(TCO 6) Write a C program to toggle PA2 of PORTA ON and OFF with a 1-ms delay af
ID: 663879 • Letter: #
Question
(TCO 6) Write a C program to toggle PA2 of PORTA ON and OFF with a 1-ms delay after each toggle. Assume that clock frequency is 6.25 MHz. Write inline assembly-language code inside of the delay function. (Points : 35)
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Explanation / Answer
#include #include #include #include #include #include #include #include #include #include #define SERVO0 PA0 #define SERVO1 PA1 #define SERVO2 PA2 #define SERVO3 PA3 #define MOSI_PIN PA6 #define SCK_PIN PA4 #define SS_PIN PA5 #define MIN_SERVO 76 // 0.608 ms is the minimum uptime #define MAX_SERVO 0xFFFF // Overflow should occur at roughly 40 Hz void init_servos(void); void set_servo(uint8_t , uint8_t); void disable_servos(void); void init_motors(void); void set_motor(uint8_t , uint8_t ); void disable_motors(void); void init_spi(void); void printByte(uint8_t value); unsigned int servo_values[4] = {0,0,0,0}; unsigned int servo_values_temp[4] = {0,0,0,0}; uint8_t servo_enabled[4] = {0,0,0,0}; volatile unsigned int next_servo_val = 0; volatile uint8_t toggle; int main(void) { uint8_t incoming_byte1=0; uint8_t incoming_byte2=0; uint8_t state = 0; _delay_ms(1); init_servos(); init_motors(); init_spi(); // init global interrupts sei(); while(1) { // Only do stuff if Pin A5 is low if(!(PINA & _BV(PA5))) { if(USISR & _BV(USIOIF)) { // Clear the flag USISR |= _BV(USIOIF); // Clear the counter just in case USISR &= 0xF0; if(state == 0) { incoming_byte1 = USIBR; if(incoming_byte1 == 0xFF) { disable_servos(); } else if(incoming_byte1 == 0xFE) { disable_motors(); } else { state = 1; } // printByte(incoming_byte1); } else { incoming_byte2 = USIBR; if(incoming_byte1 < 4) { set_servo(incoming_byte1, incoming_byte2); } else { set_motor(incoming_byte1, incoming_byte2); } state = 0; // printByte(incoming_byte2); } } } } return 1; } void init_spi() { // ensures the direction of the SPI port is all inputs DDRA &= (0xFF - _BV(MOSI_PIN) - _BV(SS_PIN) - _BV(SCK_PIN)); // Enable the counter interrupt, and 3-wire mode, use external clocking and sample on leading edge USICR = _BV(USIWM0) | _BV(USICS1) | _BV(USICS0); // _BV(USIOIE) | // Clear counter USISR &= 0xF0; } void init_servos() { DDRA |= _BV(SERVO0) | _BV(SERVO1) | _BV(SERVO2) | _BV(SERVO3); // Set pins to normal mode, set waveform to CTC mode (OCR1A becomes top) TCCR1A = 0x00; // Set clock divider to 64, counting frequency is one count/8us TCCR1B = _BV(WGM12) | _BV(CS11) | _BV(CS10); // Set overflows to occur every 40 Hz OCR1A = 3125; // Enable ocr1a and ocr1b interrupts TIMSK1 = _BV(OCIE1B) | _BV(OCIE1A); } void init_motors() { // set motor pins to output DDRA |= _BV(PA7); DDRB |= _BV(PB0) | _BV(PB1) | _BV(PB2); // Set to non-inverting fast PWM mode TCCR0A = 0xA3; //_BV(COM0A1) | _BV(COM0B1) | _BV(WGM01) | (WGM00); // Use the built-in 8 MHz oscillator for clocking TCCR0B = 0x01;//_BV(CS00); } /* Which combines the motor and direction of the motor, values: 4 - motor 1 forward 5 - motor 2 forward 6 - motor 1 backward 7 - motor 2 backward value is the power going to the motor */ void set_motor(uint8_t which, uint8_t value) { // Set motor 1 or 2 if(which == 4 || which == 6) { if(which == 4) PORTB |= _BV(PB1); else PORTB &= ~_BV(PB1); OCR0B = value; } else { if(which == 5) PORTB |= _BV(PB0); else PORTB &= ~_BV(PB0); OCR0A = value; } } void disable_motors() { OCR0A = 0; OCR0B = 0; } // Disables the timer1 interrupt and turns ports to 0, disabling the servos void disable_servos() { // Disables interrupts servo_enabled[0] = 0; servo_enabled[1] = 0; servo_enabled[2] = 0; servo_enabled[3] = 0; PORTA &= (0xFF - _BV(SERVO0) - _BV(SERVO1) - _BV(SERVO2) - _BV(SERVO3)); } // Turns servo pin to output and sets its value void set_servo(uint8_t which, uint8_t value) { // servo values over 250 turn power off to the servo if(value > 250) servo_enabled[which] = 0; else { servo_enabled[which] = 1; servo_values_temp[which] = value + MIN_SERVO; } } // For debugging only void printByte(uint8_t value) { PORTA |= _BV(SERVO3); _delay_us(5); PORTA &= (0xFF - _BV(SERVO3)); _delay_us(2); for(int i = 7; i >= 0; i--) { PORTA |= _BV(SERVO3); if((value>>i) & 0x01) _delay_us(25); else _delay_us(2); PORTA &= (0xFF - _BV(SERVO3)); _delay_us(20); } PORTA &= (0xFF - _BV(SERVO3)); _delay_us(5); PORTA |= _BV(SERVO3); _delay_us(2); PORTA &= (0xFF - _BV(SERVO3)); } /* Timer 1 compare A interrupt, acting as timer overflow. Set all servo pins high, then set the time to trigger output compare B (which turns them off) */ ISR(TIM1_COMPA_vect) { int i; // stop clock //TCCR1B = _BV(WGM12); for(i = 0; i < 4; i++) { servo_values[i] = servo_values_temp[i]; } // Set the first servo high if(servo_enabled[0] == 1) PORTA |= _BV(SERVO0); next_servo_val = 0; // now set the next interrupt to occur in current time plus the time of the next servo pulse OCR1B = servo_values[next_servo_val] + TCNT1; // Restart clock //TCCR1B = _BV(WGM12) | _BV(CS11); /* OCR1BH = servo_values[0]>>8; OCR1BL = servo_values[0];*/ } /* Timer 1 output compare B interrupt. Does the following: Checks to see if the current servo is 4, in which case just need to set low servo 3's signal and return. Else, check to see if the current servo is enabled, and set it's signal high Then, set the previous servo's signal low Now, set the next output compare to occur for some time from now specified by the current servo's value */ ISR(TIM1_COMPB_vect) { // Stop clock //TCCR1B = _BV(WGM12); // turn off the current servo pin PORTA &= (0xFF-_BV(next_servo_val)); // turn on the next one next_servo_val++; // if we've reach our limit, break out instead if(next_servo_val > 3) return; // if enabled, turn on the next one if(servo_enabled[next_servo_val] == 1) PORTA |= _BV(next_servo_val); // now set the next interrupt to occur in current time plus the time of the next servo pulse OCR1B = servo_values[next_servo_val] + TCNT1; // Restart clock //TCCR1B = _BV(WGM12) | _BV(CS11); /* OCR1BL = next_servo_val + TCNT1L; OCR1BH = servo_values[next_servo_val]>>8 + TCNT1H;*/ } /* ISR(USI_OVF_vect)//, ISR_NOBLOCK) { if(toggle < 2) { set_servo(0, 255); toggle++; } else { set_servo(0,0); toggle = 0; } // Clear the interrupt - somehow this isn't being done in the ISR USISR |= _BV(USIOIF); // Clear the counter just in case USISR &= 0xF0; if(state == 0) { incoming_byte1 = USIBR; if(incoming_byte1 == 0xFF) { disable_servos(); } else if(incoming_byte1 == 0xFE) { disable_vbr(); } else { state = 1; } printByte(incoming_byte1); } else { incoming_byte2 = USIBR; if(incoming_byte1 < 4) { set_servo(incoming_byte1, incoming_byte2); } else { set_vbr(incoming_byte1, incoming_byte2); } state = 0; printByte(incoming_byte2); } }*/Related Questions
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