***Question***

> Which GPIO pins does the Pi Zero camera use?

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***Answer***

> Rpi camera uses GPIO 0, 1, and also I2C 0.

*Notes*

*I think GPIO pins 0, 1, and I2C 0 are for OS to use.  Users should not use them.*  

I did once extracted the I2C 0 physical wires out and tried to fiddle with I2C 0 bus signals, because I did not have enough I2C buses to use.  But that is risky.

I also read that Rpi3B+ can setup more than one I2C bus, using device tree overlays. I tried and found no tutorials worked.  Those who claimed it worked, including one popular "instructable", never specified the Rpi hardware and software used.  So I think those tutorials were not reliable or fake.

Now the good news is that Rpi4B has 5 I2C buses.  I tried and found them reliable.

So my suggestion to newbies is NOT to use the GPIO pins (0, 1) and I2C bus (0).

In the new Rpi4B, there are more I2C buses for you to play with.  

And there is also no reason to use hijack systems GPIO pins 0, and 1, because 
you can always use GPIO extenders such as MCP23017/MCP23S17 to get many more GPIO pins. 

MCP23017's GPIO pins can also do many fancy interrupt functions, much more powerful than Rpi GPIO interrupt pins.  You can also connect many MCP23017 modules and so you can easily get 64 or more GPIO pins.  One good thing with MCP23x17 is that you can use either I2C or SPI, or both!   

You can also use PWM controllers such as PCA9685.  PCA9685's 16 PWM GPIO pins again give you more flexibility than the few Rpi GPIO PWM pins.  The PWM pins can can actually be used as GPIO pins, if you set duty cycle to 100%.  Again you can also place many PCA9685 on one I2C bus, to get more than 64 PWM / GPIO pins to use.

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[![rpizw cam gpio i2c][1]][1]

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***References***

(1) [Using multiple I2c buses on Rpi4B][2]

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*End of Answer*


  [1]: https://i.sstatic.net/Oi4mq.jpg
  [2]: https://raspberrypi.stackexchange.com/questions/104122/adding-i2c-bus-with-dtoverlay-does-not-show-up-in-i2cdetect