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This lesson is about the analysis when the I2C bus on the touch connector is short-circuited

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Take Xiaomi 10 Pro as an example

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Find its I2C bus, TS_I2C_SCL and TS_I2C_SDA

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These two lines are the I2C buses for touch

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They go to the connector J6400

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Switch to bitmap

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Right-click and click find the bitmap signal,

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so that you can find the touch connector and the line to which the touch connector leads

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The bitmap is in one-to-one correspondence with the real object

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When the I2C bus of the touch connector is short-circuited, how to repair it

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First look at its circuit

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Click pin 10, you can see that the pin goes to a resistor R3216,

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and also goes to the H36 pin of the CPU

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The clock of the I2C bus goes to the resistor R3217, also goes to the pin J36 of the CPU,

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and also leads to the pin 12 of the connector

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These two lines are exactly the same, but the pins of the chips they go to are different

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We will use one of them to analyze

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When measuring a short circuit on the touch I2C bus,

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first consider which components are on the line

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The components on the circuit include connector J6400, resistor R3212, CPU

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Since the resistor is a pull-up resistor, above 1,000 ohms,

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the short circuit has nothing to do with it

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It has nothing to do with the connector, unless the pin of the I2C signal is close to the ground wire,

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the connector has been touched and the pin is connected to tin, then the connector is considered

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Then all we have to consider is the CPU

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When we detect that the I2C bus is short-circuited, only the CPU is considered

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How to repair it at this time?

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Remove the CPU and re-solder it, measure the diode value,

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if there is no short circuit, the fault is repaired

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But the CPU is very difficult to have this kind of failure

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If you measure again after re-soldering, there is still a short circuit,

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which is basically irreparable, because the CPU itself is damaged

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That's all for this lesson