Import FreqMeasure version 1.0

FreqMeasure.cpp

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+/* FreqMeasure Library, for measuring relatively low frequencies
+ * http://www.pjrc.com/teensy/td_libs_FreqMeasure.html
+ * Copyright (c) 2011 PJRC.COM, LLC - Paul Stoffregen <paul@pjrc.com>
+ *
+ * Version 1.0
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "FreqMeasure.h"
+#include "util/capture.h"
+
+#define FREQMEASURE_BUFFER_LEN 12
+static volatile uint32_t buffer_value[FREQMEASURE_BUFFER_LEN];
+static volatile uint8_t buffer_head;
+static volatile uint8_t buffer_tail;
+static uint16_t capture_msw;
+static uint32_t capture_previous;
+
+
+void FreqMeasureClass::begin(void)
+{
+	capture_init();
+	capture_msw = 0;
+	capture_previous = 0;
+	buffer_head = 0;
+	buffer_tail = 0;
+	capture_start();
+}
+
+uint8_t FreqMeasureClass::available(void)
+{
+	uint8_t head, tail;
+
+	head = buffer_head;
+	tail = buffer_tail;
+	if (head >= tail) return head - tail;
+	return FREQMEASURE_BUFFER_LEN + head - tail;
+}
+
+uint32_t FreqMeasureClass::read(void)
+{
+	uint8_t head, tail;
+	uint32_t value;
+
+	head = buffer_head;
+	tail = buffer_tail;
+	if (head == tail) return 0xFFFFFFFF;
+	tail = tail + 1;
+	if (tail >= FREQMEASURE_BUFFER_LEN) tail = 0;
+	value = buffer_value[tail];
+	buffer_tail = tail;
+	return value;
+}
+
+void FreqMeasureClass::end(void)
+{
+	capture_shutdown();
+}
+
+
+ISR(TIMER_OVERFLOW_VECTOR)
+{
+	capture_msw++;
+}
+
+ISR(TIMER_CAPTURE_VECTOR)
+{
+	uint16_t capture_lsw;
+	uint32_t capture, period;
+	uint8_t i;
+
+	// get the timer capture
+	capture_lsw = capture_read();
+	// Handle the case where but capture and overflow interrupts were pending
+	// (eg, interrupts were disabled for a while), or where the overflow occurred
+	// while this ISR was starting up.  However, if we read a 16 bit number that
+	// is very close to overflow, then ignore any overflow since it probably
+	// just happened.
+	if (capture_overflow() && capture_lsw < 0xFF00) {
+		capture_overflow_reset();
+		capture_msw++;
+	}
+	// compute the waveform period
+	capture = ((uint32_t)capture_msw << 16) | capture_lsw;
+	period = capture - capture_previous;
+	capture_previous = capture;
+	// store it into the buffer
+	i = buffer_head + 1;
+	if (i >= FREQMEASURE_BUFFER_LEN) i = 0;
+	if (i != buffer_tail) {
+		buffer_value[i] = period;
+		buffer_head = i;
+	}
+}
+
+
+FreqMeasureClass FreqMeasure;
+

FreqMeasure.h

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+#ifndef FreqMeasure_h
+#define FreqMeasure_h
+
+#include <inttypes.h>
+
+class FreqMeasureClass {
+public:
+	static void begin(void);
+	static uint8_t available(void);
+	static uint32_t read(void);
+	static void end(void);
+};
+
+extern FreqMeasureClass FreqMeasure;
+
+#endif
+

README.md

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+#FreqMeasure Library#
+
+FreqMeasure measures the elapsed time during each cycle of an input frequency.
+
+http://www.pjrc.com/teensy/td_libs_FreqMeasure.html
+
+![FreqMeasure and Test Equipment](http://www.pjrc.com/teensy/td_libs_FreqMeasure_1.jpg)

examples/LCD_Output/LCD_Output.pde

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+/* FreqMeasure - Example with LCD output
+ * http://www.pjrc.com/teensy/td_libs_FreqMeasure.html
+ *
+ * This example code is in the public domain.
+ */
+#include <FreqMeasure.h>
+#include <LiquidCrystal.h>
+
+LiquidCrystal lcd(5, 4, 3, 2, 1, 0);
+
+void setup() {
+  Serial.begin(57600);
+  lcd.begin(8, 2);
+  lcd.print("Freq:");
+  FreqMeasure.begin();
+}
+
+double sum=0;
+int count=0;
+
+void loop() {
+  if (FreqMeasure.available()) {
+    // average several reading together
+    sum = sum + FreqMeasure.read();
+    count = count + 1;
+    if (count > 30) {
+      double frequency = F_CPU / (sum / count);
+      lcd.setCursor(0, 1);
+      lcd.print(frequency);
+      lcd.print("       ");
+      sum = 0;
+      count = 0;
+    }
+  }
+}
+

examples/Serial_Output/Serial_Output.pde

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+/* FreqMeasure - Example with serial output
+ * http://www.pjrc.com/teensy/td_libs_FreqMeasure.html
+ *
+ * This example code is in the public domain.
+ */
+#include <FreqMeasure.h>
+
+void setup() {
+  Serial.begin(57600);
+  FreqMeasure.begin();
+}
+
+double sum=0;
+int count=0;
+
+void loop() {
+  if (FreqMeasure.available()) {
+    // average several reading together
+    sum = sum + FreqMeasure.read();
+    count = count + 1;
+    if (count > 30) {
+      double frequency = F_CPU / (sum / count);
+      Serial.println(frequency);
+      sum = 0;
+      count = 0;
+    }
+  }
+}
+

keywords.txt

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+FreqMeasure	KEYWORD1
+begin	KEYWORD2
+available	KEYWORD2
+read	KEYWORD2
+end	KEYWORD2