外部内存分配SDRAM

发布于 2020-09-18 14:06:04 浏览：1435 订阅该版

2 个回答

RXGC_5534 2020-09-18

这家伙很懒，什么也没写！

YMQQ_3390 2021-05-15

这家伙很懒，什么也没写！

先在.s文件 里面添加FSMC_SRAM_Init()函数，实现外部SDRAM的初始化如下图：
![s文件添加代码.png](https://oss-club.rt-thread.org/uploads/20210515/0a7c178e9671a84d82dcead7162fc004.png)
然后在初始化的时候先调用
```c
rt_system_heap_init((void *)HEAP_BEGIN, (void *)HEAP_END);
```
初始化内部SRAM，然后调用
```
rt_memheap_init(&system_heap,"sdram",(void *)0x68000000,0x100000);
```
将外部SDRAM挂载到heap_map里面。编译下载后，就可以用rt_malloc等接口了。
FSMC_SRAM_Init()如下：
```c
void FSMC_SRAM_Init(void)
{
	/*-- GPIOs Configuration -----------------------------------------------------*/
	/* Enable GPIOD, GPIOE, GPIOF and GPIOG interface clock */
	RCC->AHB1ENR   |= 0x00000078;
	
	//PD0,1,4,5,8~15    100M AF OUT_PP UP
	//PE0,1,7~15        100M AF OUT_PP UP
	//PF0~5,12~15       100M AF OUT_PP UP
	//PG0~5,10          100M AF OUT_PP UP
	
	/* Connect PDx pins to FMC Alternate function */
	GPIOD->AFR[0]  = 0x00CC00CC;
	GPIOD->AFR[1]  = 0xCCCCCCCC;
	/* Configure PDx pins in Alternate function mode */  
	GPIOD->MODER   = 0xAAAA0A0A;
	/* Configure PDx pins speed to 100 MHz */  
	GPIOD->OSPEEDR = 0xFFFF0F0F;
	/* Configure PDx pins Output type to push-pull */  
	GPIOD->OTYPER  = 0x00000000;
	/* pull-up for PDx pins */ 
	GPIOD->PUPDR   = 0x55550505;
	
	/* Connect PEx pins to FMC Alternate function */
	GPIOE->AFR[0]  = 0xC00000CC;
	GPIOE->AFR[1]  = 0xCCCCCCCC;
	/* Configure PEx pins in Alternate function mode */ 
	GPIOE->MODER   = 0xAAAA800A;
	/* Configure PEx pins speed to 100 MHz */ 
	GPIOE->OSPEEDR = 0xFFFFC00F;
	/* Configure PEx pins Output type to push-pull */  
	GPIOE->OTYPER  = 0x00000000;
	/* pull-up for PEx pins */ 
	GPIOE->PUPDR   = 0x55554005;
	
	/* Connect PFx pins to FMC Alternate function */
	GPIOF->AFR[0]  = 0x00CCCCCC;
	GPIOF->AFR[1]  = 0xCCCC0000;
	/* Configure PFx pins in Alternate function mode */   
	GPIOF->MODER   = 0xAA000AAA;
	/* Configure PFx pins speed to 100 MHz */ 
	GPIOF->OSPEEDR = 0xFF000FFF;
	/* Configure PFx pins Output type to push-pull */  
	GPIOF->OTYPER  = 0x00000000;
	/* pull-up for PFx pins */ 
	GPIOF->PUPDR   = 0x55000555;
	
	/* Connect PGx pins to FMC Alternate function */
	GPIOG->AFR[0]  = 0x00CCCCCC;
	GPIOG->AFR[1]  = 0x00000C00;
	/* Configure PGx pins in Alternate function mode */ 
	GPIOG->MODER   = 0x00200AAA;
	/* Configure PGx pins speed to 100 MHz */ 
	GPIOG->OSPEEDR = 0x00300FFF;
	/* Configure PGx pins Output type to push-pull */  
	GPIOG->OTYPER  = 0x00000000;
	/* pull-up for PGx pins */ 
	GPIOG->PUPDR   = 0x00100555;
	
	/*-- FMC/FSMC Configuration --------------------------------------------------*/
	/* Enable the FMC/FSMC interface clock */
	RCC->AHB3ENR         |= 0x00000001;
	
	//寄存器清零
	//bank1有NE1~4,每一个有一个BCR+TCR，所以总共八个寄存器。
	//这里我们使用NE3 ，也就对应BTCR[4],[5]。        
	FSMC_Bank1->BTCR[4]=0X00000000;
	FSMC_Bank1->BTCR[5]=0X00000000;
	FSMC_Bank1E->BWTR[4]=0X00000000;
	//操作BCR寄存器 使用异步模式,模式A(读写共用一个时序寄存器)
	//BTCR[偶数]:BCR寄存器;BTCR[奇数]:BTR寄存器
	FSMC_Bank1->BTCR[4]|=1<<12;//存储器写使能
	FSMC_Bank1->BTCR[4]|=1<<4; //存储器数据宽度为16bit      
	//操作BTR寄存器   （HCLK=168M, 1个HCLK=6ns       
	FSMC_Bank1->BTCR[5]|=8<<8; //数据保持时间（DATAST）为9个HCLK 6*9=54ns    
	FSMC_Bank1->BTCR[5]|=0<<4; //地址保持时间（ADDHLD）未用到     
	FSMC_Bank1->BTCR[5]|=0<<0; //地址建立时间（ADDSET）为0个HCLK 0ns    
	//闪存写时序寄存器  
	FSMC_Bank1E->BWTR[4]=0x0FFFFFFF;//默认值
	//使能BANK1区域3
	FSMC_Bank1->BTCR[4]|=1<<0;
}
```