Missing setDefaultFrequency() for Wire.begin() cleanup

[FStefanni]

Hi,

I am looking for a way to cleanup the call to Wire.begin(), as described in the issue #3779,
i.e. to set all relevant parameter before calling the begin() method.
At the moment, I see that the pins can be set with a call to setPins(), which is fine,
but we are missing an equivalent method to set the last parameter, i.e. the frequency.

I have seen the setClock() method, but for what I understand, calling it is not exactly the same, for example:

• it seems that we cannot just pass 0 to set the default frequency
• it actually does the frequency configuration, whilst we just want to set a default parameter for the future

Thus, I believe that adding a support method (e.g. setDefaultFrequency(), accepting also zero as default value), would be great,
since imho it will complete/refine the stuff of issue #3779. This change requires also some other code changes to manage the default frequency, where needed in the rest of the TwoWire class code.

Regards.

[SuGlider]

@FStefanni - Wire has been refactored.
As you can see, Wire::begin() overload is OK (#7000) and Wire::setClock() takes zero as argument and sets the I2C Frequency to the default 100KHz.
https://github.com/espressif/arduino-esp32/blob/master/libraries/Wire/src/Wire.cpp#L272-L293
https://github.com/espressif/arduino-esp32/blob/master/cores/esp32/esp32-hal-i2c.c#L267-L271