jeandudey
commented
4 years ago I thought about the clock switching too, it's hard to get it right. My thinking about it was that peripherals (and sometimes user code) needs to be informed about clock changes.
Callback mechanism: when clocks change a callback in peripheral drivers is called, allowing them to update state
This introduces another problem for example I2C, that to calculate frequency there are higher and lower bounds for the APB frequency, an update could result in an invalid setting or defaulting to another frequency (min or max) without the user of the HAL getting knowledge of it.
A locking mechanism like used in the esp-idf: when a peripheral needs a fixed clock it acquires a lock . When no locks are acquired the clocks can be dynamically scaled for lower power consumption
This might be a good alternative, since when the peripheral ends using the fixed clock it needs, the clock can go back to the previous configuration.
I haven't tested the code yet on real hardware, I'm trying to get a working rustc for Xtensa. This is really good work.
arjanmels
Gasper
MabezDev
This pull request includes a clock_control, dport and serial peripheral. Also included are two examples (basic serial, and clock control).
In its current state it allows switching clock frequency on the esp32 between Xtal, PLL and internal 8.5MHz clock. Also calculates the CPU, APB, Ref clock and source.
For clock switching the approach used by esp-idf is followed and both locking mechanism (for Dynamic Clock Switching and callbacks are implemented).
It support serial input and output at programmable baudrate.