source: orbit/octave/GenerateAudioCommand/halfSineGenDirect.m @ cb3655b

function wave = halfSineGenDirect(dir,halfPeriod_in_samples,zero,amp,sps) 

% dir: 'u' means UP, 'd' means down.
% halfPeriod: half period of sine signal[us].
% zero: zero level of cosine signal.
% amp: amplitude of cosine signal, in percentage. 

halfPeriod=halfPeriod_in_samples/sps;

bps = 16;       % bits per sample
%sps = 960000;     % sample rate [samples/s]
period = halfPeriod*2;   %period of [s]
freq = floor(sps/(halfPeriod_in_samples*2));       % frequency of the tone [Hz]

%linspace is an octave function that generates a sequence with certain step.
time = linspace(1/sps, halfPeriod, halfPeriod_in_samples);
if (dir== 'u') 
        wave = sin(time*2*pi*freq)'.*amp+zero;%'u' indicates above zero line
elseif (dir=='d')
        wave = sin((time+halfPeriod)*2*pi*freq)'.*amp+zero;%'d' indicates below zero line
endif

%wavwrite(wave, sps, bps, 'audio.wav');