Could someone explain to me why at function i2c_init (file cpu/stm32/periph/i2c_1.c), the clock is first enabled with periph_clk_en(i2c_config[dev].bus, i2c_config[dev].rcc_mask);, but then later again with I2C_CLOCK_SRC_REG |= i2c_config[dev].rcc_sw_mask ?
And why only for some STM32 families? For example, no G0, G4, U5 and C0.
Without diving into the code myself, I will venture a guess.
It is not uncommon to have to setup the clock going to a peripheral (RCC) as well as the clock signal inside of a peripheral. The RCC is responsible for the clock signal outside of the peripheral itself, but often time peripherals might have registers that select from one of several clock sources, or further dived the clock once inside the peripheral.
Thanks for your response. But looking at the code, isn’t these two line setting the same register to the same value? Or did I misunderstood it?
My understanding is that periph_clk_en sets the i2c_config[dev].bus with the i2c_config[dev].rcc_mask, so if i2c_config[dev].bus == I2C_CLOCK_SRC_REG it is the same operation.
Also why is it only needed for certain STM32 families?