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//
// 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();
}
}
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