MSP430 Learning Notes 4-Two timers generate step single frequency tone

This program is used in the development board to generate sounds of different frequencies. The overall program is relatively simple, mainly using two timers. The code and my comments are as follows.

1. /********************************************************* 

2. Program function: Use fixed frequency square wave to drive buzzer, a total of 16 tones; 

3.           While emitting different tones, the LED lights up to indicate the 

4.           The number of the current tone (1~16) 

5. ---------------------------------------------------------- 

6. Dip switch setting: turn BUZZER to ON and the rest to OFF 

7. Test instructions: Listen to the tone change of the buzzer. At the same time, the LED also has corresponding indications 

8. **********************************************************/  

9. #include   

10.   

11. typedef unsigned char uchar;  

12.   

13. uchar step = 0xff;  

14.   

15. /****************************Main function****************************/  

16. void main( void )  

17. {  

18.     flying i;  

19.       

20.     WDTCTL = WDTPW + WDTHOLD;           //关狗  

21.      

22.     /*The following six lines of code close all IO ports*/  

23.     P1DIR = 0XFF;P1OUT = 0XFF;  

24.     P2DIR = 0XFF;P2OUT = 0XFF;  

25.     P3DIR = 0XFF;P3OUT = 0XFF;  

26.     P4DIR = 0XFF;P4OUT = 0XFF;  

27.     P5DIR = 0XFF;P5OUT = 0XFF;  

28.     P6DIR = 0XFF;P6OUT = 0XFF;  

29.     P6DIR |= BIT2;P6OUT |= BIT2; //Disable level conversion  

30.       

31.     /*------Select the system main clock as 8MHz-------*/  

32.     BCSCTL1 &= ~XT2OFF; //Turn on XT2 high frequency crystal oscillator  

33.     do  

34.     {  

35.         IFG1 &= ~OFIFG; // Clear crystal oscillator failure flag  

36.         //IFG1 is the interrupt register OFIFG is the crystal oscillator startup failure interrupt flag  

37.         for (i = 0xFF; i > 0; i--); //Wait for 8MHz crystal to start oscillating  

38.     }  

39.     while ((IFG1 & OFIFG)); //Does the crystal oscillator failure flag still exist?  

40.     //The above step is mainly to wait for the crystal oscillator to work normally  

41.     BCSCTL2 |= SELM_2 + SELS; //MCLK and SMCLK select high frequency crystal  

42.       

43.     TACCTL0 |= CCIE; //Enable compare interrupt  

44.     TACTL |= TASSEL_2 + ID_3 ; //Count clock selection SMLK=8MHz, 1/8 division is 1MHz  

45.       

46.     TBCCR0 = 4096*2 - 1; //cycle two seconds  

47.     //Time calculation: 32768/8*2+1 Note that a watch crystal is used  

48.     TBCCTL0 |= CCIE;  

49.     TBCTL |= TBSSEL_1 + ID_3 + MC_1;    //时钟源ACLK/8，up mode  

50.       

51.     P6DIR |= BIT7; //Buzzer corresponds to IO 6.7 and is set as output  

52.     P2DIR = 0xff; //Indicates the corresponding status  

53.     P2OUT = 0xff;  

54.       

55.     _UNITE();  

56.       

57.     LPM1;  

58. }  

59. /******************************************* 

60. Function name: Timer_A 

61. Function: interrupt service function of timer A, driven here 

62.           Buzzer sounds 

63. Parameters: None 

64. Return value: None 

65. ********************************************/  

66. #pragma vector=TIMERA0_VECTOR  

67. __interrupt void Timer_A (void)  

68. {  

69.   P6OUT ^= BIT7;                            // Toggle P6.7  

70. }  

71. /******************************************* 

72. Function name: Timer_B 

73. Function: Interrupt service function of timer B, change here 

74.           Buzzer sound frequency 

75. Parameters: None 

76. Return value: None 

77. ********************************************/  

78. #pragma vector=TIMERB0_VECTOR  

79. __interrupt void Timer_B (void)  

80. {  

81.     if(step == 0xff) //The initial value of step is 0xff,  

82.       TACTL |= MC_1; //TimerA needs to be set to up-counting mode. This can be set during initialization. I don't understand why it is placed here.     

83.     step++;  

84.     switch(step)  

85.     {    

86.     case    0:  TACCR0 = 5000;  P2OUT = ~1;   break;      // 100Hz  

87.     //P2OUT uses LED to display the corresponding value, just for demonstration, no practical significance  

88.     case    1:  TACCR0 = 2500;  P2OUT = ~2;   break;      // 200Hz  

89.     case    2:  TACCR0 = 1250;  P2OUT = ~3;   break;      // 400Hz  

90.     case    3:  TACCR0 = 625;   P2OUT = ~4;   break;      // 800Hz  

91.     case    4:  TACCR0 = 500;   P2OUT = ~5;   break;      // 1KHz  

92.     case    5:  TACCR0 = 250;   P2OUT = ~6;   break;      // 2KHz  

93.     case    6:  TACCR0 = 167;   P2OUT = ~7;   break;      // 3KHz  

94.     case    7:  TACCR0 = 125;   P2OUT = ~8;   break;      // 4KHz  

95.     case    8:  TACCR0 = 100;   P2OUT = ~9;   break;      // 5KHz  

96.     case    9:  TACCR0 = 83;    P2OUT = ~10;   break;      // 6KHz  

97.     case    10:  TACCR0 = 71;   P2OUT = ~11;   break;      // 7KHz  

98.     case    11:  TACCR0 = 63;   P2OUT = ~12;   break;      // 8KHz  

99.     case    12:  TACCR0 = 56;   P2OUT = ~13;   break;      // 9KHz  

100.     case    13:  TACCR0 = 50;   P2OUT = ~14;   break;      // 10KHz  

101.     case    14:  TACCR0 = 33;   P2OUT = ~15;   break;      // 15KHz  

102.     case    15:  TACCR0 = 25;   P2OUT = ~16;   break;      // 20KHz  

103.     case 16: step = 0xff; // Continue to add, the same effect as clearing, loop playback  

104.     }  

105. }