Chris Taylor / Mbed 2 deprecated RETRO-CaveDweller Featured

Platform game written for the GHI/OutrageousCircuits RETRO game device. Navigate the caves collecting all the pickups and avoiding the creatures and haunted mine carts that patrol the caves. Oh and remember to watch out for the poisonous plants... This game demonstrates the ability to have multiple animated sprites where the sprites can overlap the background environment. See how the player moves past the fence and climbs the wall in the 3rd screen.

Dependencies:   mbed

OneBitSound/SoundChannel.cpp

Committer:
taylorza
Date:
2015-02-16
Revision:
16:f9227904afc4
Parent:
13:0900880bde68

File content as of revision 16:f9227904afc4:

#include "mbed.h"
#include "Fix16.h"
#include "SoundBlock.h"
#include "SoundChannel.h"

SoundChannel::SoundChannel() :
    _state(4)
{
}

void SoundChannel::play(const SoundBlock soundBlocks[], int count)
{
    _soundBlocks = soundBlocks;
    _count = count;    
    _index = 0;   
    _state = 0;   
}

bool SoundChannel::update(bool &pinState)
{
    switch(_state)
    {
        case 0 :
            startSoundBlock();
            break;
        
        case 3 : // Stop sound
            pinState = _pinState = false;
            _state = 4;
            return true;
        
        case 4 : // No sound
            return false;
    }

    if (updateCounters())
    {
        switch(_currentSoundBlock.getToneType())
        {
            case SoundBlock::Tone  : updateTone(); pinState = _pinState; return true;
            case SoundBlock::Noise : updateNoise(); pinState = _pinState; return true;
            case SoundBlock::Pause : return false;
        }
    }
    
    return false;
}

void SoundChannel::updateTone()
{
    switch(_state)
    {
        case 1: // High
        {
            _pinState = true;
            _pitchHighCounter -= fix16_one;
            if (_pitchHighCounter <= 0)
            {            
                _pinState = false;
                _pitchHighCounter += _basePitchHighCount;
                _state = 2;
            }
        }
        break;
            
        case 2: // Low
        {
            _pinState = false;
            _pitchLowCounter -= fix16_one;
            if (_pitchLowCounter <= 0)
            {
                _pinState = true;
                _pitchLowCounter += _basePitchLowCount;
                _state = 1;
            }
        }
        break;
    }    
}

void SoundChannel::updateNoise()
{
    switch(_state)
    {
        case 1: // High/Low        
        {   
            _pitchHighCounter -= fix16_one;
            if (_pitchHighCounter <= 0)
            {            
                _pinState = (SoundChannel::lfsr_rand() & 1) == 1;
                _pitchHighCounter += _basePitchHighCount;                
            }
        }
        break;
    }    
}

void SoundChannel::startSoundBlock()
{
    _currentSoundBlock = _soundBlocks[_index];
            
    _stepCounter = _currentSoundBlock.getStepCount();
    _stepDurationCounter = _currentSoundBlock.getStepDuration();
    _pitchOffset = 0;
    _dutyOffset = 0;
    
    updateAudioCounters();
    _pitchHighCounter = _basePitchHighCount;
    _pitchLowCounter = _basePitchLowCount;
    
    _state = 1;
}

bool SoundChannel::updateCounters()
{
    --_stepDurationCounter;
    if (_stepDurationCounter == 0)
    {    
        --_stepCounter;
        if (_stepCounter == 0)
        {                                
            ++_index;
            if (_index == _count)
            {                    
                _state = 3;
                return false;
            }
            else
            {
                _state = 0;
            }
        }                        
        else
        {  
            fix16_t pitchSlide = _currentSoundBlock.getPitchSlide();
            int8_t dutySlide = _currentSoundBlock.getDutySlide();
            if ( pitchSlide != 0 || dutySlide != 0)
            {
                _pitchOffset += pitchSlide;
                _dutyOffset += dutySlide;
                updateAudioCounters();
            }
        
            _stepDurationCounter = _currentSoundBlock.getStepDuration();
        }
    }
    return true;
}

void SoundChannel::updateAudioCounters()
{
    fix16_t pitch = _currentSoundBlock.getPitch(_pitchOffset);
    if (pitch == 0) pitch = fix16_one;
    
    if (_currentSoundBlock.getToneType() == SoundBlock::Noise)
        pitch = fix16_div(pitch, fix16_100);
        
    _basePitchHighCount = fix16_mul(pitch, _currentSoundBlock.getDuty(_dutyOffset) * 0x100);
    _basePitchLowCount = pitch - _basePitchHighCount;    
}

uint16_t SoundChannel::lfsr_rand()
{
    static uint16_t lfsr = 0xACE1u;
    lfsr = (lfsr >> 1) ^ (-(lfsr & 1u) & 0xB400u);
    return lfsr;
}