GMSL Camera is a camera that uses GMSL (Gigabit Multimedia Serial Link) interface technology. Its core is to use specific physical and logical interfaces to achieve long-distance, high-reliability video and data transmission. At the physical level, the most notable external interface of GMSL Camera is the dedicated connector for connecting cables. These connectors vary according to the application scenario: in the automotive field, standardized FAKRA or more advanced HSD (High-Speed Data) coaxial connectors are commonly used; in the industrial or robotic fields, more robust M12 or other types of coaxial/shielded twisted pair connectors may be used. Through these connectors, GMSL Camera only needs a single coaxial cable (Coaxial Cable) or a pair of shielded twisted pairs (Shielded Twisted Pair, STP) to complete all key connections. This cable carries the high-speed serial GMSL signal, which is the physical carrier of the entire data transmission.
GMSL technology cleverly multiplexes (bundles) multiple key interfaces and functions within this single cable:
- High-speed video data downlink: This is the main function, converting the native high-bandwidth video data generated by the camera image sensor (usually the source of the parallel MIPI CSI-2 interface) into high-speed GMSL serial signals for transmission through the serializer chip inside the camera.
- Bidirectional control channel: A bidirectional low-speed control signal channel is also integrated in the same cable. This usually simulates or transmits standard I2C and/or SPI protocols, and sometimes also includes GPIO signals. The host processor (such as an on-board ECU or Jetson motherboard) sends control commands to the camera (such as adjusting exposure, gain, white balance, trigger mode, power on and off, etc.) and reads status information or register values through these channels, without the need for additional control cables.
- Power transmission (PoC - Power over Coax): Many GMSL Cameras support PoC technology. This means that the DC power supply (usually 9V-15V or 5V, depending on the design) that powers the camera module is also transmitted through the center conductor and shield of the same coaxial cable, completely eliminating the need for a separate power line. This is a key factor in simplifying wiring.
Inside the camera, its core interfaces include:
- Image sensor interface: The image sensor (from Sony, Onsemi, Omnivision, etc.) usually outputs raw video data to the GMSL serializer chip through a parallel MIPI CSI-2 D-PHY or CPHY interface. This is the logical source of the GMSL Camera video stream.
- Serializer chip interface: This chip receives MIPI CSI-2 signals from the sensor, as well as I2C/SPI control signals from the camera's onboard controller (if any) or directly transparently transmitted from the host. Its core role is to convert (parallel-to-serial conversion) parallel video, control signals, and possible clocks into high-speed GMSL serial signal streams and send them out through the coaxial cable. It also manages the power input of PoC.
On the receiving end (host system), the interface is also critical:
- Deserializer chip interface: Receives GMSL serial signals from the coaxial cable. The chip performs serial-to-parallel conversion to restore the high-speed serial stream to:
Standard MIPI CSI-2 signals: Output to the MIPI CSI-2 receive port of the host processor (such as NVIDIA Jetson, Qualcomm Snapdragon, TI TDA4). For the host processor, the input interface it sees is standard MIPI CSI-2, as if the camera is directly connected and the GMSL transport layer is transparent to it.
Restored I2C/SPI/GPIO signals: Output to the corresponding GPIO of the host processor or accessed through the I2C/SPI controller for controlling the camera.
- Host processor interface: The host processor obtains the video data stream through its native MIPI CSI-2 receive port and controls the camera through its I2C/SPI master controller and GPIO. The deserializer chip is usually configured by the host through SPI or I2C.
To summarize its interface architecture: The core of GMSL Camera is to use a single coaxial/twisted pair cable (physical interface) to transmit high-speed serial GMSL signals (physical layer protocol), which logically integrates the video stream from the camera's internal MIPI CSI-2 and the I2C/SPI/GPIO control channel for bidirectional communication, and often combines PoC power transmission. At the interface conversion point, the serializer on the camera side converts the parallel MIPI CSI-2 and control signals into GMSL serial signals; the deserializer on the host side restores the GMSL signals to standard MIPI CSI-2 and control signals, seamlessly connecting to the native interface of the host processor. This design makes GMSL Camera an ideal choice for applications that require long distance (10-15 meters+), high reliability, and simplified wiring (single cable integrates video, control, and power), and is widely used in automotive ADAS/autonomous driving cameras, robotic vision systems, and industrial vision inspection.
