Various Applications of Buzzers in Microcontrollers

In general microcontroller textbooks, there are simple instructions on how to use buzzers. Here we will explain in detail how to write buzzers for different buzzers and different chips.

However, when developing the project, I found that the use of the buzzer in the textbook had great limitations.

In the textbooks, the length of the buzzer is controlled by a busy loop such as delay. However, in reality, this function not only wastes a lot of CPU resources, but also delays the running of other functions. If there are some time-related functions, it will cause time confusion.

In addition, during the buzzer sounding, no operations other than interrupts can be performed. Strictly speaking, except for the infinite loop of the main function, any other busy loop that idles the CPU must be used with caution and the time cannot be too long. Generally speaking, busy loops at the millisecond level are already intolerable.

In addition, this writing method cannot flexibly configure advanced functions such as long or short beeps, and how many times the beeps occur at a certain interval.

However, after checking, I found that turning the buzzer on and off are two different processes.

Therefore, I implemented the buzzer on/off functions and other related functions.

The function of the buzzer on function is to turn on the buzzer, set the time (long beep, short beep, medium beep), and set the number of times.

The function of the buzzer off function is to query the setting value of the on function to decide when to turn off the buzzer, when to turn on the buzzer again, and when to stop turning on the buzzer.

Local global variables control the number of times, and timer global variables control the time.

From the above description, it can be determined that the opening function can be used at will, while the closing function must be looped in the main function to query the setting value.

The following is an example of a function.

1. Necessary initialization

///////////////////Buzzer duration variable declaration//////////////////////

typedef enum //Open time

{

  BEEP_SHORT = SEC_01, //100ms

  BEEP_MIDDLE = SEC_03, //300ms

  BEEP_LONG = SEC_04 //400ms

} BEEP_LAST;

typedef enum //Close interval

{

BEEP_FAST = SEC_03,

BEEP_SLOW = SEC_05

} BEEP_SHUT;

static uint8_t tmp_beep_cnt; //Buzzer count temporary storage

static BEEP_LAST tmp_beep_on; //Buzzer turns on temporary storage

static BEEP_SHUT tmp_beep_period; //temporary storage of buzzer period

2. Buzzer on

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

/* Function: buzzer sounds

 * describe:

 * Parameters: duration of opening, duration of closing (one ring is optional), number of rings (>0)

 * return:

 * Note: The number cannot be written as 0 */

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

void beep_on(BEEP_LAST last, BEEP_SHUT off, uint8_t times)

{

BEEP_CSR |=1<<5; //Turn on the buzzer

freq.beep_on = last; //beep continues

freq.beep_period = last + off; //One on and off cycle

tmp_beep_on = last;

tmp_beep_period = last + off;

if(times > 0)

tmp_beep_cnt = times - 1;

else

tmp_beep_cnt = 0;

}

3. Buzzer off

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

/* Function: turn off the buzzer

 * Description: Detection time flag, turn it off when it is 0, and reduce the number by 1

 * Parameters:

 * return:

 * Note: This is inside the main loop */

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

void beep_off(void)

{

if (freq.beep_on == 0) //If the duration is up, turn off

{

BEEP_CSR &=~(1<<5); //Close

if (tmp_beep_cnt) //The buzzer is turned off, but the count is still there, wait for the conditions to be met to turn it back on

{

if (freq.beep_period == 0) //The buzzer period has expired

{

BEEP_CSR |=1<<5; //Turn on the buzzer

freq.beep_on = tmp_beep_on; //Assign the last duration

freq.beep_off = tmp_beep_period; //Re-count the buzzer period

s_beep_cnt--; //Number of times minus 1

}

}

}

}

Fourth, timer processing, interrupt once every 10ms.

/*Buzzer related timing*/

if (freq.beep_on)

freq.beep_on--; // duration of buzzer on

if(freq.beep_period)

freq.beep_period--; //Buzzer period