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Basic timer on mBed 1768
Fork of HelloWorld by
main.cpp
- Committer:
- jatinsha
- Date:
- 2014-09-28
- Revision:
- 2:253054128736
- Parent:
- 0:fb6bbc10ffa0
- Child:
- 3:d18d3609c800
File content as of revision 2:253054128736:
/* CIS 541 - Embedded Systems for Life Critical Applications Assignment3 Timer using mBed 1768 Developers - Jatin Sharma and Samarth Shah References 1. Timer : http://mbed.org/handbook/Timer 2. String format modifiers : http://www.cdf.toronto.edu/~ajr/209/notes/printf.html 3. Keyboard Input : http://mbed.org/handbook/SerialPC 4. Interrupt attach : http://mbed.org/handbook/Serial 5. Enum tutorial : http://stackoverflow.com/questions/1102542/how-to-define-an-enumerated-type-enum-in-c 6. */ #include "mbed.h" #include "TextLCD.h" // RS, E, D4 - D7 for 4 bit mode #define RS p15 #define E p16 #define D4 p17 #define D5 p18 #define D6 p19 #define D7 p20 #define interval 10 TextLCD lcd(RS, E, D4, D5, D6, D7, TextLCD::LCD16x2); Timer timerDisplay, timerReference; Serial pc(USBTX, USBRX); // tx, rx int miliSeconds, centiSeconds, seconds, minutes; int currentReferenceTime, previousReferenceTime; int calculatedTimeInterval, referenceTimeInterval, runningError; char keyboardInput; typedef enum {Running, Paused, Reset} state_t; state_t timerState = Reset; void callback() { // Keyboard input : you need to actually read from the serial to clear the RX interrupt if(keyboardInput = pc.getc()) { if((keyboardInput == 's' || keyboardInput == 'S')) { if(timerState == Reset) { timerReference.start(); timerDisplay.start(); timerState = Running; } } if((keyboardInput == 'p' || keyboardInput == 'P')) { if(timerState == Running) { timerReference.stop(); timerDisplay.stop(); timerState = Paused; } else if(timerState == Paused) { timerReference.start(); timerDisplay.start(); timerState = Running; } } if((keyboardInput == 'r' || keyboardInput == 'R')) { if(timerState == Paused) { // Reset timer timerReference.reset(); timerDisplay.reset(); timerState = Reset; // Reset variables miliSeconds = seconds = minutes = 0; currentReferenceTime = previousReferenceTime = 0; calculatedTimeInterval = referenceTimeInterval = runningError = 0; lcd.locate(0,0); lcd.printf("00:00:00"); lcd.locate(0,1); lcd.printf("000000"); } } } } int main() { // interrupt service routine pc.attach(&callback); // local variable miliSeconds = seconds = minutes = 0; currentReferenceTime = previousReferenceTime = 0; calculatedTimeInterval = referenceTimeInterval = runningError = 0; //timerReference.start(); //timerDisplay.start(); // Initial display work lcd.locate(0,0); lcd.printf("00:00:00"); while(1) { if( timerDisplay.read_ms() >= interval) { timerDisplay.reset(); // Calculate display variables miliSeconds += interval; centiSeconds += (miliSeconds / 10); miliSeconds %= 10; seconds += (centiSeconds / 100); centiSeconds %= 100; minutes += (seconds / 60); seconds %= 60; // Error correction using referenceClock currentReferenceTime = timerReference.read_us(); referenceTimeInterval = currentReferenceTime - previousReferenceTime; runningError += (referenceTimeInterval - interval*1000); //miliSeconds += runningError; previousReferenceTime = currentReferenceTime; // Display time on LCD lcd.locate(0,0); lcd.printf("%02d:%02d:%02d",minutes, seconds, centiSeconds); lcd.locate(0,1); lcd.printf("%06d", runningError); } } }