STM32F10x 学习笔记8（USART实现串口通讯 DMA 方式）

1. te=9600;
2. USART_InitStructure.USART_WordLength=USART_WordLength_8b;
3. USART_InitStructure.USART_StopBits=USART_StopBits_1;
4. USART_InitStructure.USART_Parity=USART_Parity_No;
5. USART_InitStructure.USART_HardwareFlowControl=USART_HardwareFlowControl_None;
6. USART_InitStructure.USART_Mode=USART_Mode_Rx|USART_Mode_Tx;
7. USART_Init(USART2,&USART_InitStructure);
9. USART_Cmd(USART2,ENABLE);
10. }
12. voidUART2_TX_DMA_Init(uint8_t*p_str,uint16_tcnt)
13. {
14. //DMA_InitTypeDefDMA_InitStructure;
15. //DMA_InitStructure.DMA_PeripheralBaseAddr=(uint32_t)&(USART2->DR);
16. //DMA_InitStructure.DMA_MemoryBaseAddr=(uint32_t)str;
17. //DMA_InitStructure.DMA_DIR=DMA_DIR_PeripheralDST;
18. //DMA_InitStructure.DMA_BufferSize=14;
19. //DMA_InitStructure.DMA_PeripheralInc=DMA_PeripheralInc_Disable;
20. //DMA_InitStructure.DMA_MemoryInc=DMA_MemoryInc_Enable;
21. //DMA_InitStructure.DMA_PeripheralDataSize=DMA_PeripheralDataSize_Byte;
22. //DMA_InitStructure.DMA_MemoryDataSize=DMA_MemoryDataSize_Byte;
23. //DMA_InitStructure.DMA_Mode=DMA_Mode_Normal;
24. //DMA_InitStructure.DMA_Priority=DMA_Priority_Low;
25. //DMA_InitStructure.DMA_M2M=DMA_M2M_Disable;
27. RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1,ENABLE);
28. //DMA_Init(DMA1_Channel7,&DMA_InitStructure);
30. DMA1_Channel7->CPAR=(uint32_t)&(USART2->DR);
31. DMA1_Channel7->CMAR=(uint32_t)p_str;
32. DMA1_Channel7->CNDTR=cnt;
33. DMA1_Channel7->CCR=DMA_DIR_PeripheralDST|DMA_Priority_Low|
34. DMA_Mode_Normal|DMA_PeripheralInc_Disable|
35. DMA_MemoryInc_Enable|DMA_PeripheralDataSize_Byte|
36. DMA_MemoryDataSize_Byte|DMA_M2M_Disable;
37. }
39. uint8_tstr[]="HelloWorld!!!";
40. voidTaskStart(void*pdata)
41. {
42. SysTick_Config(SystemCoreClock/10);
43. USART2_Init();
44. UART2_TX_DMA_Init(str,14);
45. for(;;)
46. {
47. LED_Spark();
48. //DMA_Cmd(DMA1_Channel7,DISABLE);
49. DMA1_Channel7->CCR&=(uint16_t)(~DMA_CCR1_EN);
50. //DMA_Init(DMA1_Channel7,&DMA_InitStructure);
51. DMA1_Channel7->CNDTR=14;
52. //DMA_Cmd(DMA1_Channel7,ENABLE);
53. DMA1_Channel7->CCR|=DMA_CCR1_EN;
54. //USART_DMACmd(USART2,USART_DMAReq_Tx,ENABLE);
55. OSTimeDly(10);
56. }
57. }
59. intmain(void)
60. {
61. SystemInit();
62. LED_Init();
63. OSInit();
64. OSTaskCreate(TaskStart,(void*)0,&(TaskStartStk[TASK_STK_SIZE-1]),1);
65. OSStart();
66. for(;;)
67. {
69. }
70. }

下面再说说如何在DMA传输完成之后产生中断。当传输一半的数据后，半传输标志(HTIF)被置1，当设置了允许半传输中断位(HTIE)时，将产生一个中断请求。在数据传输结束后，传输完成标志(TCIF)被置1，当设置了允许传输完成中断位(TCIE)时，将产生一个中断请求。

DMA的CCR寄存器中有1位TCIE(Transfercompleteinterruptenable)

该位由软件设置和清除。

0：禁止TC中断

1：允许TC中断

所以为了使用DMA中断，我们需要下面的代码：

1. DMA1_Channel7->CCR|=DMA_IT_TC;//Transfercompleteinterruptenable

1. NVIC_InitStructure.NVIC_IRQChannel=DMA1_Channel7_IRQn;
2. NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=5;
3. NVIC_InitStructure.NVIC_IRQChannelSubPriority=0;
4. NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;
5. NVIC_Init(&NVIC_InitStructure);

下面还是给个简单的示例程序，示例程序中还用到了uCOS的信号量，中断处理函数通过信号量通知Task完成了DMA传输：

1. #include"stm32f10x.h"
2. #include"uart.h"
3. #include"led.h"
4. #include"COMMRTOS.H"
5. #include"ucos_ii.h"
7. #defineTASK_STK_SIZE128
8. OS_STKTaskStartStk[TASK_STK_SIZE];
11. voidUSART2_Init(void)
12. {
13. GPIO_InitTypeDefGPIO_InitStructure;
14. USART_InitTypeDefUSART_InitStructure;
15. NVIC_InitTypeDefNVIC_InitStructure;
17. RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD|RCC_APB2Periph_AFIO,ENABLE);
19. /*ConfigureUSARTTxasalternatefunctionpush-pull*/
20. GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF_PP;
21. GPIO_InitStructure.GPIO_Pin=GPIO_Pin_5;
22. GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
23. GPIO_Init(GPIOD,&GPIO_InitStructure);
25. /*ConfigureUSARTRxasinputfloating*/
26. GPIO_InitStructure.GPIO_Mode=GPIO_Mode_IN_FLOATING;
27. GPIO_InitStructure.GPIO_Pin=GPIO_Pin_6;
28. GPIO_Init(GPIOD,&GPIO_InitStructure);
30. GPIO_PinRemapConfig(GPIO_Remap_USART2,ENABLE);
31. RCC_APB1PeriphClockCmd(RCC_APB1Periph_USAR