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STM32F407ZGT, SPI3 and Debugging with SWD

Question asked by kunz.martin.002 on Jan 12, 2015
Latest reply on Jan 20, 2015 by kunz.martin.002

i'm using an STM32F407ZET6 with SPI1, SPI2, SP3 and SWD.
SPI1 and SPI2 are always working fine.
SPI3 works when the CPU is running without debugging.
Whenever I set a breakpoint SPI3 Clock (PortB3) has strange pulses.
I checked how to disable JTAG on STM32F4 in RM0090. It shoud be done automatically when
Changing the Pin Configuration:
GIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
And changing the Alternate Function mapping:
GPIO_PinAFConfig(SCK->GetPort(), SCK->GetPinSource(), GPIO_AF_SPI3);

Both is done in my code and as SPI3 is working (logic analizer and SPI-Chip is responding) as long as I break debugging via breakpoint or halt.

However when I set a breakpoint SPI3 fails as SCK outputs something. I can also see that AFRL3 is always changed back to 0 and OSPEEDR3 is always changed back to 3.
Can anybody give me advice how to solve this issue?