How to Use I2c Hub

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Overview

ROM-5780 supports one I2C hub.The I2C7 of ROM 5780 is converted to a 4-way I2C9 to I2C12 via TPA9545. It’s a quad bidirectional switch controlled via the I2C bus, the SCL/SDA upstream pair fans out to four downstream pairs, or channels. It should be noted that the devices connected on the I2C hub cannot be 0x73, because the address of i2c hub TPA9545 is already 0x73. If the address is the same, there will be a conflict and the data cannot be transferred.

Lists the bus of the I2C Hub

I2c-9 to I2c-12 is routed from the i2c7 of ROM-5780 through the hub. 

root@linaro-alip:~# i2cdetect -l
i2c-7   i2c             rk3x-i2c                                I2C adapter
i2c-9   i2c             i2c-7-mux (chan_id 0)                   I2C adapter
i2c-10  i2c             i2c-7-mux (chan_id 1)                   I2C adapter
i2c-11  i2c             i2c-7-mux (chan_id 2)                   I2C adapter
i2c-12  i2c             i2c-7-mux (chan_id 3)                   I2C adapter

Detect device address

For example I2C9 

root@linaro-alip:~# i2cdetect -y 9

Note: The device address connected on the hub cannot be 0x73.

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