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iPhone touch circuit repairing
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This video mainly explains how to find the signals and measurement points
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of the touch chip of the iPhone 12 Promax
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Search method step 1, find the position number of the touch connector in the component map
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Step 2, search for the position number in the schematic diagram
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Step 3, find the corresponding signals in the circuit diagram
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Step 4, jump to the bitmap according to the pins, and view the connected components
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We can measure the voltage and diode value at the yellow points in the bitmap
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When checking the diagrams, first open the iPhone 12 Promax component map,
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schematic diagram, and bitmap
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Find the touch connector in the component map
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Search for the position number of the touch connector in the schematic diagram
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After finding the touch connector, find the corresponding signals
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Let's first find out the 1.8V and 1.2V power supplies of the touch chip
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The pins marked 1V8 are the 1.8V power supplies of the touch chip
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In the schematic diagram, we can see that many pins are marked with 1V8
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These power supplies are the 1.8V power supplies of the touch chip
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Jump to the bitmap according to the name,
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the 1.8V power supply is directly output by the main power supply
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There are many pins marked PP1V2_TOUCH in the schematic diagram,
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and these pins are the 1.2V power supplies of the touch chip
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Jump to the bitmap according to the name,
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the 1.2V power supply is directly connected to the main power supply
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Let's find the I2C bus from the CPU to the touch chip
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The I2C bus is the same as the I2C bus of the touch screen
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The B4 and A4 pins of the touch chip are the I2C buses
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Jump to the bitmap according to the name, the bus clock is directly connected to the CPU
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Jump to the bitmap according to the name,
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and the bus data is also directly connected to the CPU
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And the two I2C buses are connected to the display touch connector
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Let's find the 24MHz clock signal of the touch chip
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The F2 pin of the touch chip is a 24MHz clock signal
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Jump to the bitmap according to the name,
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the clock signal is connected to the CPU after passing through the fuse resistor R1660
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Let's find the reset signal of the touch chip
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The F5 pin of the touch chip is the reset signal
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Jump to the bitmap according to the name,
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the reset signal is directly connected to the CPU,
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and no other components are connected
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Let's find the SPI bus from the CPU to the touch chip
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The SPI bus has a total of 4 lines
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The E3 pin of the touch chip is the SPI bus chip selection pin
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Jump to the bitmap according to the name,
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and the chip selection signal is directly connected to the CPU
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The A3 pin is the SPI bus clock
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Jump to the bitmap according to the name,
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the clock signal is connected to the CPU after passing through the fuse resistor R1402
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The A2 pin of the touch chip is the data input of the SPI bus
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Jump to the bitmap according to the name,
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the data input is directly connected to the CPU
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The B2 pin of the touch chip is the data output pin
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Jump to the bitmap according to the name,
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the data output pin is also directly connected to the CPU,
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there is no fuse in the middle
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Let's find the power-on signal from the touch chip to the main power supply, LDO_EN
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The D3 pin of the touch chip is the turn-on signal
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Jump to the bitmap according to the name,
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and the turn-on signal is directly connected to the main power supply
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Let's find the 3.1V power supply of the touch chip
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The D2 pin of the touch chip is the 3.1V power supply
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Jump to the bitmap according to the name,
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the 3.1V power supply is directly connected to the main power supply
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Let's find the interrupt signal from the touch chip to the CPU
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The F4 pin of the touch chip is an interrupt signal
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Jump to the bitmap according to the name,
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and the interrupt signal is directly connected to the CPU
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Let's look for other detection signals
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MANY_SCAN is the forced synchronization signal sent by the touch screen
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to the touch chip and the main power supply
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The C1 pin of the touch chip is a forced synchronization signal
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Jump to the bitmap according to the name,
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the signal is sent by the touch screen to the touch chip, the main power supply and other chips
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Let's find the two synchronization signals sent by the display screen to the touch chip
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The E6 pin of the touch chip is the first synchronization signal
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Jump to the bitmap according to the name,
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the signal is directly connected to the display touch connector
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The D6 pin of the touch chip is the second touch synchronization signal
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Jump to the bitmap according to the name,
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the signal is directly connected to the touch chip from the touch screen
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Let's find the UART bus from the CPU to the touch chip
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The E7 pin of the touch chip is the UART bus emission
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Jump to the bitmap according to the name,
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and the emission signal is directly connected to the CPU
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The D7 pin of the touch chip is the UART bus receiving
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Jump to the bitmap according to the name,
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and the receiving signal is also directly connected to the CPU
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Let's find the SWD serial debug bus from the CPU to the touch chip
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The H6 pin of the touch chip is the debug bus clock
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Jump to the bitmap according to the name,
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the pin is connected to the CPU and the main power supply
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The F6 pin of the touch chip is the debug bus data
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Jump to the bitmap according to the name,
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the data pin is directly connected to the CPU, and no other components are connected
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In this way, we have searched all the signals in the block diagram of the touch chip
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In the schematic diagram, the other pins of the chip are the signals from the touch chip to the touch screen
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When we searched for the signal of the touch connector,
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we have already searched, so there is no need to search again
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Ok, that's it for this lesson
