use timers to measure pulse and bits. megacode detecting added
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43257b8ace
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134
pic/MDR/MDR.c
134
pic/MDR/MDR.c
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@ -47,6 +47,8 @@
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/* variables */
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static uint8_t switches; /* save the last switch state */
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#define START 208 /* starting timer 0 value to wait up to 12ms in start_timer*/
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static uint8_t code[3]; /* the received code (24 bits) */
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/* configuration bits */
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uint16_t __at(_CONFIG1) __CONFIG1 = _FCMEN_ON & /* enable fail-safe clock monitor */
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@ -59,9 +61,17 @@ uint16_t __at(_CONFIG1) __CONFIG1 = _FCMEN_ON & /* enable fail-safe clock monito
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_PWRTE_ON & /* use power-up timer */
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_WDTE_OFF & /* disable watchdog */
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_FOSC_XT; /* use external resonator */
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uint16_t __at(_CONFIG2) __CONFIG2 = _LVP_ON & /* enable low voltage programming */
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/* DEBUG is not present in library, but I don't use it */
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_BORV_LO & /* low borwn out voltage */
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_STVREN_ON & /* enable reset on stack overflow */
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_PLLEN_OFF & /* don't use 4X PLL, for longer timer */
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_WRT_OFF; /* no flash write protect */
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/* initialize micro-conroller */
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void init (void) {
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/* configure IO */
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ANSELA = 0; /* all pins are digital */
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ANSELB = 0; /* all pins are digital */
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TRISA |= RADIO; /* radio signal is an input */
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@ -70,25 +80,67 @@ void init (void) {
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TRISB &= ~(LED|MEMORY_CLK|MEMORY_DATA); /* LED is I2C memory are outputs */
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led_off(); /* starting state */
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/* configure switches input */
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IOCIE = 1; /* enable interrupt on individual GPIO (typo in the lib) */
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IOCIF = 0; /* clear GPIO interrupt */
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IOCBP |= (SWITCH1|SWITCH2); /* enable interrupt when switch is released */
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IOCBN |= (SWITCH1|SWITCH2); /* enable interrupt when switch is pressed */
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switches = PORTB; /* save current switch state */
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/*
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T1CON = _T1CKPS1 | _T1CKPS0; // set prescaler to 8
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// 0 is set per default, but just be sure
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TMR1ON = 0; // stop timer 1
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TMR1GE = 0; // enable timer 1
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TMR1CS = 0; // use internal clock / 4 (=1MHz)
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TMR1IF = 0; // clear interrupt
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PIE1 = 1; // enable timer 1 interrupt
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PEIE = 1; // enable timer interrupt
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*/
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/* use timer 0 to measure bitframes timing */
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TMR0CS = 1; /* disable timer 0 (T0CKI/RA4 is connected to ground) */
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TMR0SE = 0; /* increment timer0 on low to high edge ((T0CKI/RA4 is connected to ground) */
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PSA = 0; /* use presacler for timer 0 */
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PS0 = 1; /* use prescaler of 256 */
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PS1 = 1; /* use prescaler of 256 */
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PS2 = 1; /* use prescaler of 256 */
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TMR0IE = 1; /* enable timer 0 interrupt */
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TMR0IF = 0; /* clear timer 0 interrupt */
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/* use timer 2 to measure pulse durations (max 16.384ms) */
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TMR2ON = 1; /* stop timer 2 */
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T2CKPS0 = 1; /* use prescaler of 64 */
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T2CKPS1 = 1; /* use prescaler of 64 */
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T2OUTPS0 = 0; /* use postscale of 1 */
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T2OUTPS1 = 0; /* use postscale of 1 */
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T2OUTPS2 = 0; /* use postscale of 1 */
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T2OUTPS3 = 0; /* use postscale of 1 */
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PR2 = 0xff; /* set interrupt on overflow */
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TMR2IE = 1; /* enable timer 2 interrupt */
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TMR2IF = 0; /* clear timer 2 interrupt */
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PEIE = 1; /* enable peripheral interrupt (for timer 2) */
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GIE = 1; /* golablly enable interrupts */
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}
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/* start timer to measure bitframe
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* returns the time (in 0.256ms steps) since the last start
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* stops after 12ms (then it returns 0)
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*/
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uint8_t start_bit_timer(void)
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{
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/* uses timer 0
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* speed is Fosc/4 with a prescaler of 256
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* each tick should be 1.0/((4000000/4)/256) = 0.0002560163850486431 seconds
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* since there should be one pulse every 6ms, only wait up to 12ms
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*/
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uint8_t time = TMR0-START; /* remember the time passed */
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TMR0 = START; /* reset timer */
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TMR0CS = 0; /* enable timer 0 */
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return time;
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}
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/* start timer to measure pulse length
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* read the time from TMR2
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* step is 0.064ms
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* stops at 0xff (16.384ms)
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*/
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void start_pulse_timer()
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{
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TMR2 = 0; /* reset timer counter */
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TMR2ON = 1; /* start timer 2 */
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}
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/* funcion called on interrupts */
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/* interrupt 0 is only one on PIC16 */
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static void interrupt(void) __interrupt 0
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@ -98,9 +150,9 @@ static void interrupt(void) __interrupt 0
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switches ^= PORTB; /* figure out which switch changed */
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if (switches&SWITCH1) { /* switch 1 changed */
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if (PORTB&SWITCH1) { /* switch 1 released */
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led_off();
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led_off(); /* reset LED */
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} else { /* switch 1 pressed */
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led_on();
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led_on(); /* test LED */
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}
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}
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if (switches&SWITCH2) { /* switch 2 changed */
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@ -110,14 +162,68 @@ static void interrupt(void) __interrupt 0
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}
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IOCIF = 0; /* clear GPIO interrupt */
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}
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if (TMR0IF) { /* timer 0 overflow. no bit within required time */
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TMR0CS = 1; /* stop timer 1 */
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TMR0 = START; /* reset timer */
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TMR0IF = 0; /* clear timer 0 interrupt */
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}
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if (TMR2IF) { /* timer 2 overflow. long pulse */
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TMR2ON = 0; /* stop timer 2 */
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TMR2 = 0xff; /* set timer 2 count to maximum */
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TMR2IF = 0; /* clear timer 2 interrupt */
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}
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}
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void main (void)
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{
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uint8_t rx = 0; /* are we receiving a pulse */
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uint8_t bit = 0; /* the current received bit */
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uint8_t time = 0; /* time since previous bitframe start, in 0.256ms steps */
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init(); /* configure micro-controller */
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led_on();
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while (1) { /* a microcontroller runs forever */
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// sleep(); /* sleep to save power */
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/* I can't go to sleep to safe power
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* the RADIO is connected to RA0, but port A does not support interrupt on change
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* the timers are off in sleep, except for timer 1 when externally driven, but this is not our case
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* the watchdog can only wake up every 1ms, but that is not fast enough and a pulse could be missed
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*/
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if (rx==0 && (PORTA&RADIO)) { /* pulse detected */
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rx = 1; /* mark receiving start to wait until pulse is finished */
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start_pulse_timer();
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} else if (rx!=0 && !(PORTA&RADIO)) { /* end of pulse */
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rx = 0;
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if (TMR2>=14) { /* only observe pulses >0.9ms */
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/* pulse should be 1ms, but 1.2ms are used in the field
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* the first transmission can sometimes be detected a 10ms, even with a 1ms pulse
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* this is why the fallinf edge is used
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*/
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if (bit>0) { /* following pulses */
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time += start_bit_timer(); /* get time and start measure time for next pulse */
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if (time>=27 && time<=35) { /* pulse between 7 and 9 ms after previous bitframe start is a 0 */
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time = 8; /* pulse is 2ms after bitframe start */
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code[bit/8] &= ~(1<<(7-(bit%8))); /* store first bit=0 */
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bit++; /* wait for next bit */
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} else if (time>=40 && time<=47) { /* pulse between 10 and 12 ms after previous bitframe start is a 0 */
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time = 20; /* the sync pulse is 5ms after bitframe start */
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code[bit/8] |= 1<<(7-(bit%8)); /* store first bit=1 */
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bit++; /* wait for next bit */
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} else { /* unexpected pulse. code is broken */
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bit = 0; /* restart from beginning for new code */
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}
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if (bit==24) { /* received all 24 bits */
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led_on();
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}
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}
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if (bit==0) { /* sync pulse (can be the current one it it is not a continuation */
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start_bit_timer(); /* measure time until next bit */
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time = 20; /* the sync pulse is 5ms after bitframe start */
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code[bit/8] |= 1<<(7-(bit%8)); /* store first bit=1 */
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bit++; /* wait for next bit */
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}
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}
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}
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}
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}
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