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Asked: 2026-06-13T20:17:14+00:00

I have the c code for the micro-controller with buzzer. It works, but I

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I have the c code for the micro-controller with buzzer. It works, but I wonder how it works.
In wh.h/.cpp I have the function:

void setBuzzer(tBool on)
{
  if (TRUE == on)
    IOCLR = BUZZER_PIN;
  else
    IOSET = BUZZER_PIN;
}

That can enable and disable the buzzer. I don’t know what it really makes and what BUZZER_PIN, IOCLR and IOSET are?

The BUZZER_PIN occurs only once more in the code, in:

void immediateIoInit(void)
{
  tU8 initCommand[] = {0x12, 0x97, 0x80, 0x00, 0x40, 0x00, 0x14, 0x00, 0x00};
  //                                                         04 = LCD_RST# low
  //                                                         10 = BT_RST# low

  //make all key signals as inputs
  IODIR &= ~(KEYPIN_CENTER | KEYPIN_UP | KEYPIN_DOWN | KEYPIN_LEFT | KEYPIN_RIGHT);

  IODIR |= BUZZER_PIN;
  IOSET  = BUZZER_PIN;

  IODIR |= BACKLIGHT_PIN;
  IOSET  = BACKLIGHT_PIN;

It looks strange to me, because the IOSET value is changing just after setting it to BUZZER_PIN. So, what it can that way does?

One more question: can I do something more with buzzer? E.g. change to volume? Of course, the duration of sound can be adjusted with setBuzzer(1) than pause(time) and setBuzzer(0).

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1 Answer

  1. Editorial Team

    Somewhere you will find an include file that contains the #define for IOSET IOCLR etc.

    Usually, they map to GPIO register addresses, eg:

    #define FIO0DIR (*(volatile unsigned long *)0x3FFFC000)

    IOSET is usually a writeable address that is hardware-capable of setting to 1 all bits written to it that are 1, while leaving the remainder of the GPIO bits in their previous state. This eliminates the need for a read/modify/write operation and so is much more interrupt/thread friendly. It normally has a similar ‘IOCLR’ partner that can clear the bits on the GPIO port that are set in its argument without affecting the state of others.

    The port register itself is probabaly called’ IOPIN’, or something like that. Modifying one or subsets of bits directly using IOPIN requires a read/modify/write 🙁

    It appears that the buzzer is connected to one GPIO pin, so you can only turn it on and off – no finer control is possible.

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