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stm32/sdram: Add SDRAM enter/leave self-refresh mode functions.

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These functions enable SDRAM data retention in stop mode.  Example usage,
in mpconfigboard.h:

    #define MICROPY_BOARD_ENTER_STOP sdram_enter_low_power();
    #define MICROPY_BOARD_LEAVE_STOP sdram_leave_low_power();
This commit is contained in:
iabdalkader 2020-12-08 01:55:50 +02:00 committed by Damien George
parent 32d76e5de6
commit b603066bc2
2 changed files with 22 additions and 2 deletions
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22
ports/stm32/sdram.c
View File

@ -49,8 +49,7 @@
#ifdef FMC_SDRAM_BANK
static void sdram_init_seq(SDRAM_HandleTypeDef
*hsdram, FMC_SDRAM_CommandTypeDef *command);
static void sdram_init_seq(SDRAM_HandleTypeDef *hsdram, FMC_SDRAM_CommandTypeDef *command);
extern void __fatal_error(const char *msg);
bool sdram_init(void) {
@ -254,6 +253,25 @@ static void sdram_init_seq(SDRAM_HandleTypeDef
#endif
}
void sdram_enter_low_power(void) {
// Enter self-refresh mode.
// In self-refresh mode the SDRAM retains data with external clocking.
FMC_SDRAM_DEVICE->SDCMR |= (FMC_SDRAM_CMD_SELFREFRESH_MODE | // Command Mode
FMC_SDRAM_CMD_TARGET_BANK | // Command Target
(0 << 5U) | // Auto Refresh Number -1
(0 << 9U)); // Mode Register Definition
}
void sdram_leave_low_power(void) {
// Exit self-refresh mode.
// Self-refresh mode is exited when the device is accessed or the mode bits are
// set to Normal mode, so technically it's not necessary to call this functions.
FMC_SDRAM_DEVICE->SDCMR |= (FMC_SDRAM_CMD_NORMAL_MODE | // Command Mode
FMC_SDRAM_CMD_TARGET_BANK | // Command Target
(0 << 5U) | // Auto Refresh Number - 1
(0 << 9U)); // Mode Register Definition
}
bool sdram_test(bool fast) {
uint8_t const pattern = 0xaa;
uint8_t const antipattern = 0x55;

2
ports/stm32/sdram.h
View File

@ -11,5 +11,7 @@
bool sdram_init(void);
void *sdram_start(void);
void *sdram_end(void);
void sdram_enter_low_power(void);
void sdram_leave_low_power(void);
bool sdram_test(bool fast);
#endif // __SDRAM_H__