Blink Newbie help debug!

Ok, here is the code in clear text. I don't get the insert code function: 

#include "stm32f407xx.h"

void myDelay(int times){

volatile int i, j;

for (i = 0; i < times; ++i) {

j++;

}

}

void ini(void){

RCC -> AHB1ENR |= RCC_AHB1ENR_GPIOAEN; //enable GPIO clock for AHB og RCC

GPIOA -> MODER |= GPIO_MODER_MODER6_0 |GPIO_MODER_MODER7_0;

GPIOA -> OTYPER &= ~(GPIO_OTYPER_OT_7|GPIO_OTYPER_OT_6);

GPIOA -> OSPEEDR |= GPIO_OSPEEDER_OSPEEDR7_1 | GPIO_OSPEEDER_OSPEEDR6_1; //High speed 10

GPIOA -> PUPDR &= ~(GPIO_PUPDR_PUPDR7 | GPIO_PUPDR_PUPDR6);

}

int main(void)

{

void ini();

    while(1)

    {

    GPIOA -> BSRRL |= 0x000000C0; //Bit Set 6 & 7

    myDelay(200000);

    GPIOA -> BSRRL |= 0x00C00000; //Bit 6 & 7 reset

    myDelay(200000);

    }

    return 0;

}

Hi Ole.

Welcome to the ARM Cortex-M world! :)

As you're coming from AVR, you're not used to that you need to switch on things, before they work.

This is something you'll need to get used to.

Each time you experience that a peripheral does not seem to work, you'll need to ask yourself:  "Have I turned on all the peripherals I'm using in the RCC?".

In this case, you will need to turn on the GPIO clock power.

That's done with something like this...

RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN;

As you see, the name of the bitmask is (quite cleverly) constructed from the peripheral being written to, then the register and finally the contents of that register.

You should be able to find the details in RM0090 and the STM32F407 datasheet. :)

-But why oh why is this so complicated - couldn't the peripherals just be turned on from the beginning ?

The answer is that if they were, every Cortex-M would use a lot of power as soon as it's turned on; in most situations, this is undesirable; especially when running on battery power (whether it be a CR2032 backup-battery or a couple of 1.2V batteries).

-So you'll have to remember to turn on the power-switch before you can expect light. ;)

All peripherals need clock power, including (but not limited to) timers, DMA, GPIO, SPI, I2C, RTC, SD/MMC - yes, even RAM and Flash.

By default, Flash and RAM is turned on.