"_begin"-function is public

[Adminius]

for more flexibility declare _begin as public

allows experienced user use almost any pin.

Example:
_begin(&sercom4, SERCOM4, SERCOM4_DMAC_ID_TX, 22, SPI_PAD_0_SCK_3, PIO_SERCOM_ALT);

Based on discussion in #1, #5, #14 , #17

P.S. we can also rename _begin to begin...

[PaintYourDragon]

The only explanation I can find for why there’s a protected _begin() function comes from a note with commit #10 that it “ought not be called by anyone.” Apparently there’s a legit use case, and I seem to vaguely recall us even using it somewhere, so maybe that wasn’t the best choice.

Also prior to #10, it appeared as an overloaded case of begin(), not a distinct _begin() function. I’m all for restoring the original behavior — a special overloaded begin() case, not a separate _begin(). Most folks will never even know the special case exists and would go on using the stock begin(), advanced folks can use the special variant.

Yes, all cases of boolean can be replaced with bool now. boolean was an oldschool Arduino compatibility thing and is no longer needed.

clang-format seems to be complaining about a single blank line that can be deleted, see “Details” accompanying the build process above.

[Adminius]

Hi @PaintYourDragon, I've made changes according to your suggestions.

[Adminius]

@ladyada are you ok with this PR?

[ladyada]

sure!