STM32F3 GPIO Bit-banding question

[giwonKIM]

Hello, I have purchased and used the NUCLEO-F303RE board.

I am trying to control the LED (PA5) using bit-banding.

With reference to the reference manual, I confirmed that the address of GPIOA starts from 0x48000000.

Then, I found and read the PM0214 document, which seems to say that only Peripheral in the area of 0x40000000-0x400FFFFF can be controlled.

So you are saying that my f303re board can't control gpio using bit_banding? And if so, how can I control it directly? Thank you.

 

This is my code.

 

/*
 * bitband.h
 *
 * Created on: Jul 23, 2025
 * Author: giwon30
 */

#ifndef INC_BITBAND_H_
#define INC_BITBAND_H_

#include "main.h"


//giwon 250723
//bit banding
//STM32F303RC


#define GPIO_PORT_A 0x48000000UL // GPIOA 베이스 주소
#define FIXED_GPIO_PIN_5 5 // PA5 핀
// GPIOA의 ODR 레지스터 주소 (출력 데이터)
#define GPIOA_ODR (GPIO_PORT_A + 0x14)


// 비트밴딩 별칭 영역 매크로 정의 (SRAM 영역)
#define BITBAND_SRAM_BASE 0x40000000UL
#define BITBAND_SRAM_ALIAS_BASE 0x42000000UL

// 비트밴딩 주소 계산 매크로
#define BITBAND_SRAM(address, bit) (BITBAND_SRAM_ALIAS_BASE + ((address - BITBAND_SRAM_BASE) * 32) + (bit * 4))
#define GPIOA_ODR	(GPIO_PORT_A + 0x14)

#endif /* INC_BITBAND_H_ */



*(volatile uint32_t*)BITBAND_SRAM(GPIOA_ODR, FIXED_GPIO_PIN_5) = 1; // LED ON

[Andrew Neil]

---

@giwonKIM wrote:

how can I control it directly?

What do you mean by "directly" here?

You can use the BSRR (Bit Set and Reset) or BRR (Bit Reset) registers ?

 

[giwonKIM]

I talked about the method.

Can't I control it using bit-banding other than that?

Because I want to control GPIO ASAP.

[Andrew Neil]

I was answering your "If so, ..." question.

You can also drive GPIO via DMA...

 

[TDK]

The BSRR register was created to control a pin without affecting other pins.

 

To turn PA5 on:

GPIOA->BSRR = 1 << 5;

To turn PA5 off:

GPIOA->BSRR = 1 << (5 + 16);

 

[Tesla DeLorean]

It's also a SINGULAR write, not RMW (Read Modify Write) which is going to have significant delay, think write-buffers and in-order completion over the AHB/APB busses.

Bit-Banding isn't remotely more efficient, it just hides the RMW action, but has a lot of hazards of it's own, like clearing TIM->SR bits. It's perhaps best only used on RAM memory variables, as a means to force atomic interaction, which isn't possible in peripheral space as they operated independently / concurrently via own internal combinational and synchronous logic.

The BSRR is the approved, desirable way to do single or multi-bit changes to the GPIO pins on the bank, and without interfering with uninvolved pins.

Usable with 32-bit word DMA from pattern buffers.