STM32F3Discovery and Keil Uvision, how can I write to a register?

[jeremy]

Posted on February 08, 2014 at 21:59

I am trying to understand the stm32 at a low level, and I think I understand how most of the registers I need to modify work, but I am looking for some simple C code to write data to a register. Right now I am trying to do something like this:

volatile unsigned int *peripheral;

peripheral=(unsigned int*)GPIO_MODER_MODER9_0; //address I want to write to *peripheral=GPIO_E_start //data I want to put into the register (where I have defined GPIO_e_start as 0x48001000.   When I run this the code goes to the hard fault catcher, and I'm not sure what I'm doing wrong. Ideally I just want a small simple piece of code that allows me to write data to a register, but I have been stuck for a while now without success.

[Tesla DeLorean]

Posted on February 08, 2014 at 22:23

Your logic is entirely backward, GPIO_MODER_MODER9_0 is a value not an address

GPIOE->MODER = GPIO_MODER_MODER9_0; would be what you're looking for. Want to know the address, look to print out &GPIOE->MODER, your address, at first glance also seems to be wrong, as if it where a bit-banded address or something.

[Tesla DeLorean]

Posted on February 08, 2014 at 22:40

volatile unsigned int *peripheral;

peripheral=(unsigned int*)(&GPIOE->MODER); // 0x48001000, cross checked *peripheral=GPIO_MODER_MODER9_0;

[dmirsky]

Posted on February 08, 2014 at 22:42

Also, make sure the clock for the peripheral is on and turn off optimizations.

This ran fine for me.     volatile unsigned int *periph = (unsigned int*) 0x40020400;  //GPIOB_MODER     RCC->AHB1ENR |= RCC_AHB1ENR_GPIOBEN;  // Turn on clock.     *periph = 0x0f0f0f0f;

[jeremy]

Posted on February 08, 2014 at 23:20 Thanks a lot! I wonder, did you intend to write AHB1? As far as I can tell from looking at the clock diagrams there's only 1 AHB, and I can't find any ahb1 references in my headers.

[jeremy]

Posted on February 08, 2014 at 23:20 Thanks a ton!

[Tesla DeLorean]

Posted on February 08, 2014 at 23:58

Daniel is probably referring to a different series STM32 with a different mix of APB and AHB, and addresses/placement of GPIO peripherals.