STM32F411 - common short questions ...

[timbo2023]

Good Evening Ladies and Gentlemen,

A short introducing purpose of mine:

int main(void)
{
RCC->AHB1ENR |= 0xFC;             // ---> Here I would like to open the Port clock
RCC->APB1ENR |= 0xFC;             // ---> Here I would like to open the USART2 clock - in this context not relevant

GPIOA->MODER |= 0x55555555;       // ---> Here I define Port A as output
GPIOC->MODER |= 0x55555555;       // ---> Here I define Port C as output

GPIOA->ODR |= (1<<2);             // ---> Here I would like to set PA2 "high"

GPIOC->ODR |= (1<<13);            // ---> Here I would like to set the onboard LED (PC13) "high"

while(1) {
GPIOA->ODR |= (1<<0);             // Here I would like to "toggle" PA0 and PA6  
GPIOA->ODR |= (1<<6);
delayMs(50);                      // It only is a not relevant "delay" for this purpose

GPIOA->ODR &= ~(1<<0);
GPIOA->ODR &= ~(1<<6);
delayMs(50);
}
}

But something went wrong - it does not work - Do you have any suggestions especially regarding a simple "toggling"?

It should be a pre work for a stepper motor controlling.

Best regards

~TIMBO~

[waclawek.jan]

RMW is an abbreviation (acronym) from Read-Modify-Write.

For example, if you write

GPIOA->ODR |= (1<<0);

that is a Read-Modify-Write operation, because:

- first, the processor reads in content of GPIOA->ODR register into some of its internal working registers

- then the processor performs the bitwise-OR operation with (1 << 0), that's the modify part

- and finally, processor writes from internal register into GPIOA->ODR the modified value

JW

[timbo2023]

And that is only possible with a BSRR register?

[timbo2023]

In spite of it - I would like to set A2 and A6 as "high" - and toggle with the ODR register A0.

Could you write shortly the mode register setting, too?

[waclawek.jan]

Don't use "A0" etc. It's PA0, PA2 and PA6. "A0" may cause confusion with Arduino-connector signal marking.

For PA0 to be set as output, you have to set bits 0 and 1 of GPIOA_MODER to 0b01.

For PA2 to be set as output, you have to set bits 4 and 5 of GPIOA_MODER to 0b01.

For PA6 to be set as output, you have to set bits 12 and 13 of GPIOA_MODER to 0b01.

You may see a pattern and write macros/functions accordingly.

I recommend to try it without writing any program (maybe an infinite loop), by directly writing to registers in the debugger.

Then, to set pin PA0 high, write 1 into bit 0 of GPIOA_BSRR. This has to be a direct write, not a RMW with OR:

GPIOA->BSRR = (1 << 0);

To set pin PA2 high, write 1 into bit 2 of GPIOA_BSRR:

GPIOA->BSRR = (1 << 2);

To set pin PA6 high, write 1 into bit 6 of GPIOA_BSRR:

GPIOA->BSRR = (1 << 6);

To set pin PA0 to low, write 1 into bit 16 of GPIOA_BSRR:

GPIOA->BSRR = (1 << (0 + 16));

To set pin PA2 to low, write 1 into bit 18 of GPIOA_BSRR:

GPIOA->BSRR = (1 << (2 + 16));

To set pin PA6 to low, write 1 into bit 22 of GPIOA_BSRR:

GPIOA->BSRR = (1 << (6 + 16));

You may have spotted a pattern here, too; again, try to write a macro or a function.

You may want to read this intro.

JW

[timbo2023]

RCC->AHB1ENR |= (1<<0)|(1<<2);  // enable A and C port
RCC->APB1ENR |= (1<<17); // enable USART2

GPIOA->MODER |= (1<<0)|(1<<4)|(1<<12); // set A0, A2, A6 as output
GPIOC->MODER |= (1<<26); // set PC13 as output

GPIOA->BSRR = (1 << 2);
GPIOA->BSRR = (1 << 6);

GPIOC->BSRR = (1 << (13 + 16));

while (1)
{
	GPIOA->BSRR = (1 << 0);
	delayMs(50);

	GPIOA->BSRR = (1 << (0 + 16));
	delayMs(50);
}

Thank you for your answer.

Result:

PC13 is glowing

PA0 "toggled" - but the stepper motor does not drive... thank you in spite of it ...

[timbo2023]

Perhaps for interested people, my trial-stand for controlling a stepper motor ...

But the stepper motor does not drive at the moment ...