OmnibotISR.c

// THIS IS A CODE SNIPPET ONLY AND WILL NOT RUN AT ALL ON ITS OWN!!
// Variables declared globally for interrupt use

// Start of channel interval
volatile uint16_t ch1_start = 0;
volatile uint16_t ch2_start = 0;
volatile uint16_t ch3_start = 0;
volatile uint16_t ch4_start = 0;
volatile uint16_t ch5_start = 0;
volatile uint16_t ch6_start = 0;

// State of channel (high 1 or low 0)
volatile uint8_t ch1_state = 0;
volatile uint8_t ch2_state = 0;
volatile uint8_t ch3_state = 0;
volatile uint8_t ch4_state = 0;
volatile uint8_t ch5_state = 0;
volatile uint8_t ch6_state = 0;

// Stick positions in us, initialized to neutral stick positions
volatile int16_t ch1 = 1500;
volatile int16_t ch2 = 1500;
volatile int16_t ch3 = 1500;
volatile int16_t ch4 = 1500;
volatile int16_t ch5 = 1500;
volatile int16_t ch6 = 1500;

// Flag is set after each cycle of RC pulses
volatile uint8_t start_flag = 0;

// THIS IS ONLY A FRAGMENT OF THE WORKING main()!!
int main(void) {
	// Setup Timer/Counter1 in normal mode with prescaler of 8
	// At F_CPU = 16MHz, F_TIMER1 = 2MHz, and T_TIMER1 = 0.5 us
	TCCR1B |= (1 << CS11);
	
	// Enable external pin change interrupt 1 (PCINT1) for all 6 RC channels
	PCICR |= (1 << PCIE1);
	PCMSK1 |= (1 << PCINT8) | (1 << PCINT9) | (1 << PCINT10) | (1 << PCINT11) | (1 << PCINT12) | (1 << PCINT13);
	sei();		// Set the Global Interrupt Enable flag so that interrupts can be processed
	
	// Loop forever
	while(1) {		
		// Only update motor speeds after each full cycle of RC pulses
		if(start_flag == 1) {
			// CODE HERE WOULD USE THE RC CHANNEL VALUES TO UPDATE MOTOR SPEEDS AND DIRECTIONS
			start_flag = 0;		// Reset flag after speeds have updated
		}
	}
}

ISR (PCINT1_vect) {
	// Read six RC channels on PC0/PCINT8 (Ch1) to PC5/PCINT13 (Ch6)
	// Check to see if it is a rising edge for each channel to start timing
	// Falling edge to stop timing
	uint16_t currentTime = TCNT1 / 2;		// Read Timer/Counter1 in microseconds
	
	if(PINC & (1 << PORTC0)) {		// Channel 1
		if(ch1_state == 0) {
			TCNT1 = 0;			// Reset timer at start of ch1 only
			ch1_start = 0;
			ch1_state = 1;
			start_flag = 1;		// Set flag to update motor speeds & directions
		}
	} else if((PINC & (1 << PORTC0)) == 0) {
		if(ch1_state == 1) {
			ch1 = currentTime - ch1_start;
			ch1_state = 0;
		}
	}
	
	if(PINC & (1 << PORTC1)) {		//Channel 2
		if(ch2_state == 0) {
			ch2_start = currentTime;
			ch2_state = 1;
		}
	} else if((PINC & (1 << PORTC1)) == 0) {
		if(ch2_state == 1) {
			ch2 = currentTime - ch2_start;
			ch2_state = 0;
		}
	}
	
	if(PINC & (1 << PORTC2)) {		//Channel 3
		if(ch3_state == 0) {
			ch3_start = currentTime;
			ch3_state = 1;
		}
	} else if((PINC & (1 << PORTC2)) == 0) {
		if(ch3_state == 1) {
			ch3 = currentTime - ch3_start;
			ch3_state = 0;
		}
	}
	
	if(PINC & (1 << PORTC3)) {		//Channel 4
		if(ch4_state == 0) {
			ch4_start = currentTime;
			ch4_state = 1;
		}
	} else if((PINC & (1 << PORTC3)) == 0) {
		if(ch4_state == 1) {
			ch4 = currentTime - ch4_start;
			ch4_state = 0;
		}
	}
	
	if(PINC & (1 << PORTC4)) {		//Channel 5
		if(ch5_state == 0) {
			ch5_start = currentTime;
			ch5_state = 1;
		}
	} else if((PINC & (1 << PORTC4)) == 0) {
		if(ch5_state == 1) {
			ch5 = currentTime - ch5_start;
			ch5_state = 0;
		}
	}
	
	if(PINC & (1 << PORTC5)) {		//Channel 6
		if(ch6_state == 0) {
			ch6_start = currentTime;
			ch6_state = 1;
		}
	} else if((PINC & (1 << PORTC5)) == 0) {
		if(ch6_state == 1) {
			ch6 = currentTime - ch6_start;
			ch6_state = 0;
		}
	}
}