C64 SID programming in C

Test program sid.c:

/*
 
SID tone generator

*/
 
#include <stdio.h>
 
typedef unsigned char uint8_t;
typedef unsigned short uint16_t;
 
uint16_t g_freq[8] = {
    0x22cd,
    0x2710,
    0x2bd8,
    0x2e74,
    0x3424,
    0x3a87,
    0x41b2,
    0x459a
};
 
uint8_t* g_sidBase = (uint8_t*) 0xd400;
 
void setVolume(uint8_t volume)
{
    g_sidBase[24] = volume | (1 << 4);
}
 
void initSid()
{
    uint8_t i = 0;
    for (i = 0; i < 24; i++) g_sidBase[i] = 0;
    setVolume(15);
}
 
void setFrequency(uint8_t voice, uint16_t freqIndex)
{
    uint16_t freq = g_freq[freqIndex];
    g_sidBase[7 * voice] = freq & 0xff;
    g_sidBase[7 * voice + 1] = freq >> 8;
}
 
void setAdsr(uint8_t voice, uint8_t attack, uint8_t decay, uint8_t sustain, uint8_t release)
{
    g_sidBase[7 * voice + 5] = (attack << 4) | decay;
    g_sidBase[7 * voice + 6] = (sustain << 4) | release;
}
 
void startTriangle(uint8_t voice)
{
    g_sidBase[7 * voice + 4] = (1 << 4) | 1;
}
 
void stopTriangle(uint8_t voice)
{
    g_sidBase[7 * voice + 4] = 1 << 4;
}
 
void delay()
{
    long i;
    for (i = 0; i < 500; i++);
}
 
void startTone(uint8_t voice, uint8_t freqIndex)
{
    setFrequency(voice, freqIndex);
    setAdsr(voice, 2, 1, 15, 1);
    startTriangle(voice);
}
 
void stopTone(uint8_t voice)
{
    stopTriangle(voice);
}
 
void playOneTone(uint8_t freqIndex)
{
    startTone(0, freqIndex);
    delay();
    stopTone(0);
}
 
void playThreeTones(uint8_t freqIndex0, uint8_t freqIndex1, uint8_t freqIndex2)
{
    startTone(0, freqIndex0);
    startTone(1, freqIndex1);
    startTone(2, freqIndex2);
    delay();
    stopTone(0);
    stopTone(1);
    stopTone(2);
}
 
int main()
{
    initSid();
    g_sidBase[23] = 7;
    g_sidBase[22] = 10;
    while (1) {
        uint8_t i;
        for (i = 0; i < 8; i++) {
            playOneTone(i);
        }
        delay();
        
        playThreeTones(0, 2, 5);
        playThreeTones(2, 5, 7);
        playThreeTones(1, 2, 5);
        playThreeTones(0, 2, 5);
        playThreeTones(0, 2, 4);
        playThreeTones(0, 2, 5);
        delay();
    }
    return 0;
}

Compiled with cc65: sid.prg (compiled with "cl65 -O -t c64 sid.c -o sid.prg").

Testing in WinVICE:

"\Program Files\WinVICE-2.2-x64\x64.exe" sid.prg