Basic motor control using an RC receiver with a Baby Orangutan robot controller

gistfile1.c

#include <pololu/orangutan.h>

#define RIGHT_STICK_V 0
#define RIGHT_STICK_V_MIN 3000
#define RIGHT_STICK_V_MAX 4500

#define LEFT_STICK_V 1
#define LEFT_STICK_V_MIN 3000
#define LEFT_STICK_V_MAX 4500

#define RIGHT_STICK_H 2
#define RIGHT_STICK_H_MIN 2675
#define RIGHT_STICK_H_MAX 4350

// Re-maps a number from one range to another.
// Taken from http://arduino.cc/en/reference/map
long map(long x, long in_min, long in_max, long out_min, long out_max) {
	return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

// Constrains a number to be within a range
long constrain(long x, long min, long max) {
	if (x < min) return min; 
	if (x > max) return max;
	return x;
}

int main() {
	// Set PD2, PD4 & PD7 as PWM inputs for the RC receiver
	pulse_in_start((unsigned char[]) {IO_D2, IO_D4, IO_D7}, 3);
	
	unsigned long pulse_width;
	int speed;
	
	while(1) {
		// Get the pulse width for the left stick vertical position and make
		// sure it's within the specified range
		pulse_width = get_last_high_pulse(LEFT_STICK_V);
		pulse_width = constrain(pulse_width, LEFT_STICK_V_MIN, LEFT_STICK_V_MAX);
		
		// Map the pulse width to the speed value (between -255 and 255)
		speed = map(pulse_width, LEFT_STICK_V_MIN, LEFT_STICK_V_MAX, -255, 255);
		
		// Set the first motor speed
		set_m1_speed(speed);
	}
}