STM32+Keil 如何使用printf函数？

那么只能通过程序向硬件串口发数据了，这样调用的时候用自定义的函数即可，也很方便，例如：

void send_char_to_usart(unsigned char c){}

但是可否直接使用printf函数呢？毕竟人家都做好了，我们给他定一个打印输出的接口就可以了，答案是肯定的，看ST的官方源码：

1. /**
2. ******************************************************************************
3. *@fileLib_DEBUG/Lib_DEBUG_Example/main.c
4. *@authorMCDApplicationTeam
5. *@versionV1.1.1
6. *@date13-April-2012
7. *@briefMainprogrambody
8. ******************************************************************************
9. *@attention
10. *
11. *
    COPYRIGHT2012STMicroelectronics

12. *
13. *LicensedunderMCD-STLibertySWLicenseAgreementV2,(the"License");
14. *YoumaynotusethisfileexceptincompliancewiththeLicense.
15. *YoumayobtainacopyoftheLicenseat:
16. *
17. *http://www.st.com/software_license_agreement_liberty_v2
18. *
19. *Unlessrequiredbyapplicablelaworagreedtoinwriting,software
20. *distributedundertheLicenseisdistributedonan"ASIS"BASIS,
21. *WITHOUTWARRANTIESORCONDITIONSOFANYKIND,eitherexpressorimplied.
22. *SeetheLicenseforthespecificlanguagegoverningpermissionsand
23. *limitationsundertheLicense.
24. *
25. ******************************************************************************
26. */
28. /*Includes------------------------------------------------------------------*/
29. #include"stm32l1xx.h"
30. #include"stm32l1xx_ip_dbg.h"
31. #include
33. #ifdefUSE_STM32L152D_EVAL
34. #include"stm32l152d_eval.h"
35. #else
36. #include"stm32l152_eval.h"
37. #endif
40. /**@addtogroupSTM32L1xx_StdPeriph_Examples
41. *@{
42. */
44. /**@addtogroupLib_DEBUG_Example
45. *@{
46. */
48. /*Privatetypedef-----------------------------------------------------------*/
49. /*Privatedefine------------------------------------------------------------*/
50. /*Privatemacro-------------------------------------------------------------*/
51. /*Privatevariables---------------------------------------------------------*/
52. USART_InitTypeDefUSART_InitStructure;
54. /*Privatefunctionprototypes-----------------------------------------------*/
55. #ifdef__GNUC__
56. /*WithGCC/RAISONANCE,smallprintf(optionLDLinker->Libraries->Smallprintf
57. settoYes)calls__io_putchar()*/
58. #definePUTCHAR_PROTOTYPEint__io_putchar(intch)
59. #else
60. #definePUTCHAR_PROTOTYPEintfputc(intch,FILE*f)
61. #endif/*__GNUC__*/
63. /*Privatefunctions---------------------------------------------------------*/
65. /**
66. *@briefMainprogram
67. *@paramNone
68. *@retvalNone
69. */
70. intmain(void)
71. {
72. /*!
73. thisisdonethroughSystemInit()functionwhichiscalledfromstartup
74. file(startup_stm32l1xx_xx.s)beforetobranchtoapplicationmain.
75. ToreconfigurethedefaultsettingofSystemInit()function,referto
76. system_stm32l1xx.cfile
77. */
79. GPIO_InitTypeDefGPIOA_InitStructure;
81. /*USARTxconfiguredasfollow:
82. -BaudRate=115200baud
83. -WordLength=8Bits
84. -OneStopBit
85. -Noparity
86. -Hardwareflowcontroldisabled(RTSandCTSsignals)
87. -Receiveandtransmitenabled
88. */
89. USART_InitStructure.USART_BaudRate=115200;
90. USART_InitStructure.USART_WordLength=USART_WordLength_8b;
91. USART_InitStructure.USART_StopBits=USART_StopBits_1;
92. USART_InitStructure.USART_Parity=USART_Parity_No;
93. USART_InitStructure.USART_HardwareFlowControl=USART_HardwareFlowControl_None;
94. USART_InitStructure.USART_Mode=USART_Mode_Rx|USART_Mode_Tx;
96. STM_EVAL_COMInit(COM1,&USART_InitStructure);
98. /*Initializeallperipheralspointers*/
99. IP_Debug();
101. printf("\r\nSTM32l1xxFirmwareLibrarycompiledwithFULLASSERTfunction...\n\r");
102. printf("...Run-timecheckingenabled\n\r");
104. /*Simulatewrongparameterpassedtolibraryfunction---------------------*/
105. /*ToenableSPI1clock,RCC_APB2PeriphClockCmdfunctionmustbeusedand
106. notRCC_APB1PeriphClockCmd*/
107. RCC_APB1PeriphClockCmd(RCC_APB2Periph_SPI1,ENABLE);
109. /*SomememberofGPIOA_InitStructurestructurearenotinitialized*/
110. GPIOA_InitStructure.GPIO_Pin=GPIO_Pin_6;
111. GPIOA_InitStructure.GPIO_Mode=GPIO_Mode_OUT;
112. /*GPIOA_InitStruc