From 6395d1d18b2fe0ece82f3b82c35648b0419378c2 Mon Sep 17 00:00:00 2001
From: Clyne Sullivan <clyne@bitgloo.com>
Date: Tue, 24 Nov 2020 10:17:52 -0500
Subject: oversample for lower rates; add iir templates

---
 gui/templates/6_iir_test.cpp | 13 +++++++++++++
 gui/templates/7_iir_echo.cpp | 22 ++++++++++++++++++++++
 2 files changed, 35 insertions(+)
 create mode 100644 gui/templates/6_iir_test.cpp
 create mode 100644 gui/templates/7_iir_echo.cpp

(limited to 'gui/templates')

diff --git a/gui/templates/6_iir_test.cpp b/gui/templates/6_iir_test.cpp
new file mode 100644
index 0000000..cdb4ab3
--- /dev/null
+++ b/gui/templates/6_iir_test.cpp
@@ -0,0 +1,13 @@
+adcsample_t *process_data(adcsample_t *samples, unsigned int size)
+{
+	constexpr float alpha = 0.7;
+
+	static adcsample_t prev = 2048;
+
+	samples[0] = (1 - alpha) * samples[0] + alpha * prev;
+	for (unsigned int i = 1; i < size; i++)
+		samples[i] = (1 - alpha) * samples[i] + alpha * samples[i - 1];
+	prev = samples[size - 1];
+
+	return samples;
+}
diff --git a/gui/templates/7_iir_echo.cpp b/gui/templates/7_iir_echo.cpp
new file mode 100644
index 0000000..8e93b35
--- /dev/null
+++ b/gui/templates/7_iir_echo.cpp
@@ -0,0 +1,22 @@
+adcsample_t *process_data(adcsample_t *samples, unsigned int size)
+{
+	constexpr float alpha = 0.75;
+	constexpr unsigned int D = 100;
+
+	static adcsample_t output[SIZE];
+	static adcsample_t prev[D]; // prev[0] = output[0 - D]
+
+	// Do calculations with previous output
+	for (unsigned int i = 0; i < D; i++)
+		output[i] = samples[i] + alpha * (prev[i] - 2048);
+
+	// Do calculations with current samples
+	for (unsigned int i = D; i < size; i++)
+		output[i] = samples[i] + alpha * (output[i - D] - 2048);
+
+	// Save outputs for next computation
+	for (unsigned int i = 0; i < D; i++)
+		prev[i] = output[size - (D - i)];
+
+	return output;
+}
-- 
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