main.cpp

00001 #include "mbed.h"
00002 #include "LPC17xx.h"
00003 #include "TextLCD.h"
00004  
00005 // declare hardware you're going to use, mostly copied from example code in previous assignments / Dagens piazza post
00006 volatile unsigned short timer_count;
00007 Serial pc(USBTX, USBRX);
00008 TextLCD lcd(p15, p16, p17, p18, p19, p20, TextLCD::LCD20x4); // rs, e, d4-d7
00009 
00010 // declare constants used for counting
00011 int running = 0;
00012 char mins_tens = '0';
00013 char mins_ones = '0';
00014 char seconds_tens = '0';
00015 char seconds_ones = '0';
00016 char ms_tens = '0';
00017 char ms_ones = '0';
00018 
00019 
00020 // hardware interrupt handler, adapted from code in piazza post by Dagaen
00021 extern "C" void TIMER0_IRQHandler (void)
00022 {
00023 if((LPC_TIM0->IR & 0x01) == 0x01)   // if MR0 interrupt, proceed
00024     {
00025     LPC_TIM0->IR |= 1 << 0;         // Clear MR0 interrupt flag
00026     timer_count++;                  //increment timer_count
00027     }
00028 }
00029  
00030 // init the hardware interrupt (timer0), adapted same as above
00031 void timer0_init(void)
00032 {
00033     LPC_SC->PCONP |=1<1;            //timer0 power on
00034     LPC_SC-> PCLKSEL0 |= 1 << 2;    // set timer clock to CCLCK nondivided (1 clock cycle = 1 increment)
00035     LPC_TIM0->MR0 = 1000000;          //100mhz clock cycle, 1 cycle = 10ns, 10ms = 10 000 000 ns = 1M cycles
00036     LPC_TIM0->MCR = 3;              //interrupt and reset control
00037                                     //3 = Interrupt & reset timer0 on match (111) sets all three bits
00038     NVIC_EnableIRQ(TIMER0_IRQn);    //enable timer0 interrupt
00039 }
00040 
00041 // update the display with the global timer values
00042 void update_display(void){
00043      // initialize the display, start at 0, paused
00044     // first MM
00045     lcd.locate(0,0);
00046     lcd.putc(mins_tens);
00047     lcd.locate(1,0);
00048     lcd.putc(mins_ones);
00049     // then : 
00050     lcd.locate(2,0);
00051     lcd.putc(':');
00052     // then SS
00053     lcd.locate(3,0);
00054     lcd.putc(seconds_tens);
00055     lcd.locate(4,0);
00056     lcd.putc(seconds_ones);
00057     // then :
00058     lcd.locate(5,0);
00059     lcd.putc(':');
00060     // then mS
00061     lcd.locate(6,0);
00062     lcd.putc(ms_tens);
00063     lcd.locate(7,0);
00064     lcd.putc(ms_ones);
00065 }
00066 
00067 // reset global values to 0
00068 void reset(void){
00069     mins_tens = '0';
00070     mins_ones = '0';
00071     seconds_tens = '0';
00072     seconds_ones = '0';
00073     ms_tens = '0';
00074     ms_ones = '0';
00075 }
00076 
00077 // hw interrupt callback, deal with the keyboard input from PC
00078 void kb_interrupt() {
00079     
00080     // get the char, put it on the PC command line
00081     char a = pc.getc();
00082     pc.putc(a);
00083     // if the char is S, make sure TCR's relevant bit is set
00084     if(a == 's'){
00085         // start timer
00086         running = 1;
00087         LPC_TIM0->TCR |= 1 << 0;
00088     // if the char is p, clear TCR, pausing the timer
00089     }else if (a == 'p'){
00090         LPC_TIM0->TCR = 0;
00091         running = 0;
00092     // if the char is r, reset the timer, potentially update display independent of clk interrupt if stopped
00093     }else if (a == 'r'){
00094         reset();
00095         if(!running){
00096             update_display();
00097         }
00098     }else{
00099         // do nothing for invalid char
00100     }
00101 }
00102 
00103  
00104 int main (void) 
00105 {
00106     
00107     // connect the serial device (PC keybd) to the interrupt
00108     pc.attach(&kb_interrupt);
00109     
00110     // reset the counters, display the original 00:00:00 state
00111     reset();
00112     update_display();
00113     
00114     
00115     //init vars, start timer
00116     timer_count = 0;
00117     timer0_init();
00118     
00119     // main program loop
00120     while(true){
00121         // on 10ms interrupt
00122         if(timer_count){
00123             // set timer count to 0 every 10ms
00124             timer_count = 0;
00125             
00126             // count up on 10ms interrupt, make sure counter updates properly
00127             
00128             // update ms ones
00129             int msones_carry_flag = 0;
00130             if(ms_ones == '9'){
00131                 ms_ones = '0';
00132                 msones_carry_flag = 1;
00133             }else{
00134                 ms_ones++;
00135             }
00136             
00137             // update ms tens
00138             int mstens_carry_flag = 0;
00139             if(msones_carry_flag){
00140                 if(ms_tens == '9'){
00141                     ms_tens = '0';
00142                     mstens_carry_flag = 1;
00143                 }else{
00144                     ms_tens++;
00145                 } 
00146             }
00147             
00148             // update sec ones
00149             int seconds_ones_carry_flag = 0;
00150             if(mstens_carry_flag){
00151                 if(seconds_ones == '9'){
00152                     seconds_ones = '0';
00153                     seconds_ones_carry_flag = 1;
00154                 }else{
00155                     seconds_ones++;
00156                 } 
00157             }
00158             
00159             // update sec tens
00160             int seconds_tens_carry_flag = 0;
00161             if(seconds_ones_carry_flag){
00162                 if(seconds_tens == '5'){
00163                     seconds_tens = '0';
00164                     seconds_tens_carry_flag = 1;
00165                 }else{
00166                     seconds_tens++;
00167                 } 
00168             }
00169             
00170             // update mins ones
00171             int mins_ones_carry_flag = 0;
00172             if(seconds_tens_carry_flag){
00173                 if(mins_ones == '9'){
00174                     mins_ones = '0';
00175                     mins_ones_carry_flag = 1;
00176                 }else{
00177                     mins_ones++;
00178                 } 
00179             }
00180             
00181             // update mins tens
00182             if(mins_ones_carry_flag){
00183                 if(mins_ones == '9'){
00184                     mins_ones = '0';
00185                     mins_ones_carry_flag = 1;
00186                 }else{
00187                     mins_ones++;
00188                 } 
00189             }
00190             
00191             // update display with new vals
00192             update_display();
00193         
00194         }
00195 
00196     }   
00197 }