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iPhone common buses

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In this video, we mainly explain the I2S bus

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I2S bus is a bus standard developed by Philips for

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audio data transmission between digital audio devices

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This bus is specially used to transmit the audio data of the integrated circuit,

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also known as the built-in audio bus

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I2S bus is commonly used in iPhone mainboards with 4 lines,

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and 12 series will have 5 lines in progress

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The line is mainly divided into three important signals

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The first signal serial clock SCLK, also called the bit clock BCLK,

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is the data corresponding to each bit of digital audio

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The second signal, frame clock LRCK, also known as WS,

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is mainly used to switch the data of the left and right channels

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And the third one is SDATA, has two lines,

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one is output OUT and the other is input IN

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Sometimes, in order to make the system time better synchronized,

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another clock signal is needed, It is MCLK, short for main clock,

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also called the system clock

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In the iPhone bus block diagram,

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we can see that there will be an I2S bus between the audio amplifier,

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main audio and baseband

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These lines are mainly used to transmit audio data in iPhones

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For example, when we make a call,

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the microphone first receives the data and sends it to the main audio

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The main audio sends the audio data to the CPU through the I2S bus

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After the CPU receives the data, it transfers the data to the baseband,

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and the baseband sends the voice signal through the

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power amplifier chip to the base station

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Problems with this bus will cause many failures,

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such as no sound when playing songs,

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no sound when answering calls

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This kind of failure is very common in models with double-layer mainboards above the iPhone x

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For example, iPhone 11,

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its baseband is in the lower layer and the CPU is in the upper layer

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Its voice signal is connected to the CPU through the mid-level connection point

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When the iPhone is dropped,

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the mid-level connection points will be in poor contact,

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and the signal will not be sent from the baseband to the CPU,

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so it will lead to the common call without a receiver or without a call

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Application of I2S bus in iPhone

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Let's take iPhone 11 as an example to find out the I2S bus of this model

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We first found the cpu in the drawing

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Among the internal modules of the CPU,

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there is a module specifically identified called I2S,

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which is the built-in audio bus of the iPhone

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It is divided into three groups of buses: I2S0, I2S1, and I2S2

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These three groups of buses transmit different voice data respectively

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I2S0 bus has 5 lines, I2S1 has 4 lines, I2S2 also has 4 lines

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I2S0 bus is mainly used to connect large audio

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The I2S2 bus is mainly used to connect the baseband

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If the bus connection point is soldered empty,

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it will lead to no handset and no transmission when making a call

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Ok, this is the introduction of I2S bus