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roboterclubaachen / xpcc

DEPRECATED, use our successor library https://modm.io instead
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STM32F7 in non-reset config after DFU mode #205

Closed strongly-typed closed 7 years ago

strongly-typed commented 7 years ago

Hi guys,

while exploring STM32F7 support, we (@daniel-k) discovered that the DFU bootloader leaves the processor in a non-reset configuration, e.g. USART1 is clocked from PCLK2, instead of ABP2. See RCC->DCKCFGR2.

This leads to incorrect baud rates when using xpcc.

What is the best place to reset RCC->DCKCFGR2 to reset defaults? Is it either in the clock config code, or like xpcc_gpio_enable() in startup.c?

Meta: There may be other configurations which differ from reset-configuration when using the DFU. What assumptions does xpcc make about state of the processor?

Any suggestions appreciated.

salkinium commented 7 years ago

This would be done here at the very beginning of the startup script. It'll likely be split into two functions in the future, but don't worry about that for now.

What assumptions does xpcc make about state of the processor?

Power-on reset, which can differ significantly from a debugger reset or when the device resets itself (like DFU). Not sure what to do about that, didn't come up until now.

salkinium commented 7 years ago

Though technically this is also an issue with the ClockControl Implementation that does not correctly configure this bit. This could be solved with #39.