Machine i2c deinit

[jaenrig-ifx]

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To be reviewed after #95.

Added deinitialization function to i2c module. This is directly added to the extmod.

Docs amendments will be done after the complete machine module is refactored for the pin_phy.

[github-actions]

Code size report:

   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +0 +0.000% PYBV10
     mimxrt:    +0 +0.000% TEENSY40
        rp2:    +0 +0.000% RPI_PICO
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS

[NikhitaR-IFX]

Not completely sure if this is needed. So far I understand, this is to point to our version of implementation of function, if there is already one implemented in other module (for ex. in extmod/i2c). And I think there is not deinit in extmod. But I might be wrong and feel free to correct.

[jaenrig-ifx]

Correct. That was not declared in the extmod. And I added it.
How can the i2c then be deinited? I wonder how other ports handle softreset: if there is no deinit(), after a softreset the i2c is still configured in whatever mode? If we want to reuse? we reinitiaze? with no impact?

As discusssed, I don´t yet understand how the garbage collector handles destructing all objects... but I don´t see (yet) the connection to hardware peripheral deinitialization. That has to be handled somewhere (freeing before initing() all the time?)...

[NikhitaR-IFX]

Also handles for softI2C?

[jaenrig-ifx]

Nop. The I2CSoft is completely handled by the extmod... (and relying on mp_hal functions). I also wonder if something there are wonder. I understand this works using pins, but I don´t see the gpio initialization being handled anywhere.
Was the softi2c functionally tested?

[IFX-Anusha]

GPIO initialization for the softI2C is handled inside mphalport.c using cyhal_gpio_configure( ) function

[jaenrig-ifx]

Mmm okay, I think then we have to extend that to initialize that pin if not inited already.

[IFX-Anusha]

Initially, we had

from machine import I2C
i2c = I2C(0)

This will do the i2c init with default pins. So that is removed with this right?

[jaenrig-ifx]

Yes, I removed that. There is no such thing as "default" pins unless we provide pre-instantiated objects to those default pins allocation... and that has to be documented in a pinout diagram or table.
For multiple board, this is harder to maintain. But we can have such default allocation, then that comes with a nice pin out diagram and we have to add those to the code. But then the user can happily call i2c = I2C(0) for any board.
In the end, the user needs to know the pins, so we can skip the magic of not providing any (at least for now).

[IFX-Anusha]

okay. sounds good