1.What is MIPI
- MIPI is an alliance formed by ARM, Nokia, St, IT and other companies. It aims to standardize the internal interfaces of mobile phones such as storage interface, display interface, RF/baseband interface, etc.
Reduce compatibility issues and simplify the design.
- Through different working groups, MIPI Alliance defines a series of interface standards, such as CSI, DSI, DIG RF and so on. Of The Ordinance
An interface standard can make the choice of chip and module more flexible and convenient.
- MIPI structure is divided into physical layer, protocol layer and application layer. MIPI applications have a CSI interface for the camera, a DSI interface for the display screen, and a Dig RF interface between baseband and RF.
2.What is the physical layer
- The physical layer includes M-PHY, C-PHY and D-PHY. D is the transfer speed of 500 Mbits/s, PHY is the physical layer, and C is the transfer speed of 500 Mbits/s
The transmission speed of M-finger is 1000 Mbits/s, and D-PHY is commonly used
- D-phy is a high-speed, low-power source synchronization physical layer, using a high-efficiency design
- D-phy uses 1 pair of source-synchronized differential clocks and 1 -4 pairs of differential data lines for data transmission. Data transmission using DDR mode, that is, there are numbers in the upper and lower edges of the clock
According to the transmission.
3.D-PHY defines two modes of transmission:
- Differential signal transmission, signal level in 100 mv ~ 300 mv (200 mv Pendulum)
- The speed of signal transmission is 80MBPS ~ 1Gbps (v1.0) or 80Mbps ~ 1.5 Gbps (v1.1)
- The DDR clock is transmitted by source synchronization from the Master device to the Slave device.
Four. LSB first, MSB last transmission.
- High power consumption and high transmission rate.
b.Low Power (LP) :
- Single-ended signal transmission, signal level in 0 ~ 1.2 V (1.2 V voltage swing)
- The signal speed is 10 Mbps
- LSB first, MSB last transmission.
- Low power consumption and low transmission rate.
- HS Mode is used only for high-speed data transfers, while LP Mode includes both Control Mode, low-power Data Transfer Mode (LPDT) , and
Ultra low power mode (ULPS)
2.MIPI Protocol Layer Csi-2
- CSI-2 protocol uses D-PHY physical layer protocol, also can use C-PHY physical layer protocol. CSI-3 can only use M-PHY as the physical layer.
- The CSI-2 Protocol mainly defines Lane Management Layer, Low Level Protocol, and Pixel to Byte and Byte to Pixel.
- In LP mode, the differential clock signal is still active, called a persistent clock, and vice versa is a non-persistent clock behavior
- Lane also opens the agricultural card as the initial SOT and starts sending the first byte, but the end time of each Lane may differ by one byte in the transfer time
- The general form of Low Level Protocol packets for CSI-2’s Data Lane is:
- There are two types of CSI-2 packets: long and short. Both long and short packages Start with SOT (Start of Transmission) and end with SOT (Start of Transmission)
EOT (End of Transmission) . Long packets of SOT are followed by Baotou (PH) and EOT by Packet headers
Basic structure of the long packet:
1.The first part is PH, packet header:
- It consists of Data ID, 16 bit WC, and ECC, with corresponding functions as shown above
- The ECC uses the Hamming Code approach, which corrects one-bit errors in PH (Baotou) or detects two-bit errors
2.The second part is the valid data for the package
3.The third part is PF, the checksum of the graph above;
- Checksum uses CCITT’s 16-bit CRC check, which is x ^ 16 + x ^ 12 + x ^ 5 + x ^ 0.
- CRC can only detect one or more errors in data transmission, but it can not correct the errors.
Four. WC, PACKET DATA, and CHECKSUM, are LSB first and MSB last, for a specific
In terms of bytes, it also sends low bits first, and then sends high bits.
Basic structure of a short packet
- The short packet uses the original WC location of the long packet as the packet’s data field, and the short packet sends up to two bytes of data at a time.
- Send LSB first, then MSB.
- Short packets are generally used to send synchronous control signals, it is not recommended to use short packets to send user data.
The CSI-2 protocol supports three common data formats: YUV (or YCbCr) , RGB, and RAW (or Bayer)
- YUV supports Lagacy yuv4208bit, yuv4208bit, yuv42010bit, yuv4228bit, and yuv42210bit.
- The RGB format supports RGB888, RGB666, RGB565, RGB555, RGB444, etc.
- The RAW format supports Raw6, RAW7, RAW8, Raw10, Raw12, and Raw14
MIPI protocol layer DBI
DBI has four display mode architectures