Creating square, sawtooth and triangle wave in Objective-C - ios

Question

I am trying to generate different wave shapes for a simple wavetable synth iOS app I am working on. This is how I am generating the sine wave:
if (waveType == 1) // sine wave
{
//NSLog(#"sine in AU");
for (int i=0;i<n;i++)
{
float x = 0.0; // default to silence
if (toneCount > 0) // or create a sinewave
{
x = testVolume * sinf(ph);
ph = ph + dp;
if (ph > M_PI) { ph -= 2.0 * M_PI; } // sine wave
toneCount -= 1; // decrement tone length counter
}
if (ptrLeft != NULL){
ptrLeft[ i] = x;
}
if (ptrRight != NULL) {
ptrRight[i] = x;
}
}
}
For a square wave I was assuming this would work but it hasn't:
if (ph > M_PI) {
ph -= 2.0 * M_PI;
ph >= 0 ? 1.0 : -1.0;
}
How would I go about creating sawtooth and triangles waves and where is the square wave going wrong?
Thanks, I'm new to iOS programming and love working with audio.

Answer 1

For starters think about your line
if (ph > M_PI) { ph -= 2.0 * M_PI; } // sine wave
ph is your input into your sin function which is some value in radians ... be aware that sin function will automatically handle values greater than 2 * PI it will simply wrap it around so no need to manage your ph variable other then simply incrementing it
Regarding your square wave ... keep in mind your output has only two values low or high ... do not drive the toggle between low/high by value of the curve
if (ph > M_PI) {
ph -= 2.0 * M_PI;
ph >= 0 ? 1.0 : -1.0;
}
keep in mind that as you increment your outer loop i you are incrementing ph which you are using to determine where you are in your PI cycles which is OK however that same ph then cannot also be input to sin(ph) as well ... something else must get fed into sin() or else something else maintains your sample position in your PI cycle ... you are mistakenly conflating two responsibilities into a single variable
In above if code block think about when you must perform the toggle from low to high or back from high to low ... does it happen at M_PI ? how many such toggles happen per cycle ? when ? perhaps you need an additional if test to determine when to perform that toggle ... in your sin curve algorithm you are already managing ph must you handle square wave ph differently or leave ph logic the same ?