a single coaxial cable, as well as link speeds of up to 12.5 Gbps. The Euresys Coaxlink series of acquisition cards is based on this standard, providing a rich product portfolio from single channel to eight channel, covering PCIe 2.0/3.0 buses, and integrating powerful I/O toolboxes, multi card synchronization, and onboard processing capabilities. This article systematically analyzes the technical points of the entire Coaxlink series from hardware architecture, signal processing, I/O configuration to actual selection, providing a practical selection and integration reference for visual engineers.

Overview of CoaXpress and Coaxlink Series

CoaXpress is an asymmetric high-speed serial communication protocol with a downlink (camera to capture card) rate of up to 12.5 Gbit/s (CXP-12) and an uplink (capture card to camera) rate of up to 20.83 or 41.6 Mbps, used for camera configuration and triggering. A single 75 Ω coaxial cable can support up to 100 meters (at CXP-3 speed) and supports PoCXP (Power over CoaXPress) for camera power supply, simplifying on-site wiring. The Euresys Coaxlink series collection cards are fully compatible with CXP 1.0/1.1/1.1.1/2.0 standards and offer the following main models:

Model Connection Number Maximum Bandwidth Bus Interface Heat Dissipation Method Special Features

Coaxlink Mono CXP-12 LH 1 1250 MB/s PCIe 3.0 x4 Passive Cooling Single Channel, Low Cost

Coaxlink Duo CXP-12 2 2500 MB/s PCIe 3.0 x4 Active Fan Dual Channel, Flexible Configuration

Coaxlink Quad CXP-12 4 5000 MB/s PCIe 3.0 x8 active fan with four channels, maximum speed

Coaxlink Quad CXP-12 JPEG 4 5000 MB/s PCIe 3.0 x8 Active Fan Onboard JPEG Compression, Dual Stream Output

Coaxlink Octo 8 5000 MB/s PCIe 3.0 x8 Active Fan Eight Channel CXP-6, Multi Camera

Coaxlink Quad G3 4 2500 MB/s PCIe 3.0 x4 active/passive optional CXP-6, supports multiple data streams

Coaxlink Quad G3 DF 4 2500 MB/s PCIe 3.0 x4 Active Fan Supports Data Forwarding

Coaxlink Quad CXP-3 4 1250 MB/s PCIe 2.0 x4 Active Fan Long Distance (>100 meters)

Coaxlink Quad 3D-LLE 4 2500 MB/s PCIe 2.0 x4 Active Fan Onboard Laser Line Extraction (3D Contour)

Among them, the CXP-12 model supports up to 12.5 Gbps per link, while the CXP-6 and CXP-3 correspond to 6.25 Gbps and 3.125 Gbps, respectively. All cards provide rich I/O interfaces (differential, TTL, isolated input/output) and powerful I/O toolboxes, supporting motion encoder access, trigger generation, and synchronous control.

Core hardware and bus performance

The core of the Coaxlink acquisition card is a high-performance FPGA (Xilinx Kintex Ultrascale or similar), responsible for CoaXpress physical layer protocol parsing, image data preprocessing (such as bit depth unpacking, Bayer decoding, LUT mapping), and DMA transfer. The onboard memory capacity ranges from 512 MB (Mono) to 2 GB (Quad/Ecto) for image caching and retransmission.

Bus bandwidth is the key bottleneck. For example, the Coaxlink Quad CXP-12 has a theoretical aggregate bandwidth of 5000 MB/s and requires PCIe 3.0 x8 (peak 7800 MB/s, effective 6700 MB/s) to fully utilize it. Duo and Mono use PCIe 3.0 x4 (effective 3350 MB/s), which is sufficient to meet their bandwidth requirements. If the x4 slot is inserted, the Quad CXP-12 will automatically slow down, so the motherboard slot specifications must be confirmed when selecting.

PoCXP power supply can provide 24V DC/17W power per channel, supporting camera automatic detection and overload/short circuit protection. It requires an external+12V power supply through the onboard 6-pin PEG power interface, which is boosted to 24V by the onboard DC/DC converter. The CXP-12 model uses Micro BNC (HD-BNC) connectors with a bayonet locking mechanism and good shock resistance; The CXP-6/3 model uses DIN 1.0/2.3 push-pull connectors.

Image acquisition and processing function

Coaxlink supports both planar and linear camera types, compatible with multiple pixel formats: Mono8/10/12/16, Bayer (RG/GR/GB/BG) 8~16, RGB/RGBA 8~16, YCbCr 4:2:2, and YUV. For 10/12/14 bit data, it can be unpacked into 16 bits and aligned with LSB or MSB.

The array camera control provides precise external hardware triggering (with adjustable delay and trigger frequency division), exposure control, and strobe output, supporting camera exposure/readout overlap to improve frame rate.

Line array camera control is Coaxlink's strength. It supports continuous web inspection and discrete object scanning. By using the Quadrature Decoder (QDC) tool in the I/O toolbox, A/B orthogonal encoder signals can be integrated to dynamically adjust the camera line rate based on motion speed, ensuring physical size consistency of pixels in the motion direction. The Rate Converter tool allows the encoder frequency to be converted at a ratio of 0.001 to 1000 times, enabling arbitrary pixel aspect ratios and easy correction to square pixels. In addition, Backward Motion Cancellation automatically pauses data collection when material retreat is detected, and resumes data collection from the disconnected location to ensure that there is no overlap or loss of images.

Onboard image preprocessing includes: input LUT (monochrome camera), Bayer CFA decoding (multiple interpolation algorithms), flat field correction, and JPEG compression (Quad CXP-12 JPEG model only). Especially for the JPEG model, it has four independent JPEG encoders built-in, processing up to 250 MPixel/s per channel, and outputting JPEG and RGB preview streams with a typical 20 line delay, greatly reducing the CPU load of the host and suitable for multi-channel ultra high definition recording and monitoring applications.

I/O Toolbox and Trigger Synchronization

Coaxlink is equipped with a wide range of I/O interfaces (10 or 20 depending on the model), including high-speed differential inputs (compatible with RS-422/485, supporting 5MHz orthogonal encoders), 5V TTL bidirectional, isolated current type inputs (up to 30V, 50kHz, 2500V isolated), and isolated contact outputs (30V/100mA). All inputs have programmable digital filtering (debounce) and polarity reversal.

I/O Toolbox is a programmable event generator composed of multiple processing tools cascaded together:

LIN (Line Input): detects events generated by input edges.

QDC (Quadrature Decoder): decodes A/B signals, provides position values and motion directions, and has built-in reverse compensation.

DIV (Diver): Every N input events generate an output event.

MDV (Multiplier/Divider): Every D events generate M output events.

DEL (Delay): Delay the event by a programmable time or the number of encoder beats.

UAS (User Actions Scheduler): Execute user-defined actions (set/reset output pins) at predetermined times or encoder positions.

Through these tools, users can build complex triggering logic without writing FPGA code, such as using encoders to trigger circuit acquisition, using frequency division to achieve fixed interval sampling, or outputting strobe signals after delay.

C2C Link (Card to Card Link) is the core of multi card synchronization. Through the onboard 6-pin connector, multiple acquisition cards can be cascaded to achieve precise synchronization of trigger signals and exposure initiation. Within the same PC, the synchronization delay is less than 10ns; when crossing PCs (through InterPC adapters and RJ45 Ethernet cables), the delay is less than 265ns under a total length of 40 meters with 3 PCs, and can be expanded up to 32 PCs and 1200 meters. The maximum synchronization frequency is 2.5MHz (short distance) or 200kHz (long distance), which is very suitable for large-scale multi camera systems (such as multi view 3D detection).

Software Ecology and Debugging Tools

Coaxlink provides cross platform drivers that support Windows 7/8.1/10, Linux (x86/x86_64/aarch64), and macOS. The API hierarchy includes the EGrabber class (C++/. NET) and the GenICam GenTL Producer library, which are fully compatible with GenApi, SFNC, and GenTL standards and can seamlessly integrate with third-party visual software such as HALCON, Common Vision Blox, LabVIEW, etc.

Memento event logging tool is a powerful tool for development and debugging. It can record all events from cameras, capture cards, drivers to applications (including timestamps, contextual data, I/O status) and present them in timing diagrams and logic analyzer views. Whether it's troubleshooting trigger jitter, data loss, or performance bottlenecks, Memento provides visibility comparable to hardware logic analyzers, greatly reducing debugging cycles.

Direct GPU transfer supports AMD DirectGMA and NVIDIA CUDA, directly writing image data to video memory, bypassing CPU memory copying, reducing latency and CPU usage, suitable for deep learning and real-time processing scenarios.

For high-end users, Coaxlink Quad/Otto supports CustomizaLogic - allowing users to use Xilinx Vivado development tools to upload custom FPGA code to the acquisition card, occupying up to 70%~91% of FPGA resources to achieve customized image preprocessing or specialized algorithms without the need for additional hardware.

Selection Guide and Typical Applications

When selecting, comprehensive consideration should be given to the number of cameras, single channel bandwidth, whether compression or 3D processing is required, PCIE slot type, and heat dissipation conditions.

Single camera low speed (<1.25GB/s): Coaxlink Mono CXP-12 LH (passive cooling) or Duo (can connect dual cameras) have high cost-effectiveness.

Four camera high speed (total bandwidth up to 5GB/s): Coaxlink Quad CXP-12 (requires x8 slots) is the preferred choice; If the camera only supports CXP-6 (6.25Gbps), then Quad G3 (PCIe 3.0 x4, effective 3.35GB/s) is sufficient.

Ultra long distance (>40 meters): Coaxlink Quad CXP-3 (CXP-3 speed, over 100 meters) is suitable for monitoring or large-scale scene detection.

Multi channel JPEG recording: Coaxlink Quad CXP-12 JPEG, with four independent compression channels, suitable for security and motion analysis.

3D laser contour: Coaxlink Quad 3D-LLE, FPGA real-time extraction of laser line position (maximum/peak/centroid algorithm), output 16 bit height map, zero CPU usage, up to 38000 contour/second.

Large scale synchronization (multi card or multi PC): Choose models with C2C Link to achieve precise synchronization of dozens of cameras through cascading.

Common applications include PCB AOI (Automatic Optical Inspection), flat panel display inspection, solar cell sorting, print quality inspection, traffic monitoring, robot guidance, etc. Coaxlink's high bandwidth and flexible triggering characteristics make it an ideal front-end for these fields.

System integration precautions

Power supply: It is necessary to connect the auxiliary power supply (6-pin PEG), otherwise PoCXP cannot supply power and its I/O output capability is limited.

Cable length: Maximum 40 meters at CXP-12 speed, if the distance is longer, reduce the speed to CXP-6 or CXP-3.

Cooling: The active fan model should ensure proper ventilation of the chassis, while the passive cooling (LH model) should provide sufficient airflow (150 LFM).

Multi card installation: Multiple cards within the same PC need to be connected through C2C Link ribbon cables (length ≤ 60cm), and across PCs, InterPC adapters and shielded twisted pair cables need to be used.

Software configuration: Use GenICam Browser to confirm the camera connection status, configure the trigger source and exposure parameters; Monitor key events using Memento to ensure accurate triggering timing.