sound.c

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/*****************************************************************************
 * ugBASIC - an isomorphic BASIC language compiler for retrocomputers        *
 *****************************************************************************
 * Copyright 2021-2026 Marco Spedaletti (asimov@mclink.it)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *----------------------------------------------------------------------------
 * Concesso in licenza secondo i termini della Licenza Apache, versione 2.0
 * (la "Licenza"); è proibito usare questo file se non in conformità alla
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 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Se non richiesto dalla legislazione vigente o concordato per iscritto,
 * il software distribuito nei termini della Licenza è distribuito
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/****************************************************************************
 * INCLUDE SECTION 
 ****************************************************************************/
 
#include "../../ugbc.h"
 
/****************************************************************************
 * CODE SECTION 
 ****************************************************************************/

/* <usermanual>
@keyword SOUND
@target cpc
</usermanual> */
void sound( Environment * _environment, int _freq, int _delay, int _channels ) {
 
    //Registers 0 and 1 operate together to form channel A's final pitch. The eight least significant bits are sent
    //to register 0 and the four most significant bits are sent to register 1. The output frequency is equal to the
    //IC's incoming clock frequency divided by 16 and then further divided by the number written to the course and
    //fine pitch registers, so the higher the number written to these, the lower the pitch. For example, if a 
    //frequency of 1KHz was required and the IC's clock frequency was 1MHz, a total division rate of 1000 would
    //be needed. The sound generator itself divides by 16 so the course and fine pitch registers must provide a 
    //further division by 62.5 (due to the fact that 1000/16 is 62.5). A division rate of 62 or 63 will be
    //accurate enough, since the registers can only store whole numbers. Therefore, 62 or 63 would be written
    //to register 0 and 0 would be written to register 1.
 
    int chipsetFrequency = ( 4000000 / _freq ) / 16;
 
    ay8910_start( _environment, ( _channels & 0x07 ) );
    ay8910_set_frequency( _environment, _channels, chipsetFrequency );
    if ( _delay ) {
        ay8910_set_duration( _environment, _channels, _delay / 20 /* approx! */ );
        ay8910_wait_duration( _environment, _channels );
    }
 
}

void sound_vars( Environment * _environment, char * _freq, char * _delay, char * _channels ) {
 
    Variable * freq = variable_retrieve_or_define( _environment, _freq, VT_WORD, 440 );
 
    Variable * cpuFrequency = variable_temporary( _environment, VT_DWORD, "(chipsetFrequency)" );
    variable_store( _environment, cpuFrequency->name, 4000000 );
    Variable * sixteen = variable_temporary( _environment, VT_WORD, "(16)" );
    variable_store( _environment, sixteen->name, 16 );
    
    Variable * chipsetFrequency = variable_div( _environment, 
                            variable_div( _environment,
                                cpuFrequency->name,
                                freq->name,
                                NULL
                            )->name,
                            sixteen->name,
                            NULL
                            );
 
    if ( _channels ) {
        Variable * channels = variable_retrieve_or_define( _environment, _channels, VT_WORD, 0x07 );
        ay8910_start_var( _environment, channels->realName );
        ay8910_set_frequency_vars( _environment, channels->realName, chipsetFrequency->realName );
        if ( _delay ) {
            Variable * delay = variable_retrieve_or_define( _environment, _delay, VT_WORD, 0 );
            Variable * durationInTicks = variable_div_const( _environment, delay->name, 20, NULL );
            ay8910_set_duration_vars( _environment, channels->realName, durationInTicks->realName );
            ay8910_wait_duration_vars( _environment, channels->realName );
        }        
    } else {
        ay8910_start_var( _environment, NULL );
        ay8910_set_frequency_vars( _environment, NULL, chipsetFrequency->realName );
        if ( _delay ) {
            Variable * delay = variable_retrieve_or_define( _environment, _delay, VT_WORD, 0 );
            Variable * durationInTicks = variable_div_const( _environment, delay->name, 20, NULL );
            ay8910_set_duration_vars( _environment, NULL, durationInTicks->realName );
            ay8910_wait_duration_vars( _environment, NULL );
        }        
    }
 
}