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iPhone common buses
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In this video, we mainly explain the meaning, function,
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identification and failure phenomenon of I2C bus
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The I2C bus is a simple bidirectional two-wire synchronous serial bus developed by Philips
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Only two wires are needed to transfer data bidirectionally between chips
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The I2C bus consists of a data line SDA and a clock line SCL
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The bus interface is integrated inside the chip,
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and no special interface circuit is required outside
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In iPhones, it is mainly used to transmit data
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between CPU and chip or between CPU and peripherals
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In the iPhone bus block diagram,
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we can see that there are many I2C buses between the CPU to the chip and peripherals
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It is mainly used by the CPU to communicate with the chip
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Detection function of the I2C bus
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We are in maintenance, if the camera is damaged,
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we will replace the camera
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After the replacement,
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when viewing the inspection report with Aisi Assistant,
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it will prompt that the camera has been replaced
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After the iPhone is connected to the computer,
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open the Aisi Assistant to view the inspection report
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There are camera information in the factory value column
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and the readout value column
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If the information is inconsistent,
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the test result will prompt you that the camera may have been replaced
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Where did this prompt message come from?
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When the CPU is turned on,
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it reads the data stored in the camera through the I2C bus
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If the data does not match the factory data, it will prompt out
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There will be a prompt message when replacing the battery on iPhone xs and above,
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or when replacing the screen on iPhone 11 and above
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These messages are read and identified through the I2C bus.
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This kind of information that prompts an error is the
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information detected when I2C is working normally
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What happens if the I2C bus is short-circuited?
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When the I2C is seriously short-circuited,
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the iPhone will not be able to turn on, and there will be a stuck white apple
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The stuck white apple means that the screen will display the Apple logo screen after booting,
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but it will remain stuck for a long time
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There is also a white apple restart
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The white apple restart means that the Apple logo screen appears after the phone is turned on
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After waiting for about a minute, the phone will go black again,
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and then the Apple logo icon will appear
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For example, after the current iPhone is turned on,
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the Apple logo icon appears on the screen
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After a while, the screen will appear black,
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and then the white apple icon will appear.
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This fault belongs to the white apple restart
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There is another kind of fault is an unscheduled restart,
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that is, the iPhone shuts down with a black screen at an indefinite time,
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and then automatically turns on again
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This phenomenon may be caused by the I2C bus
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Next, let's go to the drawings to check the I2C bus
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Let's take the iPhone 8p Qualcomm mainboard as an example
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In the drawing, U1000 represents the CPU
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There are many groups of I2C buses inside the CPU
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Each group of buses has two lines, SCL and SDA
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These I2C buses are connected to different components
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What components are connected to the first set of buses?
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We can see from the query that it is issued by the CPU and connected to the main power supply
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Let's look at the I2C1 line
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The I2C1 bus is connected to the fuse resistor R4309,
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and then connected to the J4300 socket
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This socket is written on the I2C bus of the microphone 1,
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indicating that the microphone is also detected through the I2C bus
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There are some other I2C buses below,
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as you can see in the block diagram, they connect more components
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When there is a problem with the I2C bus,
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it will lead to the failures we mentioned just now
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Ok, this is the introduction of I2C bus
