Support 4.9152MHz clock

[gauravahuja]

Add support for 4.9152MHz clock which also provides error free UART for certain baud rates like 38400

[MCUdude]

That's not a very common clock frequency, and of you have a look at an AVR baud rate calculator, 4.9152 MHz isn't a very "good" clock speed to choose in terms of UART compatibility.

[gauravahuja]

Compare it with baud compatibility for 4Mhz clock. 4.9152Mhz offers 0% error rate for many baud rates that you would realistically use for sub 8Mhz clocks.

[MCUdude]

Yes, but then again 7.3728 MHz is a better option. If you have to use that particular frequency, you can always use PlatformIO.

[gauravahuja]

@MCUdude There are a few things I would like to point out

• Your comment about 4.9152MHz not being very "good" clock speed isn't objectively true compared to other frequencies supported by MiniCore.
• There will always be some clock setup that is better like 7.3728 MHz you suggested. But then what is the point of supporting multiple clock frequencies that are not better?
• Platform IO uses MiniCore as part of its build process so I cannot readily use it without support for clock frequency I need.
• I am willing to invest time and energy into adding support for a new clock frequency If you are willing to include that in MiniCore.

[MCUdude]

Your comment about 4.9152MHz not being very "good" clock speed isn't objectively true compared to other frequencies supported by MiniCore.

True, clock frequencies, like 4 and 8 MHz, perform worse than 4.9152 MHz when using "standard" baud rates like 115200, but performers perfect at non-standard ones like 250000 and 500000.

But then what is the point of supporting multiple clock frequencies that are not better?

It depends on the application. A "round" clock like 4 MHz performs excellent with "round" baud rates, like 250000 baud, like I mentioned earlier.

Platform IO uses MiniCore as part of its build process so I cannot readily use it without support for clock frequency I need.

You can easily override the clock frequency (F_CPU) when building using PlatformIO. PlatformIO is very flexible, much more than Arduino IDE.

I am willing to invest time and energy into adding support for a new clock frequency If you are willing to include that in MiniCore.

But I see no point in adding a new clock frequency to the list when there are better alternatives for both standard and non-standard baud rates. Why not change to a more common frequency rather than pushing toward adding this not-so-common, not-all-that-great clock that isn't very common to use with AVRs?