Multiple non-blocking delays with 1 timer
本帖最后由 eva 于 2012-8-21 14:43 编辑This example shows you how to create multiple non-blocking delays with only one timer, using :
[*]timer 1
[*]interrupts
[*]arrays of pointers to functions
[*]structures
It is made for a P18F452 but it could be used with others pics with just minor adjustments.
The binary code is less than 2K, so that you can use the unlicenced mikroC compiler to build the HEX file.
/* * this source code shows how to use pic timers, interrupts, and arrays of pointers to functions * and how to make non-blocking multiples delays, using a single timer * * Bruno Gavand, march 2006 *
* * P18F452 @8Mhz, HS clock, EASYPIC2 / EASYPIC3 * pull-down on PORTB * pull-up on keyboard * enable PORTB, PORTC and PORTD LEDs * * pressing RB0 key will toggle PORTC after a 2s non-blocking delay * pressing RB1 key will toggle PORTD after a 3s non-blocking delay * * used ROM : 1676 bytes *//* * number of delayed keys, up to 255 */#define NBKEYS2/* * struct for one key */typedef struct { unsigned char flag ; // active = 1, 0 otherwise unsigned char ctr ; // counter of timer1 overflows void (*stop)() ; // pointer to a function to call after delay } KEY_STRUCT ; KEY_STRUCT keys ; // struct array/* * functions that do something visible for the example */void toggleC() { PORTC = ~PORTC ; // invert PORTC (toggle LEDs) }void toggleD() { PORTD = ~PORTD ; // invert PORTD (toggle LEDs) }/* * start to count down d milliseconds for key i */void keyStart(unsigned char i, unsigned long d) { KEY_STRUCT *k ; k = &keys ; // struct pointer if(k->flag == 0) // if free ? { d <<= 18 ; // multiply by 4 * 2 ^ 16 d /= 1000 ; // divide by 1000 because d /= (long)Clock_Khz() ; // clock frequency is known in Khz k->ctr = d ; // assign counter k->flag = 1 ; // set flag to start countdown in interrupt } }/* * interrupt vector */void interrupt() { if(PIR1.TMR1IF) // timer1 overflow, Fosc/(4 * 2^16) times per second { unsigned char i ; for(i = 0 ; i < NBKEYS ; i++) // for each keys { KEY_STRUCT *k ; k = &keys ; // get pointer to the key struct if(k->flag) // if key countdown activated { if(k->ctr) // if countdown in progress { k->ctr-- ; // count down } else { k->flag = 0 ; // count down reached 0, disable (k->stop)() ; // call user's function } } } PIR1.TMR1IF = 0 ; // reset timer1 interrupt flag } }/* * program starts here */void main() { unsigned char i ; ADCON1 |= 0x07; //PORTA as digital I/O PORTA = PORTB = PORTC = PORTD = 0 ; //clear ports TRISA = 0 ; // PORTA as output TRISB = 0b00000011 ; // 2 LSB of PORTB as inputs, others as outputs TRISC = 0 ; // PORTC as output TRISD = 0 ; // PORTD as output keys.stop = toggleC ; // assign user's function to first key keys.stop = toggleD ; // assign user's function to second key for(i = 0 ; i < NBKEYS ; i++) // for each keys { keys.flag = 0 ; // reset struct keys.ctr = 0 ; } T1CON.T1CKPS1 = 0 ; // no prescaler T1CON.T1CKPS0 = 0 ; // on timer1 T1CON.T1OSCEN = 0 ; // disable timer1 oscillator T1CON.TMR1CS = 0 ; // timer1 is on Fosc T1CON.TMR1ON = 1 ; // start timer1 INTCON.GIE = 1 ; // enable global interrupts INTCON.PEIE = 1 ; // enable peripheral interrupts PIE1.TMR1IE = 1 ; // enable timer1 overflow interrupts for(;;) // forever { if(PORTB.F0) // if RB0 key pressed { keyStart(0, 2000) ; // start key #0 countdown for 2000 ms } else if(PORTB.F1) // if RB1 key pressed { keyStart(1, 3000) ; // start key #1 countdown for 3000 ms } } }
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