another bit band question

[John Doe1]

Posted on February 20, 2017 at 20:08

hey everyone,

i was using stm32f103 and i was doing a bit-band on gpioa. Now i'm trying on cortex-m4 stm32L432 with no luck. Something changed in L4? Has onyone used bigbanding on gpioa @ stm32l4?

thanks in advance

#bit-band #bit-banding #stm32l4

[S.Ma]

Posted on February 20, 2017 at 20:26

The programming manual is for F4 and L4 and I've used bitbanding for GPIO on the STM32F437.

Maybe the register location is different?

Recently I refrained to use bitband as it seems deprecated on STM32F7. (portability)

Overall, with the BSSR register on STM32, bit band is less important.

[John Doe1]

Posted on February 20, 2017 at 20:30

Thanks for reply!

Maybe i'm doing something wrong..... wierd. What address you used for gpioa, pin 7?

[S.Ma]

Posted on February 20, 2017 at 20:43

It was few years back... found this piece of code from std library for F4: (my original code is somewhere in my archive...)

♯ include 'stm32f4xx.h'

/** @addtogroup STM32F4xx_StdPeriph_Examples

* @{

*/

/** @addtogroup CortexM_BitBand

* @{

*/

♯ define Var_ResetBit_BB(VarAddr, BitNumber) \

(*(__IO uint32_t *) (SRAM_BB_BASE | ((VarAddr - SRAM_BASE) << 5) | ((BitNumber) << 2)) = 0)

♯ define Var_SetBit_BB(VarAddr, BitNumber) \

(*(__IO uint32_t *) (SRAM_BB_BASE | ((VarAddr - SRAM_BASE) << 5) | ((BitNumber) << 2)) = 1)

♯ define Var_GetBit_BB(VarAddr, BitNumber) \

(*(__IO uint32_t *) (SRAM_BB_BASE | ((VarAddr - SRAM_BASE) << 5) | ((BitNumber) << 2)))

__IO uint32_t Var, VarAddr = 0, VarBitValue = 0;

int main(void)

{

/*!< At this stage the microcontroller clock setting is already configured,

this is done through SystemInit() function which is called from startup

files (startup_stm32f40_41xxx.s/startup_stm32f427_437xx.s/startup_stm32f429_439xx.s)

before to branch to application main.

To reconfigure the default setting of SystemInit() function, refer to

system_stm32f4xx.c file

*/

Var = 0x00005AA5;

/* A mapping formula shows how to reference each word in the alias region to a

corresponding bit in the bit-band region. The mapping formula is:

bit_word_addr = bit_band_base + (byte_offset x 32) + (bit_number + 4)

where:

- bit_word_addr: is the address of the word in the alias memory region that

maps to the targeted bit.

- bit_band_base is the starting address of the alias region

- byte_offset is the number of the byte in the bit-band region that contains

the targeted bit

- bit_number is the bit position (0-7) of the targeted bit */

/* Get the variable address --------------------------------------------------*/

VarAddr = (uint32_t)&Var;

/* Modify variable bit using bit-band access ---------------------------------*/

/* Modify Var variable bit 0 -----------------------------------------------*/

Var_ResetBit_BB(VarAddr, 0); /* Var = 0x00005AA4 */

Var_SetBit_BB(VarAddr, 0); /* Var = 0x00005AA5 */

/* Modify Var variable bit 11 ----------------------------------------------*/

Var_ResetBit_BB(VarAddr, 11); /* Var = 0x000052A5 */

/* Get Var variable bit 11 value */

VarBitValue = Var_GetBit_BB(VarAddr, 11); /* VarBitValue = 0x00000000 */

Var_SetBit_BB(VarAddr, 11); /* Var = 0x00005AA5 */

/* Get Var variable bit 11 value */

VarBitValue = Var_GetBit_BB(VarAddr, 11); /* VarBitValue = 0x00000001 */

/* Modify Var variable bit 31 ----------------------------------------------*/

Var_SetBit_BB(VarAddr, 31); /* Var = 0x80005AA5 */

/* Get Var variable bit 31 value */

VarBitValue = Var_GetBit_BB(VarAddr, 31); /* VarBitValue = 0x00000001 */

Var_ResetBit_BB(VarAddr, 31); /* Var = 0x00005AA5 */

/* Get Var variable bit 31 value */

VarBitValue = Var_GetBit_BB(VarAddr, 31); /* VarBitValue = 0x00000000 */

while (1)

{

}

}