3楼正确,的确存在竟争
谢谢浪淘沙的文档，的确很及时 ^o^
DMA 控制器和 Cortex-M3 核共享系统数据线执行直接存储器数据传输。因此，1 个 DMA
请求占用至少 2个周期的 CPU访问系统总线时间。为了保证 Cortex-M3核的代码执行的最
小带宽，DMA控制器总是在 2个连续的DMA请求间释放系统时钟至少1个周期。
可是spi相对指命来说，是很慢的设备，问题肯定不在这里。我贴出代码，浪淘沙可有空帮忙解决？ xixi
代码是demo中的，只在Demo_Init函数未尾增加了SPI DMA的代码。
int main(void)
{
#ifdef DEBUG
debug();
#endif
/* Initialize the Demo */
Demo_Init();
while(1);
}
void Demo_Init(void)
{
SPI_InitTypeDef SPI_InitStructure;
DMA_InitTypeDef DMA_InitStructure;
unsigned char SPI1_Buffer_Rx[128];
unsigned char SPI1_Buffer_Tx[128];
/* SYSCLK, HCLK, PCLK2 and PCLK1 configuration -----------------------------*/
/* RCC system reset(for debug purpose) */
RCC_DeInit();
/* Enable HSE */
RCC_HSEConfig(RCC_HSE_ON);
/* Wait till HSE is ready */
HSEStartUpStatus = RCC_WaitForHSEStartUp();
if(HSEStartUpStatus == SUCCESS)
{
/* HCLK = SYSCLK */
RCC_HCLKConfig(RCC_SYSCLK_Div1);
/* PCLK2 = HCLK */
RCC_PCLK2Config(RCC_HCLK_Div1);
/* PCLK1 = HCLK/2 */
RCC_PCLK1Config(RCC_HCLK_Div2);
/* ADCCLK = PCLK2/6 */
// RCC_ADCCLKConfig(RCC_PCLK2_Div6);
/* Flash 2 wait state */
FLASH_SetLatency(FLASH_Latency_2);
/* Enable Prefetch Buffer */
FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
/* PLLCLK = 8MHz * 9 = 72 MHz */
RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);
/* Enable PLL */
RCC_PLLCmd(ENABLE);
/* Wait till PLL is ready */
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)
{
}
/* Select PLL as system clock source */
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
/* Wait till PLL is used as system clock source */
while(RCC_GetSYSCLKSource() != 0x08)
{
}
}
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB |
RCC_APB2Periph_SPI1, ENABLE);
/* Enable GPIOA, GPIOB, GPIOC, GPIOD, GPIOE and AFIO clocks */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB |RCC_APB2Periph_GPIOC
| RCC_APB2Periph_GPIOD | RCC_APB2Periph_GPIOE | RCC_APB2Periph_AFIO, ENABLE);
/* TIM1 Periph clock enable */
// RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);
/* SPI2 Periph clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE);
/* TIM2 and TIM4 clocks enable */
// RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2 | RCC_APB1Periph_TIM4, ENABLE);
/* USBCLK = PLLCLK/1.5 */
// RCC_USBCLKConfig(RCC_USBCLKSource_PLLCLK_1Div5);
/* Enable USB clock */
// RCC_APB1PeriphClockCmd(RCC_APB1Periph_USB, ENABLE);
/*------------------- Resources Initialization -----------------------------*/
/* GPIO Configuration */
GPIO_Config();
/* Interrupt Configuration */
InterruptConfig();
/* Configure the systick */
SysTick_Config();
/*------------------- Drivers Initialization -------------------------------*/
/* Initialize the LEDs toogling */
LedShow_Init();
/* Initialize the Low Power application */
LowPower_Init();
/* If HSE is not detected at program startup */
if(HSEStartUpStatus == ERROR)
{
/* Generate NMI exception */
NVIC_SetSystemHandlerPendingBit(SystemHandler_NMI);
}
/* Initialize the SPI FLASH driver */
SPI_FLASH_Init();
// MSD_Init();
#if 1
/* Test for SPI DMA function */
#define CRCPolynomial 7
#define SPI1_DR_Address 0x4001300C
#define BufferSize 128
/* 初始化SPI1 ------------------------------------------------------*/
SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
SPI_InitStructure.SPI_Mode = SPI_Mode_Master;
SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;
SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;
SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;
SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_8;
SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
SPI_InitStructure.SPI_CRCPolynomial = CRCPolynomial;
SPI_Init(SPI1, &SPI_InitStructure);
/* 初始化DMA Channel2 ----------------------------------------------*/
DMA_DeInit(DMA_Channel2);
DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)SPI1_DR_Address;
DMA_InitStructure.DMA_MemoryBaseAddr = (u32)SPI1_Buffer_Rx;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize = BufferSize;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA_Channel2, &DMA_InitStructure);
/* DMA Channel3 configuration ----------------------------------------------*/
DMA_DeInit(DMA_Channel3);
DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)SPI1_DR_Address;
DMA_InitStructure.DMA_MemoryBaseAddr = (u32)SPI1_Buffer_Tx;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
DMA_InitStructure.DMA_Priority = DMA_Priority_Low;
DMA_Init(DMA_Channel3, &DMA_InitStructure);
/* Enable SPI1 DMA Rx request */
SPI_DMACmd(SPI1, SPI_DMAReq_Tx, ENABLE);
SPI_DMACmd(SPI1, SPI_DMAReq_Rx, ENABLE);
/* Enable SPI1 CRC calculation */
SPI_CalculateCRC(SPI1, ENABLE);
/* Enable SPI1 */
SPI_Cmd(SPI1, ENABLE);
DMA_Cmd(DMA_Channel2, ENABLE);
DMA_Cmd(DMA_Channel3, ENABLE);
/* Transfer complete */
while(!DMA_GetFlagStatus(DMA_FLAG_TC2));
#endif
/* Enable Leds toggling */
LedShow(ENABLE);
} |
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