Month: November 2020

The Institute of Embedded Systems at ZHAW developed a driver for the deserializer DS90UB954 and serializer DS90UB953 from Texas Instruments. The driver was tested on the RaspberryPi 4, NVIDIA Nano and NVIDIA Xavier modules.

FPD-Link III is a cost-effective solution for high speed video transmission. The video data, the bidirectional configuration signal and the power supply are all transmitted over a single coaxial cable. At the length of up to 15 m the coaxial cable can support data rates of 6 Gbps.

In order to use our FDP-Link III driver (link driver) on different hardware, the driver was designed to be highly configurable. Additionally, the driver can be used with various FPD-Link III cameras. Instead of integrating the FPD-Link III part into already existing camera sensor drivers, the link driver is standalone and creates a transparent CSI and I2C link to the data source. This means that after the driver has set up the FPD-Link III connection, the sensor driver can be used without modifications.

Transparent Link

The following figure shows an example of a sensor driver which controls a camera sensor directly over I2C and configures the video interface

Adding an FDP-Link III connection means that the I2C interface and the video channel will be routed through the coaxial cable. The deserializer and serializer are responsible for the conversion and forwarding of I2C and video data. The following figure shows the link driver configuring the deserializer and serializer over I2C. Once the setup is done, the sensor driver can configure the camera sensor over the I2C interface. Since the link is transparent, no changes have to be made to the sensor driver.

Configurability of the Driver

The following configurations can be done in the device tree:
– I2C address of deserializer/serializer
– Number of MIPI CSI lanes (the camera sensor and the hardware do not need to have the same number of lanes)
– MIPI CSI lane speed
– Enable/disable continuous clock
– Enable/disable test pattern of deserializer/serializer
– Virtual channel ID mapping
– Configure GPIOs of deserializer/serializer
– Set I2C alias addresses

Follow this link for the Driver source code and documentation A detailed description of device tree configurations can be found in ds90ub95.txt.

A hardware reference design for the Raspberry Pi can be found in our blog: Power over Coax FPD-Link III Link Streaming Adapter for Raspberry PI CSI-Interface

The Institute of Embedded Systems at ZHAW has developed an open source adapter which allows streaming of a CSI-2 Camera interface to a Raspberry Pi. This allows connecting cameras with CSI interface via a long distance cable (up to 15m) to the CSI-2 input of a Raspberry Pi.

The long range adapter uses FPD-Link III high-speed video transmission technology by utilizing the existing MIPI CSI-2 interfaces of cameras and Raspberry Pi. A deserializer converts the FPD-Link III signal to CSI, is based on the DS90UB954 from Texas Instruments (TI). The counterpart located at the Raspberry Pi camera is based on the serializer DS90UB953 from TI. With these two components it is possible to transmit high-speed video data over a single coaxial cable which can be up to 15 meters long. Another advantage of FPD-Link III is the power over coax (PoC) capability, which transmits the power required for the camera sensor directly from the Raspberry Pi.
The schematics and PCB designs are open source and available here.
A driver for the Texas Instruments DS90UB95x serializer and deserializer can be found in our blog Linux Driver for TI DS90UB95x FPD-Link III serializer and deserializer