Added interrupt driven Timer for serial IO

Libraries/Timer3/TimerThree.cpp

@@ -0,0 +1,102 @@
+/*
+ *  Interrupt and PWM utilities for 16 bit Timer3 on ATmega168/328
+ *  Original code by Jesse Tane for http://labs.ideo.com August 2008
+ *  Modified March 2009 by Jérôme Despatis and Jesse Tane for ATmega328 support
+ *  Modified June 2009 by Michael Polli and Jesse Tane to fix a bug in setPeriod() which caused the timer to stop
+ *  Modified Oct 2009 by Dan Clemens to work with timer3 of the ATMega1280 or Arduino Mega
+ *
+ *  This is free software. You can redistribute it and/or modify it under
+ *  the terms of Creative Commons Attribution 3.0 United States License. 
+ *  To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/us/ 
+ *  or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.
+ *
+ */
+
+#include "TimerThree.h"
+
+TimerThree Timer3;              // preinstatiate
+
+ISR(TIMER3_OVF_vect)          // interrupt service routine that wraps a user defined function supplied by attachInterrupt
+{
+  Timer3.isrCallback();
+}
+
+void TimerThree::initialize(long microseconds)
+{
+  TCCR3A = 0;                 // clear control register A 
+  TCCR3B = _BV(WGM13);        // set mode as phase and frequency correct pwm, stop the timer
+  setPeriod(microseconds);
+}
+
+void TimerThree::setPeriod(long microseconds)
+{
+  long cycles = (F_CPU * microseconds) / 2000000;                                // the counter runs backwards after TOP, interrupt is at BOTTOM so divide microseconds by 2
+  if(cycles < RESOLUTION)              clockSelectBits = _BV(CS10);              // no prescale, full xtal
+  else if((cycles >>= 3) < RESOLUTION) clockSelectBits = _BV(CS11);              // prescale by /8
+  else if((cycles >>= 3) < RESOLUTION) clockSelectBits = _BV(CS11) | _BV(CS10);  // prescale by /64
+  else if((cycles >>= 2) < RESOLUTION) clockSelectBits = _BV(CS12);              // prescale by /256
+  else if((cycles >>= 2) < RESOLUTION) clockSelectBits = _BV(CS12) | _BV(CS10);  // prescale by /1024
+  else        cycles = RESOLUTION - 1, clockSelectBits = _BV(CS12) | _BV(CS10);  // request was out of bounds, set as maximum
+  ICR3 = pwmPeriod = cycles;                                                     // ICR1 is TOP in p & f correct pwm mode
+  TCCR3B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12));
+  TCCR3B |= clockSelectBits;                                                     // reset clock select register
+}
+
+void TimerThree::setPwmDuty(char pin, int duty)
+{
+  unsigned long dutyCycle = pwmPeriod;
+  dutyCycle *= duty;
+  dutyCycle >>= 10;
+  if(pin == 5) OCR3A = dutyCycle;
+  if(pin == 2) OCR3B = dutyCycle;
+  if(pin == 3) OCR3C = dutyCycle;
+}
+
+void TimerThree::pwm(char pin, int duty, long microseconds)  // expects duty cycle to be 10 bit (1024)
+{
+  if(microseconds > 0) setPeriod(microseconds);
+  
+	// sets data direction register for pwm output pin
+	// activates the output pin
+  if(pin == 5) { DDRE |= _BV(PORTE3); TCCR3A |= _BV(COM3A1); }
+  if(pin == 2) { DDRE |= _BV(PORTE4); TCCR3A |= _BV(COM3B1); }
+  if(pin == 3) { DDRE |= _BV(PORTE5); TCCR3A |= _BV(COM3C1); }
+  setPwmDuty(pin, duty);
+  start();
+}
+
+void TimerThree::disablePwm(char pin)
+{
+  if(pin == 5) TCCR3A &= ~_BV(COM3A1);   // clear the bit that enables pwm on PE3
+  if(pin == 2) TCCR3A &= ~_BV(COM3B1);   // clear the bit that enables pwm on PE4
+  if(pin == 3) TCCR3A &= ~_BV(COM3C1);   // clear the bit that enables pwm on PE5
+}
+
+void TimerThree::attachInterrupt(void (*isr)(), long microseconds)
+{
+  if(microseconds > 0) setPeriod(microseconds);
+  isrCallback = isr;                                       // register the user's callback with the real ISR
+  TIMSK3 = _BV(TOIE1);                                     // sets the timer overflow interrupt enable bit
+  sei();                                                   // ensures that interrupts are globally enabled
+  start();
+}
+
+void TimerThree::detachInterrupt()
+{
+  TIMSK3 &= ~_BV(TOIE1);                                   // clears the timer overflow interrupt enable bit 
+}
+
+void TimerThree::start()
+{
+  TCCR3B |= clockSelectBits;
+}
+
+void TimerThree::stop()
+{
+  TCCR3B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12));          // clears all clock selects bits
+}
+
+void TimerThree::restart()
+{
+  TCNT3 = 0;
+}

Libraries/Timer3/TimerThree.h

@@ -0,0 +1,41 @@
+/*
+ *  Interrupt and PWM utilities for 16 bit Timer3 on ATmega168/328
+ *  Original code by Jesse Tane for http://labs.ideo.com August 2008
+ *  Modified March 2009 by Jérôme Despatis and Jesse Tane for ATmega328 support
+ *  Modified June 2009 by Michael Polli and Jesse Tane to fix a bug in setPeriod() which caused the timer to stop
+ *
+ *  This is free software. You can redistribute it and/or modify it under
+ *  the terms of Creative Commons Attribution 3.0 United States License. 
+ *  To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/us/ 
+ *  or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.
+ *
+ */
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+
+#define RESOLUTION 65536    // Timer3 is 16 bit
+
+class TimerThree
+{
+  public:
+  
+    // properties
+    unsigned int pwmPeriod;
+    unsigned char clockSelectBits;
+
+    // methods
+    void initialize(long microseconds=1000000);
+    void start();
+    void stop();
+    void restart();
+    void pwm(char pin, int duty, long microseconds=-1);
+    void disablePwm(char pin);
+    void attachInterrupt(void (*isr)(), long microseconds=-1);
+    void detachInterrupt();
+    void setPeriod(long microseconds);
+    void setPwmDuty(char pin, int duty);
+    void (*isrCallback)();
+};
+
+extern TimerThree Timer3;

Universal_Serial_Adapter/Libraries/Timer3/TimerThree.cpp

@@ -0,0 +1,102 @@
+/*
+ *  Interrupt and PWM utilities for 16 bit Timer3 on ATmega168/328
+ *  Original code by Jesse Tane for http://labs.ideo.com August 2008
+ *  Modified March 2009 by Jérôme Despatis and Jesse Tane for ATmega328 support
+ *  Modified June 2009 by Michael Polli and Jesse Tane to fix a bug in setPeriod() which caused the timer to stop
+ *  Modified Oct 2009 by Dan Clemens to work with timer3 of the ATMega1280 or Arduino Mega
+ *
+ *  This is free software. You can redistribute it and/or modify it under
+ *  the terms of Creative Commons Attribution 3.0 United States License. 
+ *  To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/us/ 
+ *  or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.
+ *
+ */
+
+#include "TimerThree.h"
+
+TimerThree Timer3;              // preinstatiate
+
+ISR(TIMER3_OVF_vect)          // interrupt service routine that wraps a user defined function supplied by attachInterrupt
+{
+  Timer3.isrCallback();
+}
+
+void TimerThree::initialize(long microseconds)
+{
+  TCCR3A = 0;                 // clear control register A 
+  TCCR3B = _BV(WGM13);        // set mode as phase and frequency correct pwm, stop the timer
+  setPeriod(microseconds);
+}
+
+void TimerThree::setPeriod(long microseconds)
+{
+  long cycles = (F_CPU * microseconds) / 2000000;                                // the counter runs backwards after TOP, interrupt is at BOTTOM so divide microseconds by 2
+  if(cycles < RESOLUTION)              clockSelectBits = _BV(CS10);              // no prescale, full xtal
+  else if((cycles >>= 3) < RESOLUTION) clockSelectBits = _BV(CS11);              // prescale by /8
+  else if((cycles >>= 3) < RESOLUTION) clockSelectBits = _BV(CS11) | _BV(CS10);  // prescale by /64
+  else if((cycles >>= 2) < RESOLUTION) clockSelectBits = _BV(CS12);              // prescale by /256
+  else if((cycles >>= 2) < RESOLUTION) clockSelectBits = _BV(CS12) | _BV(CS10);  // prescale by /1024
+  else        cycles = RESOLUTION - 1, clockSelectBits = _BV(CS12) | _BV(CS10);  // request was out of bounds, set as maximum
+  ICR3 = pwmPeriod = cycles;                                                     // ICR1 is TOP in p & f correct pwm mode
+  TCCR3B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12));
+  TCCR3B |= clockSelectBits;                                                     // reset clock select register
+}
+
+void TimerThree::setPwmDuty(char pin, int duty)
+{
+  unsigned long dutyCycle = pwmPeriod;
+  dutyCycle *= duty;
+  dutyCycle >>= 10;
+  if(pin == 5) OCR3A = dutyCycle;
+  if(pin == 2) OCR3B = dutyCycle;
+  if(pin == 3) OCR3C = dutyCycle;
+}
+
+void TimerThree::pwm(char pin, int duty, long microseconds)  // expects duty cycle to be 10 bit (1024)
+{
+  if(microseconds > 0) setPeriod(microseconds);
+  
+	// sets data direction register for pwm output pin
+	// activates the output pin
+  if(pin == 5) { DDRE |= _BV(PORTE3); TCCR3A |= _BV(COM3A1); }
+  if(pin == 2) { DDRE |= _BV(PORTE4); TCCR3A |= _BV(COM3B1); }
+  if(pin == 3) { DDRE |= _BV(PORTE5); TCCR3A |= _BV(COM3C1); }
+  setPwmDuty(pin, duty);
+  start();
+}
+
+void TimerThree::disablePwm(char pin)
+{
+  if(pin == 5) TCCR3A &= ~_BV(COM3A1);   // clear the bit that enables pwm on PE3
+  if(pin == 2) TCCR3A &= ~_BV(COM3B1);   // clear the bit that enables pwm on PE4
+  if(pin == 3) TCCR3A &= ~_BV(COM3C1);   // clear the bit that enables pwm on PE5
+}
+
+void TimerThree::attachInterrupt(void (*isr)(), long microseconds)
+{
+  if(microseconds > 0) setPeriod(microseconds);
+  isrCallback = isr;                                       // register the user's callback with the real ISR
+  TIMSK3 = _BV(TOIE1);                                     // sets the timer overflow interrupt enable bit
+  sei();                                                   // ensures that interrupts are globally enabled
+  start();
+}
+
+void TimerThree::detachInterrupt()
+{
+  TIMSK3 &= ~_BV(TOIE1);                                   // clears the timer overflow interrupt enable bit 
+}
+
+void TimerThree::start()
+{
+  TCCR3B |= clockSelectBits;
+}
+
+void TimerThree::stop()
+{
+  TCCR3B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12));          // clears all clock selects bits
+}
+
+void TimerThree::restart()
+{
+  TCNT3 = 0;
+}

Universal_Serial_Adapter/Libraries/Timer3/TimerThree.h

@@ -0,0 +1,41 @@
+/*
+ *  Interrupt and PWM utilities for 16 bit Timer3 on ATmega168/328
+ *  Original code by Jesse Tane for http://labs.ideo.com August 2008
+ *  Modified March 2009 by Jérôme Despatis and Jesse Tane for ATmega328 support
+ *  Modified June 2009 by Michael Polli and Jesse Tane to fix a bug in setPeriod() which caused the timer to stop
+ *
+ *  This is free software. You can redistribute it and/or modify it under
+ *  the terms of Creative Commons Attribution 3.0 United States License. 
+ *  To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/us/ 
+ *  or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.
+ *
+ */
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+
+#define RESOLUTION 65536    // Timer3 is 16 bit
+
+class TimerThree
+{
+  public:
+  
+    // properties
+    unsigned int pwmPeriod;
+    unsigned char clockSelectBits;
+
+    // methods
+    void initialize(long microseconds=1000000);
+    void start();
+    void stop();
+    void restart();
+    void pwm(char pin, int duty, long microseconds=-1);
+    void disablePwm(char pin);
+    void attachInterrupt(void (*isr)(), long microseconds=-1);
+    void detachInterrupt();
+    void setPeriod(long microseconds);
+    void setPwmDuty(char pin, int duty);
+    void (*isrCallback)();
+};
+
+extern TimerThree Timer3;

Universal_Serial_Adapter/Project.h

@@ -33,6 +33,9 @@
 #define voltagePinThreePointThree 41 // Pin controlling 3.3V TTL logic
 #define voltagePinFivePointZero   42 // Pin controlling 5V TTL logic
 
+// Timer pins
+#define timerThreePin 2 // Maps to Mega pin 12
+
 // Colors / theme of UI
 #define SPLASH_BACKGROUND ST7735_WHITE
 #define BACKGROUND        ST7735_BLACK

Universal_Serial_Adapter/Universal_Serial_Adapter.ino

@@ -22,9 +22,16 @@
 #include <SD.h>
 #include <SPI.h>
 
+#include <TimerThree.h>
+
 UI* ui;
 Config* config;
 
+// helper for interrupt method call
+void processSerial() {
+  config->processSerialData();
+}
+
 void setup() {
   Serial.begin(115200);
 
@@ -32,15 +39,17 @@ void setup() {
   config->setDefaults();
 
   ui = new UI();
+
+  // Setup serial IO on an interrupt timer
+  // ***THIS MUST BE DONE AFTER new Config()***
+  Timer3.initialize(100);                // initialize timer3, value in micro seconds
+  Timer3.pwm(timerThreePin, 512);        // setup pwm on appropriate pin, 50% duty cycle
+  Timer3.attachInterrupt(processSerial); // attaches method as a timer overflow interrupt
 }
 
 void loop() {
-  // Serial data is processed at multiple points to prevent
+  // Serial data is processed via an interrupt so isn't needed in the main loop
-  //   UI code from interfering with communication
-  config->processSerialData();
   ui->processInputEvents();
-  config->processSerialData();
   ui->processTimeoutEvents();
-  config->processSerialData();
 }