STM32F429的一个很大优势就是可以直接驱动SDRAM，这样一下子就可以外扩可观的运存，很诱惑。
这里用到的SDRAM 为W9825G6KH, 256Mbit， 32MByte

1. 配置CubeMX
   
   这里不展开这里面的数值的具体计算过程，主要是按照手册来算的，感兴趣的可以网上寻找，有很多相关的资料。
2. SDRAM 初始化，SDRAM不像SRAM配置好了就可以用，他需要初始化

#include "stm32f4xx_hal.h"extern SDRAM_HandleTypeDef hsdram1;#define SDRAM_MODEREG_BURST_LENGTH_1             ((uint16_t)0x0000)
#define SDRAM_MODEREG_BURST_LENGTH_2             ((uint16_t)0x0001)
#define SDRAM_MODEREG_BURST_LENGTH_4             ((uint16_t)0x0002)
#define SDRAM_MODEREG_BURST_LENGTH_8             ((uint16_t)0x0004)
#define SDRAM_MODEREG_BURST_TYPE_SEQUENTIAL      ((uint16_t)0x0000)
#define SDRAM_MODEREG_BURST_TYPE_INTERLEAVED     ((uint16_t)0x0008)
#define SDRAM_MODEREG_CAS_LATENCY_2              ((uint16_t)0x0020)
#define SDRAM_MODEREG_CAS_LATENCY_3              ((uint16_t)0x0030)
#define SDRAM_MODEREG_OPERATING_MODE_STANDARD    ((uint16_t)0x0000)
#define SDRAM_MODEREG_WRITEBURST_MODE_PROGRAMMED ((uint16_t)0x0000)
#define SDRAM_MODEREG_WRITEBURST_MODE_SINGLE     ((uint16_t)0x0200)#define SDRAM_BANK1_BASE_ADDRESS    0XC0000000  
#define SDRAM_HALF_WORD_SIZE        0x1000000      //0x1000000 - 16M*16bit =32Mbytevoid SDRAM_Initialization_Sequence(SDRAM_HandleTypeDef *hsdram);
void SDRAM_TEST(void);typedef uint16_t u16;
typedef uint8_t u8;
typedef uint32_t u32;

/*** @brief  Perform the SDRAM exernal memory inialization sequence* @param  hsdram: SDRAM handle* @param  Command: Pointer to SDRAM command structure* @retval NoneSDRAM刷新周期是64ms，行数是8192行，时钟频率是180MHz/2=90MHz所有COUNT = (64ms/8192)/(1/90us)-20 = 64000*90/8192-20 = 683*/
void SDRAM_Initialization_Sequence(SDRAM_HandleTypeDef *hsdram)
{__IO uint32_t tmpmrd = 0;FMC_SDRAM_CommandTypeDef Command;/* Configure a clock configuration enable command */Command.CommandMode 		 = FMC_SDRAM_CMD_CLK_ENABLE;Command.CommandTarget 		 = FMC_SDRAM_CMD_TARGET_BANK1;Command.AutoRefreshNumber 	 = 1;Command.ModeRegisterDefinition = 0;/* Send the command */HAL_SDRAM_SendCommand(hsdram, &Command, 0x1000);/* Insert 10 ms delay */HAL_Delay(10);/* Configure a PALL (precharge all) command */Command.CommandMode 		 = FMC_SDRAM_CMD_PALL;Command.CommandTarget 	     = FMC_SDRAM_CMD_TARGET_BANK1;Command.AutoRefreshNumber 	 = 1;Command.ModeRegisterDefinition = 0;/* Send the command */HAL_SDRAM_SendCommand(hsdram, &Command, 0x1000);/* Configure a Auto-Refresh command */Command.CommandMode 		 = FMC_SDRAM_CMD_AUTOREFRESH_MODE;Command.CommandTarget 		 = FMC_SDRAM_CMD_TARGET_BANK1;Command.AutoRefreshNumber 	 = 8;Command.ModeRegisterDefinition = 0;/* Send the command */HAL_SDRAM_SendCommand(hsdram, &Command, 0x1000);/* Program the external memory mode register */tmpmrd = (uint32_t)SDRAM_MODEREG_BURST_LENGTH_8|SDRAM_MODEREG_BURST_TYPE_SEQUENTIAL   |SDRAM_MODEREG_CAS_LATENCY_3           |SDRAM_MODEREG_OPERATING_MODE_STANDARD |SDRAM_MODEREG_WRITEBURST_MODE_SINGLE;Command.CommandMode = FMC_SDRAM_CMD_LOAD_MODE;Command.CommandTarget 		 = FMC_SDRAM_CMD_TARGET_BANK1;Command.AutoRefreshNumber 	 = 1;Command.ModeRegisterDefinition = tmpmrd;/* Send the command */HAL_SDRAM_SendCommand(hsdram, &Command, 0x1000);/* Set the refresh rate counter *//* (7.81us x Freq) - 20 *//* Set the device refresh counter */HAL_SDRAM_ProgramRefreshRate(hsdram, 683);
}

void SDRAM_TEST(void)
{uint32_t temp = 0;uint16_t err=0;for(i=0;i<SDRAM_HALF_WORD_SIZE;i++){*(__IO uint16_t*)(SDRAM_BANK1_BASE_ADDRESS+2*i) = (uint16_t)i;}for(i=0;i<SDRAM_HALF_WORD_SIZE;i++){temp = 0;temp = *(__IO uint16_t*)(SDRAM_BANK1_BASE_ADDRESS+2*i);if(temp!=(uint16_t)i){err++;}}printf("Total error =%d\n",err);
}

3.MAIN函数中加入即可

SDRAM_Initialization_Sequence();
SDRAM_TEST();//optioanl