RT-Thread学习笔记八

--------USART DMA方式发送

老规矩，首先说一下我的配置

STM32F207IGT6   MDK   RTT 1.1.0

使用UART2作为finsh组件，UART3作为串口输出

/* register uart2 */

rt_hw_serial_register(&uart2_device,"uart2",RT_DEVICE_FLAG_RDWR| RT_DEVICE_FLAG_INT_RX | RT_DEVICE_FLAG_STREAM,&uart2);

配置成中断接收，数据流发送。

/* register uart3 */

rt_hw_serial_register(&uart3_device,"uart3",RT_DEVICE_FLAG_RDWR| RT_DEVICE_FLAG_INT_RX | RT_DEVICE_FLAG_DMA_TX,&uart3);

配置成中断接收，DMA发送

相信大家已经能够正常使用finsh组件了，所以小弟就不献丑了，呵呵！

shaolin前辈写的finsh的使用

连接1

rt-thread下的串口驱动程序分析

连接2

主要写一下UART3 使用DMA发送

#ifdef RT_USING_UART3

struct stm32_serial_int_rx uart3_int_rx;

struct stm32_serial_dma_tx uart3_dma_tx;

struct stm32_serial_device uart3 =

{

USART3,

&uart3_int_rx,

&uart3_dma_tx

};

struct rt_device uart3_device;

#endif

我仍然按照usart.c中rt_hw_usart_init()的顺序进行分析

/************************************ ******************************/

首先时钟配置RCC_Configuration();

#ifdef RT_USING_UART3

/* Enable USART3 and GPIOC clocks */

RCC_AHB1PeriphClockCmd(UART3_APBPeriph_GPIOX, ENABLE);

RCC_APB1PeriphClockCmd(RCC_APBPeriph_UART3, ENABLE);

RCC_AHB1PeriphClockCmd(RCC_APBPeriph_UART3_DMA,ENABLE);

#endif

配置参数时都采用宏定义，如UART3_APBPeriph_GPIOX，RCC_APBPeriph_UART3，之所以不直接采用ST官方的参数，是因为这样不仅方便以后程序的移植，而且不容易出错。

#define UART3_GPIO_RX                GPIO_Pin_11

#define UART3_GPIO_TX                GPIO_Pin_10

#define UART3_GPIO                        GPIOC

#define UART3_APBPeriph_GPIOX        RCC_AHB1Periph_GPIOC

#define UART3_TX_PinSource GPIO_PinSource10

#define UART3_RX_PinSource GPIO_PinSource11

#define RCC_APBPeriph_UART3        RCC_APB1Periph_USART3

#define RCC_APBPeriph_UART3_DMA RCC_AHB1Periph_DMA1

#define UART3_TX_DMAy_Streamx DMA1_Stream3

#define UART3_TX_DMA_Channel DMA_Channel_4

#define UART3_TX_DMA_IRQHandler DMA1_Stream3_IRQn

#define UART3_TX_DMA_FLAG_TCIF DMA_FLAG_TCIF3

//#define UART3_RX_DMAy_Streamx DMA1_Stream1

//#define UART3_RX_DMA_Channel DMA_Channel_4

/************************************ ******************************/

然后进行管脚配置GPIO_Configuration();

#ifdef RT_USING_UART3

GPIO_InitStruct.GPIO_Mode=GPIO_Mode_AF;

GPIO_InitStruct.GPIO_OType=GPIO_OType_PP;

GPIO_InitStruct.GPIO_PuPd=GPIO_PuPd_UP;

GPIO_InitStruct.GPIO_Pin=UART3_GPIO_TX;

GPIO_InitStruct.GPIO_Speed=GPIO_Speed_50MHz;

GPIO_Init(UART3_GPIO,&GPIO_InitStruct);

GPIO_InitStruct.GPIO_Mode=GPIO_Mode_AF;

GPIO_InitStruct.GPIO_Pin=UART3_GPIO_RX;

GPIO_Init(UART3_GPIO,&GPIO_InitStruct);

GPIO_PinAFConfig(UART3_GPIO, UART3_TX_PinSource, GPIO_AF_USART3);

GPIO_PinAFConfig(UART3_GPIO, UART3_RX_PinSource, GPIO_AF_USART3);

#endif

/************************************ ******************************/

接着中断配置NVIC_Configuration();

#ifdef RT_USING_UART3

/* Enable the USART3 Interrupt */

NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

/* Enable the DMA1 Stream4 Interrupt */

NVIC_InitStructure.NVIC_IRQChannel = UART3_TX_DMA_IRQHandler;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

#endif

这里需要注意说明的是STM32F2系列和STM32F1系列的DMA配置有些不同，F1系列配置时要注意DMAy_Channelx,F2系列用了另外一个名字DMAy_Streamx

DMAy_Channelx,:        where y can be 1 or 2 to select the DMA and x can be 1 to 7 for DMA1 and 1 to 5 for DMA2 to select the DMA Channel.

DMAy_Streamx,:        where y can be 1 or 2 to select the DMA and x can be 0 to 7 to select the DMA Stream

关于STM32F207的DMA有篇博客写的比较详细，大家可以参考一下。

连接3

/************************************ ******************************/

然后配置DMADMA_Configuration();

DMA_InitTypeDef DMA_InitStructure;

DMA_InitStructure.DMA_Channel = UART3_TX_DMA_Channel;

DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; /* Specifies whether the Peripheral address register should be incremented or not */

DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; /* Specifies whether the memory address register should be incremented or not */

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_VeryHigh;

DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;

DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;

DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;

DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;

DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;

DMA_DeInit(UART3_TX_DMAy_Streamx);

DMA_InitStructure.DMA_PeripheralBaseAddr = USART3_DR_Base;

DMA_InitStructure.DMA_Memory0BaseAddr = (u32)0;

DMA_InitStructure.DMA_BufferSize = 1;

DMA_Init(UART3_TX_DMAy_Streamx,&DMA_InitStructure);

//        DMA_Cmd(UART3_TX_DMAy_Streamx, ENABLE);/* move to rt_serial_enable_dma() by RTT */

DMA_ITConfig(UART3_TX_DMAy_Streamx, DMA_IT_TC | DMA_IT_TE, ENABLE);

DMA_ClearFlag(UART3_TX_DMAy_Streamx, UART3_TX_DMA_FLAG_TCIF);

/************************************ ******************************/

最后进行UART的配置

#ifdef RT_USING_UART3

USART_DeInit(USART3);

USART_InitStructure.USART_BaudRate            = 19200;

USART_InitStructure.USART_WordLength          = USART_WordLength_8b;

USART_InitStructure.USART_StopBits            = USART_StopBits_1;

USART_InitStructure.USART_Parity            = USART_Parity_No ;

USART_InitStructure.USART_HardwareFlowContro=USART_HardwareFlowControl_None;

USART_InitStructure.USART_M = USART_Mode_Rx | USART_Mode_Tx;

USART_Init(USART3, &USART_InitStructure);

uart3_dma_tx.dma_channel= UART3_TX_DMAy_Streamx;

/* register uart3 */

rt_hw_serial_register(&uart3_device, "uart3",

RT_DEVICE_FLAG_RDWR|RT_DEVICE_FLAG_INT_RX|RT_DEVICE_FLAG_DMA_TX,&uart3);

/* Enable USART3 DMA Tx request */

USART_DMACmd(USART3, USART_DMAReq_Tx , ENABLE);

/* enable interrupt */

USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);

USART_ClearFlag(USART3,USART_FLAG_TXE);

#endif

uart3_dma_tx.dma_channel= UART3_TX_DMAy_Streamx;这条语句一定要当心，这里不是配置dma_channel，因为在seria.c中rt_serial_enable_dma()进行DMA的使能和失能

例如DMA_Cmd(dma_channel, ENABLE);

但是st的F2系列的库函数中DMA配置的是Stream，而不是channel

DMA_Cmd(DMA_Stream_TypeDef* DMAy_Streamx, FunctionalState NewState)

到这里UART3的初始化就OK了，再进入中断函数stm32f2xx_it.c配置

/*********************DMA中断******************************/

#define UART3_TX_DMAy_Streamx DMA1_Stream3

#define UART3_TX_DMA_IT_TCIF DMA_IT_TCIF3

#define UART3_TX_DMA_IT_TEIF DMA_IT_TCIF3

#define UART3_TX_DMA_FLAG_TCIF DMA_FLAG_TCIF3

#define UART3_TX_DMA_FLAG_TEIF DMA_FLAG_TCIF3

void DMA1_Stream3_IRQHandler(void)

{

#ifdef RT_USING_UART3

extern struct rt_device uart3_device;

extern void rt_hw_serial_dma_tx_isr(struct rt_device *device);

/* enter interrupt */

rt_interrupt_enter();

if(DMA_GetITStatus(UART3_TX_DMAy_Streamx,UART3_TX_DMA_IT_TCIF))

{

/* transmission complete, invoke serial dma tx isr */

rt_hw_serial_dma_tx_isr(&uart3_device);

}

/* clear DMA flag */

DMA_ClearFlag(UART3_TX_DMAy_Streamx,DMA_FLAG_TCIF3 | UART3_TX_DMA_FLAG_TEIF);

/* leave interrupt */

rt_interrupt_leave();

#endif

}

在中断函数中，大家一定要注意DMA_GetITStatus() 和 DMA_GetFLAGStatus(),不能混淆了，我就吃过亏。一旦弄错了，DMA中断程序不正常，就导致了DMA只能发送一次。

在APPTask.c中创建了一个任务，进行发送。

void usart_tx_thread_entry(void *p)

{

char tx_buf[]="hello pc!\r\n";

u8 datalen;

while(1)

{

datalen = strlen(tx_buf);

dev_uart3->write(dev_uart3,0,tx_buf,datalen);

rt_thread_delay(RT_TICK_PER_SECOND*2);

}

}

串口输出

因为我刚接触RTT系统，所以会有很多考虑不周全的方面，请大家指出，呵呵！2013.1.6

因为我不能发连接，所以文中提到连接地方到放到了附件pdf中

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