From 2ce7e6a7a4b27c9896e66530f29dc110ceaf2d13 Mon Sep 17 00:00:00 2001
From: Arthur Lu <learthurgo@gmail.com>
Date: Wed, 1 Dec 2021 15:17:58 -0800
Subject: [PATCH] add wave genration functions

---
 src/generate_sine.m     | 15 +++++++++++++++
 src/generate_square.m   | 20 ++++++++++++++++++++
 src/generate_triangle.m | 19 +++++++++++++++++++
 src/play_wave.m         |  5 +++++
 src/plot_wave.m         |  8 ++++++++
 5 files changed, 67 insertions(+)
 create mode 100644 src/generate_sine.m
 create mode 100644 src/generate_square.m
 create mode 100644 src/generate_triangle.m
 create mode 100644 src/play_wave.m
 create mode 100644 src/plot_wave.m

diff --git a/src/generate_sine.m b/src/generate_sine.m
new file mode 100644
index 0000000..76c4a09
--- /dev/null
+++ b/src/generate_sine.m
@@ -0,0 +1,15 @@
+function x = generate_sine(amplitude, frequency, phase, fs, duration)
+%GENERATE_SINE:Arthur Lu returns a matrix of sampled sine wave, where the
+%phase shift is in number of periods
+    x = zeros(1, fs * duration);
+    A = amplitude;
+    f = frequency;
+    p = phase;
+    n = fs * duration;
+    dt = 1 / fs;
+    for i = 1:n
+        t = i * dt;
+        x(i) = A * sin(2 * pi * f * t - p);
+    end
+end
+
diff --git a/src/generate_square.m b/src/generate_square.m
new file mode 100644
index 0000000..bf3134e
--- /dev/null
+++ b/src/generate_square.m
@@ -0,0 +1,20 @@
+function x = generate_square(amplitude, frequency, phase, fs, duration, duty)
+%GENERATE_SINE:Arthur Lu returns a matrix of sampled sine wave, where the
+%phase shift is in number of periods
+    x = zeros(1, fs * duration);
+    A = amplitude;
+    f = frequency;
+    p = phase;
+    n = fs * duration;
+    dt = 1 / fs;
+    for i = 1:n
+        t = i * dt;
+        st = mod(f * t - p, 1);
+        if(st < duty)
+            x(i) = A;
+        else
+            x(i) = -A;
+        end
+    end
+end
+
diff --git a/src/generate_triangle.m b/src/generate_triangle.m
new file mode 100644
index 0000000..94b78ad
--- /dev/null
+++ b/src/generate_triangle.m
@@ -0,0 +1,19 @@
+function x = generate_triangle(amplitude, frequency, phase, fs, duration, duty)
+%GENERATE_SINE:Arthur Lu returns a matrix of sampled sine wave, where the
+%phase shift is in number of periods
+    x = zeros(1, fs * duration);
+    A = amplitude;
+    f = frequency;
+    p = phase;
+    n = fs * duration;
+    dt = 1 / fs;
+    for i = 1:n
+        t = i * dt;
+        st = mod(f * t - p, 1);
+        if(st < duty)
+            x(i) = A*(1/duty * st - 0.5);
+        else
+            x(i) = A*(-(1/(1-duty))*st + (duty/(1-duty)) + 1 - 0.5);
+        end
+    end
+end
\ No newline at end of file
diff --git a/src/play_wave.m b/src/play_wave.m
new file mode 100644
index 0000000..56d4c26
--- /dev/null
+++ b/src/play_wave.m
@@ -0,0 +1,5 @@
+function play_wave(wave, fs)
+%PLAY_WAVE:Arthur Lu plays a wave as sound
+    sound(wave, fs)
+end
+
diff --git a/src/plot_wave.m b/src/plot_wave.m
new file mode 100644
index 0000000..b28a588
--- /dev/null
+++ b/src/plot_wave.m
@@ -0,0 +1,8 @@
+function plot_wave(waveform, fs, duration)
+%PLOT_WAVE:Arthur Lu plots a waveform
+    x = linspace(0, duration, fs * duration);
+    plot(x, waveform);
+    xlabel("time");
+    ylabel("amplitude");
+end
+