A fun.
As a chicken frozen engineer, bah, wrong type, is the driver engineer, the most basic hardware basic knowledge you have to understand it.
Here’s an example.
1. If you want to light up the Camera, you need to know which interface you are using, MIPI or Parallel?
2. What are the methods of data transmission?
3. What is the imaging principle of Camera?
, etc.
A little digression
1. As a white guy, why should I write a feature?
I want to,
One is to record their own growth process, record the data read, do what to think.
The second is to motivate yourself to keep moving forward. Just keep moving!
If one day I have the misfortune to become a Camera expert, then these are my self-taught growth process, which may be of some help to future generations.
If I have always been a salt fish, then this feature is a testament to my efforts and failure.
If you can’t fly, then run; If you can’t run, then walk; If you can’t walk, then crawl, but whatever you do, you have to keep moving forward.
I don’t know if I can have a career after 30 years old, if I still lost!
In a word, no matter what, we have to move forward every day, even if the steps are small, but at least I move forward!
Without further ado, this article knowledge points
Ii. Knowledge points
1.Camera imaging principle
The optical image generated by the LENS is projected onto the surface of the image Sensor, and then converted into an analog electrical signal, which is transformed into A digital image signal after A/D (analog-to-digital conversion) conversion, and then sent to the digital signal processing chip (DSP) for processing, and then transmitted to the CPU for processing through the IO interface. You can see the image through the LCD
An image SENSOR is a semiconductor chip whose surface contains hundreds of thousands to millions of photodiodes. When light strikes a photodiode, it generates an electric charge.
Currently, there are two SENSOR types:
1. Charge Couple Device (CCD), which is a relatively mature imaging Device in the current high pixel sensor, is a current signal of an action unit.
Complementary Metal Oxide Semiconductor (CMOS) CMOS signals are charge signals in points, which are more sensitive, faster and more power-efficient
ISP performance is the key to image smoothness, and JPEG Encoder performance is also one of the key indicators. The JPEG encoder is divided into hardware JPEG compression mode, and software RGB compression mode.
The function of DSP control chip is to transmit the data obtained by the photosensitive chip to Baseband and refresh the photosensitive chip in time and fast. Therefore, the quality of the control chip directly determines the picture quality (such as color saturation, clarity) and smoothness.
2.Image Sensor type (Camera data format)
A) YUV Sensor (low-end product)
The Data output from YUV Sensor is in YUV format, and the image effect is processed using the ISP inside the Sensor. After receiving the Data in YUV format, the BB terminal only converts the format, and does not process the effect. Due to the limited ISP processing capacity of the Sensor, In addition, YUV Sensor has a large amount of data (YUV422 format: 1 pixel and 2 bytes), and the Size is generally small. Common YUV sensors are below 5M
B) Raw Sensor (slightly better goods, obvious advantages)
Raw Sensor output Data format is Raw, the effect processing of the image uses THE BB terminal ISP, the BB terminal receives Raw Data for a series of image processing (OB, Shading, AWB, Gamma, EE, ANR, etc.), the effect is controlled by the BB terminal. Effects need to be debugged for different modules. Raw Sensor is currently the mainstream, and the amount of data is smaller than YUV sensor (1 pixel and 10 bits for RAW10 sensor), which is processed by ISP of the platform and can support a larger size
3. Hardware interfaces
In brief, the interface of Camera is divided into parallel and serial mode, while the main serial mode supported by MTK platform is MIPI interface.
The figure below describes the Parallel interface and MIPI interface
Although the hardware interface has Parallel interface and MIPI interface, in fact miPI is the mainstream, basically no Parallel figure! Later we will explain the hardware schematic of MIPI interface in detail!
4. Common basic concepts
The BB end of the CPU is baseband
A) Three-way voltage
The three voltages included in camera are analog voltage (VCAMA), digital voltage (VCAMD) and IO port voltage (VCAMIO).
B) the I2C signals
BB communicates with Sensor end through I2C (reading and writing registers), including SCL (I2C Clock) AND SDA (I2C Data) signals
C) Mipi several lanes
Mipi data is a pair of differential signals, MIPI_RDN and MIPI_RDP. If there are several pairs of such pins, it means that there are several lanes. The output signals of the same sensor may be 2 lane or 4lane due to different register setting
D) parallel
The general Data of the Parallel interface has 10 pins, respectively called Data0~Data9. When the Data signal output from the Parallel sensor is 8 pins, the eight pins are connected to Data0~Data7 or Data2~Data9. The configuration needs to be correct. It’s called connecting the upper eight or the lower eight, and a wrong connection can result in the following phenomena
e) Data Format
f) MCLK
External clock supplied to the Sensor by BB
g) PCLK
The clock output by the Sensor of the Parallel interface changes once and data updates once
H) mipi signal
Mipi signal includes MIPI Clock and MIPI Data, which is a high-speed signal used to transmit MIPI packets
5. Schematic diagram of hardware circuit
(Take TIMOVI_S9016 as an example.)
Schematic diagram analysis (pin function)
1. Power supply
The three voltages included in camera are analog voltage (VCAMA), digital voltage (VCAMD) and IO port voltage (VCAMIO).
A) VCAMD is DVDD digital power supply, which mainly supplies power to ISP
B) VCAM_IO is VDDIO digital IO power supply mainly supplies power to I2C;
C) VCAMA is AVDD analog power supply, mainly supplying power to the sensitive area and ADC part;
D) VCAM_AF is the power supply for the Camera auto focusing motor
2. The Sensor Input section
A) Rest foot: used for reset and initialization
B) PDN pin: Camera working state control :1. Normol work 2. Standby
C) Mlck foot: that is, MasterClock foot, the external clock provided by BB to the Sensor
3. The I2C part
BB communicates with Sensor end through I2C (reading and writing registers), including SCL (I2C Clock) AND SDA (I2C Data) signals
4. The MIPI parts
Mipi signal includes MIPI Clock and MIPI Data, which is a high-speed signal used to transmit MIPI packets.
Mipi data is a pair of differential signals, MIPI_RDN and MIPI_RDP. If there are several pairs of such pins, it means that there are several lanes. The output signals of the same sensor may be 2 lane or 4lane due to different register setting.
1.MIPI_RDN0 and MIPI_RDP0: used for data transmission
2.MIPI_RDN1 and MIPI_RDP1: used for data transmission
So it’s 2lane
In addition
MIPI_RCN and MIPI_RCP: clock signals
The leakage in the figure
A VIO18_PMU is missing in the figure: used for hoisting.
The way ahead is so long without ending, yet high and low I’ll search with my will unbending.
The above is the basic knowledge of Camera hardware that I think I should master during the process of reading the information.
Reference documentation
1. MTK data
2.MTK platform camera(camera) debugging tutorial points