又遇怪事，STM32 IAR优化产生的SPI问题

只看该作者 · 2010-7-21 14:40

硬件相同，甚至板子都没掉电，只是换用不同的优化重新仿真，使用IAR高度优化时SPI1的SCK无波形：高度优化时：

中度优化时：

程序:
/****************************************************************************
* 名称：u8 SPI_SendByte(u8 dat)
* 功能：通过SPI发送数据并获取返回数据
* 入口参数：dat
需发送的字节数据
* 出口参数：返回
接收到的数据
* 说明：不采用DMA，仅用于小量数据时
* 调用方法：rdat = SPI_SendByte(0x55);
****************************************************************************/
u8 SPI_SendByte(u8 dat)
{

u8 tmp;


if (SPI1->SR & SPI_I2S_FLAG_OVR)
// 发生溢出错误

tmp = SPI1->DR;
// 读一次DR，清除OVR错误


while(!(SPI1->SR & SPI_I2S_FLAG_TXE));

SPI1->DR = dat;


while(!(SPI1->SR & SPI_I2S_FLAG_RXNE));

return (SPI1->DR);
}

初始化部分：

// 允许SPI1,GPIOA时钟

RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1 | RCC_APB2Periph_GPIOA,ENABLE);

// 允许DMA1时钟

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

/* Configure SPI1 pins: SCK, MISO and MOSI */

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_6 | GPIO_Pin_7;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

GPIO_Init(GPIOA, &GPIO_InitStructure);

/* Deselect the FLASH: Chip Select high */

FLASH_Deselect();

FLASH_WPEnable();

LCD_Deselect();

/* SPI1 configuration */

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_High;

SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;

SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;

SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_16;
// SSD1305 SCK <= 4MHz  73.728/16=4.608MHz

SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;

SPI_InitStructure.SPI_CRCPolynomial = 7;

SPI_Init(SPI1, &SPI_InitStructure);

// 允许收发DMA

SPI_I2S_DMACmd(SPI1, SPI_I2S_DMAReq_Tx | SPI_I2S_DMAReq_Rx, ENABLE);

// 允许DMA完成中断

NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel2_IRQn;
// SPI1 RX

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel3_IRQn;
// SPI1 TX

NVIC_Init(&NVIC_InitStructure);

// 允许SPI

SPI_Cmd(SPI1, ENABLE);