Initial firmware commit.

firmware/application/touch.cpp

@@ -0,0 +1,119 @@
+/*
+ * Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
+ *
+ * This file is part of PortaPack.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include "touch.hpp"
+
+namespace touch {
+
+struct Metrics {
+	const float x;
+	const float y;
+	const float r;
+};
+
+static Metrics calculate_metrics(const Frame frame) {
+	/* TODO: Yikes! M0 doesn't have floating point, so this code is
+	 * expensive! On the other hand, it seems to be working well (and
+	 * fast *enough*?), so maybe leave it alone at least for now.
+	 */
+
+	const auto x_max = frame.x.xp;
+	const auto x_min = frame.x.xn;
+	const auto x_range = x_max - x_min;
+	const auto x_position = (frame.x.yp + frame.x.yn) / 2;
+	const float x_norm = float(x_position - x_min) / x_range;
+
+	const auto y_max = frame.y.yn;
+	const auto y_min = frame.y.yp;
+	const auto y_range = y_max - y_min;
+	const auto y_position = (frame.y.xp + frame.y.xn) / 2;
+	const float y_norm = float(y_position - y_min) / y_range;
+
+	const auto z_max = frame.pressure.yp;
+	const auto z_min = frame.pressure.xn;
+	const auto z_range = z_max - z_min;
+	const auto z1_position = frame.pressure.xp;
+	const float z1_norm = float(z1_position - z_min) / z_range;
+	const auto z2_position = frame.pressure.yn;
+	const float z2_norm = float(z2_position - z_min) / z_range;
+
+	const float r_x_plate = 330.0f;
+	//const float r_y_plate = 600.0f;
+	const float r_touch = r_x_plate * x_norm * (z2_norm / z1_norm - 1.0f);
+
+	return {
+		.x = x_norm,
+		.y = y_norm,
+		.r = r_touch,
+	};
+}
+
+void Manager::feed(const Frame frame) {
+	// touch_debounce.feed(touch_raw);
+	const auto touch_raw = frame.touch;
+	//const auto touch_stable = touch_debounce.state();
+	const auto touch_stable = frame.touch;
+	bool touch_pressure = false;
+
+	// Only feed coordinate averaging if there's a touch.
+	// TODO: Separate threshold to gate coordinates for filtering?
+	if( touch_raw ) {
+		const auto metrics = calculate_metrics(frame);
+
+		// TODO: Add touch pressure hysteresis?
+		touch_pressure = (metrics.r < r_touch_threshold);
+		if( touch_pressure ) {
+			const float x = width_pixels * (metrics.x - calib_x_low) / calib_x_range;
+			filter_x.feed(x);
+			const float y = height_pixels * (calib_y_high - metrics.y) / calib_y_range;
+			filter_y.feed(y);
+		}
+	} else {
+		filter_x.reset();
+		filter_y.reset();
+	}
+
+	switch(state) {
+	case State::NoTouch:
+		if( touch_stable && touch_pressure ) {
+			if( point_stable() ) {
+				state = State::TouchDetected;
+				touch_started();
+			}
+		}
+		break;
+
+	case State::TouchDetected:
+		if( touch_stable && touch_pressure ) {
+			touch_moved();
+		} else {
+			state = State::NoTouch;
+			touch_ended();
+		}
+		break;
+
+	default:
+		state = State::NoTouch;
+		break;
+	}
+}
+
+} /* namespace touch */