/elec/quadcopter

//

// main.ino

//

// This software is intended to be run on a small Arduino (e.g., a Pro Mini),

// whose purpose is dedicated to talking to the RC system.  That is to say, it

// listens to the PPM signal from the RC receiver and produces a compatible

// single for the ESCs to control the motors.  It additionally talks to the main

// board via a trivial serial protocol.  In so doing, this software relieves the

// main board (and software running on it) of the task of interfacing with any

// of the RC system.

//

// Receiver

// --------

//

// The 8 channels (from the RC receiver) need to be combined and fed to two

// interrupts on the Arduino.  They need to be combined in such a way as to

// alternate pulses between the two interrupts (which are alternately used to

// read the pulses).  Like this:

//

//                  ch1  ch3  ch5  ch7  ch2  ch4  ch6  ch8

//                   |    |    |    |    |    |    |    |

//                   ▼    ▼    ▼    ▼    ▼    ▼    ▼    ▼

//                   ¯    ¯    ¯    ¯    ¯    ¯    ¯    ¯

//            ___    |    |    |    |    |    |    |    |     ___

//    GND ---|___|---+----+----+----+    +----+----+----+----|___|--- GND

//             R                    |    |                     R

//         ________________________ | __ | _____________________

//         ARDUINO                  |    |

//                           pin 2  o    o  pin 3

//                    (interrupt 0)        (interrupt 1)

//

// The two resistors in the circuit are pull-down resistors (so, say 100kΩ).

// Without them, the Arduino is unable to read the pulse wave at all.

//

// Note that your receiver may not send pulses sequentially, in "channel order".

// If this turns out to be the case, you will need to arrange for the pulses to

// wire up the channels in an order whereby the pulses arrive alternately

// between the two interrupts and adjust the channel order in config.h.

//

// Motor control

// -------------

//

// The four motor control outputs should be fed directly to the ESCs.

//

//                            ESC  ESC  ESC  ESC

//                             o    o    o    o

//                             |    |    |    |

//         ___________________ | __ | __ | __ | _____

//         ARDUINO             |    |    |    |

//                      pin 4  o    o    o    o  pin 7

//

// SERIAL INTERFACE

// ----------------

//

// The serial interface (pins 0 and 1) talk a very simple protocol.  When a

// complete set of 8 channel values have been read, it writes 0xffff followed by

// the 8, 16-bit unsigned channel values.  It expects to recieve 0xffff,

// followed by 4, 16-bit unsigned channel values.  All channel values are in the

// range specified in config.h.

#include "config.h"

#include "receiver.h"

#include "motors.h"

#include "comms.h"

void flash_led()

{

	static bool on = false;

	on = !on;

	digitalWrite( LED_PIN, on? HIGH : LOW );

}

void setup()

{

	// init subsystems

	Receiver::setup();

	Motors::setup();

	Comms::setup();

	// led

	pinMode( LED_PIN, OUTPUT );

	digitalWrite( LED_PIN, LOW );

}

void loop()

{

	int motor_values[ NUM_MOTORS ];

	int channel_values[ NUM_CHANNELS ];

	// reset the motor values

	for( int a = 0; a < NUM_MOTORS; a++ )

		motor_values[ a ] = 0;

	while( true )

	{

		// have we read a whole set of channel values?

		if( Receiver::read_channels( channel_values ) )

		{

			// yes, flash led!

			flash_led();

			// send channel values to main board

			Comms::write_channels( channel_values );

		}

		// update motors

		Motors::update();

		// read channel values from main board

		if( Comms::read_channels( motor_values ) )

		{

			// set motor speeds

			Motors::set_values( motor_values );

		}

		// update motors

		Motors::update();

	}

}