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We will talk about the startup operation process in this lesson

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Mainly from the following two aspects

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First, Mobile phone startup process

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Second, the block diagram of the boot process

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How does a mobile phone work?

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Let's take a look

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The first step

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When we connect the power cord with the DC power supply,

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or buckle the battery to the battery holder,

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the battery will output the main power supply through the charging chip,

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VPH_PWR

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Xiaomi and Opop generally use VPH_PWR to replace the main power supply

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Vivo is also sometimes represented by VPH_PWR

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Huawei's main power supply is represented by VBAT_SYS

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Some mobile phones use SYS to refer to the main power supply

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Then the main power supply supplies a voltage to the power-on signal on the power-on line

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Xiaomi and Huawei's are usually 1.8 V

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In Oppo mobile phones,

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the positive electrode of the battery can provide a voltage of about 4 V to the power-on signal line

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through a pull-up resistor of about 100K惟 or about 200K惟

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When there is voltage on the power-on signal line,

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we press the power-on button of the power-on signal

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The power-on signal changes in voltage from 1.8 V to 0 V

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This jump is detected by the main power supply

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Who does the power chip output power supply to?

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For CPU, temporary storage, hard disk

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They are several main hardwares for booting

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After they are powered,

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the power chip will turn on a buck-boost chip,

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it is called BUCK_BOOST

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This chip will convert the main power supply into an auxiliary power supply

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This auxiliary power supply is VDD_BUCK_BOOST on Huawei

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Xiaomi will use VREG_BOB to indicate

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These two mobile phones will have this auxiliary power supply,

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which can be seen in the code name in the drawing

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Next, the main power supply provides a power supply to the crystal oscillator,

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and the crystal oscillator generates a frequency of 26MHz or 38.4MHz to the power chip

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26MHz is used in MTK platform,

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38.4MHz is commonly used by Qualcomm and some other platforms

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Then, the main power supply outputs the clock signal to the CPU

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The main power supply sends a reset signal to the CPU

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After the CPU is reset, it can start working

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The CPU resets the font library

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After complete, the CPU reads the self-test data in the hard disk,

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and performs self-test on the CPU itself, temporary storage, and GPU

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If there is no problem after the self-test is completed,

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it will send a power supply maintenance signal to the main power supply chip,

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so that the main power supply chip can maintain a normal output of power supply

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Then, the CPU will turn on the display circuit and let the display circuit work

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The CPU sends display data to the display screen,

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and the display screen will display the brand LOGO

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The CPU reads the hard disk system program and loads the Android system

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Next, the CPU turns on the touch circuit,

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audio circuit, wifi circuit, and some other circuits to make them work

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Finally, the CPU starts the radio frequency part,

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which is the signal part of the call

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At this time, the baseband needs to read the SIM card information,

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the signal receiving channel starts to work,

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and the operator is selected according to the SIM card information

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The transmission channel starts to work,

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confirms the connection with the base station,

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and displays the signal strength of the mobile phone

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The whole process of turning on the phone is now complete

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Okay, that's it for this lesson