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iPhone touch circuit repairing

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This video mainly explains the working principle of the iPhone 11Pro, 11Promax touch circuit

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The first step, when we buckle the battery,

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and the main power supply will provide the working voltage for the touch 5.1V conversion chip

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Step 2, when the power is turned on,

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the main power supply will output 1.8V power supply to provide working voltage for the touch screen

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Step 3, after we trigger the switch, the CPU is in normal working condition,

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it will read the data in the screen storage chip on the touch cable through the I2C bus

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to identify whether the screen is an original one

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Step 4, when the touch circuit is started,

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the main power supply sends a 32KHz clock signal to the touch screen

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Step 5, when the touch circuit is started, the CPU sends a reset signal to the touch screen

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Step 6, when the touch screen has the 1.8V power supply, the clock signal and the reset signal,

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the CPU will detect the touch screen through the SPI bus

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Step 7, after the touch screen detection is passed, some circuits will work first

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The touch screen will send a 5.1V turn-on signal to the conversion tubes U5500 and U5501

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Step 8, after U5500 receives the turn-on signal,

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it first boosts the voltage to generate 5.5V power supply, which is supplied to U5501

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After the U5501 has a 5.5V power supply and a turn-on signal,

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it will convert it to a 5.1V power supply to provide a working voltage for the touch screen

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Step 9, after the touch screen has 1.8V power supply, 5.1V power supply,

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clock and reset signals,

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the touch screen can work normally

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At this time, an interrupt signal will be issued to notify the CPU

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Step 10, after the CPU receives the interrupt signal,

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it will send touch data to the touch screen through the SPI bus,

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and then the touch screen can work normally

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These signals are the main working signals of the touch screen

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The touch screen also has some other detection signals

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The MANY_SCAN signal is the data synchronization signal sent from the touch screen to the main power supply,

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baseband power supply, CPU and other chips

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TOUCH_CTS is the touch data clearing signal

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After the touch screen work is completed, invalid data will be cleared and the CPU will be notified

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DISPLAY_BSYNC_TOUCH

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This signal is the display and touch synchronization signal sent by the CPU to the touch screen

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The UART bus is the data bus sent from the CPU to the touch screen

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This bus is mainly used to transmit data of other functional signals, such as 3D touch data

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When troubleshooting no touch faults, we must first measure all the main working conditions of the touch

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If the main working conditions are normal and there is still no touch,

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then measure other detection signals

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In the entire block diagram of the touch working principle,

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if one signal is abnormal, it will cause no touch failure

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Ok, that's all for this video