el_supremo
Well-known member
I changed the way that AudioSynthWaveform works. I've written some (small) documentation files for the classes I wrote or modified. This is the one for AudioSynthWaveform:
Code:
synth_waveform 140404
This synthesizes a waveform of the specified type with a given amplitude
and frequency. There are currently four types of waveform:
#define TONE_TYPE_SINE 0
#define TONE_TYPE_SAWTOOTH 1
#define TONE_TYPE_SQUARE 2
#define TONE_TYPE_TRIANGLE 3
Sine wave generation uses the arm library's arm_sin_q15 function. This function uses
a table lookup and cubic interpolation.
The other three waveforms are generated directly without using table lookup.
boolean begin(float t_amp,float t_freq,short t_type)
This starts generation of a waveform of given type, amplitude and frequency
Example: begin(0.8,440.0,TONE_TYPE_SINE)
void set_ramp_length(int16_t r_length)
When a tone starts, or ends, playing it can generate an audible "thump" which can
be very distracting, especially when playing musical notes. This function specifies
a "ramp" length (in number of samples) and the beginning of the generated waveform
will be ramped up in volume from zero to t_amp over the course of r_length samples.
When the tone is switched off, by changing its volume to zero, instead of ending
abruptly it will be ramped down to zero over the next r_length samples.
For example, if r_length is 44, the beginning and end of the wave will have a ramp
of approximately one millisecond.
void frequency(int t_freq)
Changes the frequency of the wave to the specified t_freq. This is done in a phase-
continuous manner which should allow generation of audio frequency shift keying and
other effects requiring a changing frequency.
void amplitude(float n)
Changes the amplitude to 'n'. If 'n' is zero the wave is turned off and any further
audio output will be zero.Pete
