Open source FPGA designs for the SDI to MIPI CSI-2 Bridge

The usual practice in FPGA development is to treat bitstreams as proprietary firmware, but through its work Antmicro is showing how a more software-centric and open source-driven methodology can offer more control and significant productivity gains to customers who rely on FPGAs in their use cases. Our work with open source FPGA tooling, cores and hardware, has brought this open source-based approach to every step of FPGA development and resulted in practical results in many high-value use cases.

To follow our practice and enable complete control for our customers, we are now releasing the open source FPGA designs for the SDI-MIPI CSI-2 Bridge which we released as open hardware some time ago and which has found its use in dozens of applications, both standalone and integrated into customized devices Antmicro helps build.

SDI to MIPI CSI-2 Bridge overview

The SDI to MIPI CSI-2 Bridge has already been described in detail in a separate blog note some time ago, however, since the initial release of the board we have introduced a number of improvements - the current hardware revision is 1.3.0. The device, based on the Lattice CrossLink FPGA, converts Serial Digital Interface (SDI) (up to) 1080p video into MIPI Camera Serial Interface 2 (CSI-2) and enables connecting SDI cameras and video accessories to edge AI platforms which often include the MIPI CSI-2 interface. The board features Antmicro’s standard 50-pin Flexible Flat Cable (FFC) output connector that is compatible with a range of our open hardware boards, e.g. Open Source Jetson Baseboard, Kria K26 Devboard, Snapdragon 845 Baseboard and the new Jetson Orin Baseboard.

The bridge is also electrically compatible with the recently updated Jetson AGX CSI Adapter, which can be used with the NVIDIA Jetson Orin Developer Kit.

The SDI to MIPI CSI-2 Bridge has been successfully applied in a variety of sectors, most notably robotics, autonomous vehicles, and filmmaking. The SDI-MIPI PCB can be manufactured and assembled from the design files provided on GitHub. Preassembled boards are also available for purchase from our partner Capable Robot Components.

Open source FPGA design for the SDI to MIPI CSI-2 Bridge

To make the setup entirely reproducible for customers, Antmicro has released the SDI to MIPI CSI-2 Bridge bitstream sources on GitHub. The project consists of two parts:

• a Timing GeneratorI IP block written in Migen to generate correct timings for the MIPI transmitter from synchronization signals acquired from the SDI deserializer,
• a Lattice CMOS2DPHY IP core for converting and transmitting parallelized data in the MIPI CSI-2 standard.

The FPGA design uses video data acquired from the Semtech GS2971A deserializer to generate correct MIPI timings. It converts hsync and vsync signals into Line Valid (lv) and Frame Valid (fv) that are passed down to the CMOS2DPHY IP core along with the pixel data which produces a CSI-2 video stream.

Due to the fact that the parameters of the CMOS2DPHY IP need to be hardcoded for each video format, the CrossLink FPGA requires loading different bitstreams to change video resolutions. This can be done without power cycling the system.

So far, we have provided sources for the bitstreams for three video formats, each available in a 2- and 4-lane configuration:

• 1080p60
• 1080p30
• 720p60

With the bitstream now released as open source, it becomes easier to customize to other resolutions, frame counts and formats which will be enabled over time. For detailed instructions on building the FPGA bitstream, refer to the project’s README.

With the current 1.3.0 hardware revision, uploading the bitstream can be done directly over the I²C interface. A description of how to set up a host system for the SDI-MIPI bridge on a Jetson Xavier NX module on Antmicro’s Jetson Nano Baseboard and how to program the bridge is provided in the project’s documentation.

Building custom FPGA solutions with Antmicro

The popularity and widespread use of the original SDI to MIPI CSI-2 Bridge across many different industries led to the development of a next generation open source SDI-MIPI converter, which is also available on Antmicro’s GitHub. Following up on the work described in this note, another project is in progress to build open source software and FPGA code for the new, more powerful board - so stay tuned for upcoming developments!

Antmicro offers FPGA expertise combined with vast experience with open hardware, tooling and cutting-edge video and audio processing devices. With our vendor-neutral and software-driven approach, we can assist you at every stage of the FPGA design process, providing flexible solutions for your custom needs. For more information about our open source FPGA and hardware projects reach out to us at contact@antmicro.com.