Making a MIPI CSI 2 Camera Receiver #SBC #Standards #Video #FPGA
If you’ve ever worked with a Raspberry Pi, you’ve probably heard of the Raspberry Pi Camera Module. But what is the ribbon cable that comes out of it? The modules use interfaces created by the MIPI Alliance: Camera Serial Interface v2 and Camera Control Interface.
CSI uses low voltage differential signaling (LVDS) to transmit packets of data from the camera module to the receiver. There are a total of up to 5 LVDS pairs. The first is the clock. The clock frequency is configured via MIPI CCS. The four remaining pairs, referred to as lanes, transmit the data itself. More lanes means a higher possible framerate and larger resolutions since bandwidth can be doubled, tripled or even quadrupled. There are two types of packets: short and long. Long packets contain image data as a line of pixels in the image, or some other embedded data. Short packets usually contain control information (i.e. start/end of line, start/end of frame, etc.).
Technically, CSI is implemented on top of MIPI D-PHY, which defines the low-level physical and electrical characteristics of the interface. There should be a secondary low-power function on each lane including the clock that detects when a packet will begin and end.
The image above shows a block diagram of MIPI (from here). On one side there is application processor and other side is the peripheral. When peripheral is a camera, CSI applies (DSI for displays).
Though MIPI is closed specification, which means one has to be member of MIPI consortium to gain access to full specification. And membership of the consortium comes with a big price tag for individuals. Luckily, full specifications are already available just a right keyword web search away. DCS, CCS, DSI, CSI and DPHY are all specified and available with just few minutes of web search.
Interfaces are often made with FPGAs. There is a GitHub site which describes making a MIPI CSI 2 Receiver for Raspberry Pi. See the Blog Post here.
Adafruit publishes a wide range of writing and video content, including interviews and reporting on the maker market and the wider technology world. Our standards page is intended as a guide to best practices that Adafruit uses, as well as an outline of the ethical standards Adafruit aspires to. While Adafruit is not an independent journalistic institution, Adafruit strives to be a fair, informative, and positive voice within the community – check it out here: adafruit.com/editorialstandards
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.
Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7pm ET! To join, head over to YouTube and check out the show’s live chat – we’ll post the link there.