Posted on February 20, 2017 at 20:43It 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)
{
}
}
