Block transfer with PCIe

Many embedded vision systems use image sensors that are directly integrated via the Camera Serial Interface CSI2. This often results in a functional limitation as well as a limitation in terms of image resolution and frame rate. PCI Express (PCIe) offers the possibility of implementing these solutions on a standard interface. With the camera family BVS CA-BN Balluff has a corresponding product in its portfolio that can be easily integrated and also enables higher image resolutions at corresponding frame rates.

As these cameras use the standardized PCIe interface, the cameras are integrated by installing the Impact Acquire SDK or copying the necessary runtime components. Installation packages are available for various platforms (ARM, ARM64, x86) and the Windows, Linux and MacOS operating systems. This does not require any changes to the operating system or the configuration of the computing target. After installation, the PCIe cameras of the BVS CA-BN series series PCIe cameras work immediately and are also accessible as a device for 3rd party software via the GenICam Transport Layer (GenTL) interface. The cameras are accessed via the features of the Standard Feature Naming Convention (SFNC) and vendor-specific additions. This also makes it easy to switch from a GigE Vision or USB3 Vision camera.

Up to 6,000fps with block scan mode

As the cameras in the BVS CA-BN series are equipped with an on-board Image Signal Processing Pipeline (ISP), known pre-processing steps can be carried out on the camera regardless of the performance of the computing target. Familiar functions from traditional vision cameras, such as debayering, look-up table, gamma correction or the application of a color correction matrix (CCM) can therefore be used in the same way and are implemented on the cameras without latency. Thanks to the optimum image sensor connection, extreme frame rates of several 1,000fps can also be achieved.

Normally, high interrupt rates occur on the connected computing targets at these frame rates, which can generally no longer be processed correctly beyond a certain point. In order to still enable these acquisition rates, the use of block scan mode is recommended. Here, several images are combined in the camera to form a memory block and transmitted at a correspondingly lower absolute overall frame rate. If ten images are combined, the frame rate is reduced by a factor of ten, resulting in a correspondingly lower interrupt load. One application that can use this method is the quasi-line scan camera. The image height in the ImageFormatControl is reduced to the minimum, resulting in a maximum frame rate due to the fast sensor connection. For example, a BVS CA-BN2-0032ZG with the 3.2MP Sony IMX252 image sensor (2,064x1,544 pixels) achieves a frame rate of over 6,000fps. Modern image sensors also offer additional special modes. Some of these are already available via camera features or can be implemented at the customer's request. For example, dual ADC, multiple ROI and fast trigger are already part of the current camera firmware.

Conclusion

PCI Express cameras make it possible to implement sophisticated applications in the embedded sector and behave identically to standard industrial cameras with GigE Vision or USB Vision interface in terms of software integration and handling. The biggest difference, however, is that the image reaches the receive buffer of the computing target directly at the readout rate of the image sensor via Direct Memory Access (DMA) and therefore does not burden the CPU of the host system.

The PCIe cameras BVS CA-BN2-0032ZG achieves a frame rate of over 6,000fps thanks to the block scan mode with the 3.2MP Sony IMX252 image sensor (2,064x1,544 pixels).