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STM32F407 debuugger not working when PORTA in use

Question asked by Mark Greally on Oct 10, 2017
Latest reply on Oct 10, 2017 by Mark Greally



Using a STM32F407 I am having an issue using the debugger when PORTA is in use. The debugger works fine when PORTA is not in use. I am using MCO1 which is on PORTA and when I set the MODER register the debugger fails.


    // Enable MCO1 clock on PA8
     GPIOA->MODER = (1 << 17);  // same as *GPIOAMODER = (1 << 17);
     GPIOA->OSPEEDR = 0x30000;  // very high speed. OSPEEDR8
     GPIOA->PUPDR = 0x0;        // No pull-up, pull-down
     GPIOA->AFR[0] = 0x0;       // AF0
     GPIOA->AFR[1] = 0x0;       // AF0


PA8 does not share any pins with the debugger so this should work. Is there some additional settings that need to be set to allow this??