reactos/hal/halx86/generic/beep.c

/*
 * PROJECT:         ReactOS HAL
 * LICENSE:         BSD - See COPYING.ARM in the top level directory
 * FILE:            hal/halx86/generic/beep.c
 * PURPOSE:         Speaker support (beeping)
 * PROGRAMMERS:     ReactOS Portable Systems Group
 */

/* INCLUDES ******************************************************************/

#include <hal.h>
#define NDEBUG
#include <debug.h>

/* FUNCTIONS *****************************************************************/

/*
 * @implemented
 */
BOOLEAN
NTAPI
HalMakeBeep(IN ULONG Frequency)
{
    SYSTEM_CONTROL_PORT_B_REGISTER SystemControl;
    TIMER_CONTROL_PORT_REGISTER TimerControl;
    ULONG Divider;
    BOOLEAN Result = FALSE;

    //
    // Acquire CMOS Lock
    //
    HalpAcquireCmosSpinLock();

    //
    // Turn the timer off by disconnecting its output pin and speaker gate
    //
    SystemControl.Bits = __inbyte(SYSTEM_CONTROL_PORT_B);
    SystemControl.SpeakerDataEnable = FALSE;
    SystemControl.Timer2GateToSpeaker = FALSE;
    __outbyte(SYSTEM_CONTROL_PORT_B, SystemControl.Bits);

    //
    // Check if we have a frequency
    //
    if (Frequency)
    {
        //
        // Set the divider
        //
        Divider = PIT_FREQUENCY / Frequency;

        //
        // Check if it's too large
        //
        if (Divider <= 0x10000)
        {
            //
            // Program the PIT for binary mode
            //
            TimerControl.BcdMode = FALSE;

            //
            // Program the PIT to generate a square wave (Mode 3) on channel 2.
            // Channel 0 is used for the IRQ0 clock interval timer, and channel
            // 1 is used for DRAM refresh.
            //
            // Mode 2 gives much better accuracy, but generates an output signal
            // that drops to low for each input signal cycle at 0.8381 useconds.
            // This is too fast for the PC speaker to process and would result
            // in no sound being emitted.
            //
            // Mode 3 will generate a high pulse that is a bit longer and will
            // allow the PC speaker to notice. Additionally, take note that on
            // channel 2, when input goes low the counter will stop and output
            // will go to high.
            //
            TimerControl.OperatingMode = PitOperatingMode3;
            TimerControl.Channel = PitChannel2;

            //
            // Set the access mode that we'll use to program the reload value.
            //
            TimerControl.AccessMode = PitAccessModeLowHigh;

            //
            // Now write the programming bits
            //
            __outbyte(TIMER_CONTROL_PORT, TimerControl.Bits);

            //
            // Next we write the reload value for channel 2
            //
            __outbyte(TIMER_CHANNEL2_DATA_PORT, Divider & 0xFF);
            __outbyte(TIMER_CHANNEL2_DATA_PORT, (Divider >> 8) & 0xFF);

            //
            // Reconnect the speaker to the timer and re-enable the output pin
            //
            SystemControl.Bits = __inbyte(SYSTEM_CONTROL_PORT_B);
            SystemControl.SpeakerDataEnable = TRUE;
            SystemControl.Timer2GateToSpeaker = TRUE;
            __outbyte(SYSTEM_CONTROL_PORT_B, SystemControl.Bits);
            Result = TRUE;
        }
    }

    //
    // Release CMOS lock
    //
    HalpReleaseCmosSpinLock();

    //
    // Return success
    //
    return Result;
}