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// *************************************************************

// ** Spektrum Diversity - use up to 4 satellite receivers    **

// *************************************************************

// ** Target: An Atmel ATtiny2313 (RC-Oscillator @ 8 MHz)     **

// **         controls a 74HC151 Multiplexer                  **

// *************************************************************

// ** It monitors the data from 4 satellite receivers and     **

// ** connects a valid one to the output via the multiplexer  **

// *************************************************************

// ** LED-Modes during startup (in chronological order)       **

// ** ************************                                **

// ** LED fast blink: Waiting for first datapulse             **

// ** LED slow blink: Waiting 3 seconds while counting sat's  **

// ** LED flashes:    Indicates the number of active sat's    **

// **                                                         **

// ** LED-Modes during operation                              **

// ** **************************                              **

// ** LED OFF: Everything is fine                             **

// ** LED ON:  FAILURE - The first selected sat had lost sync **

// **                                                         **

// ** LED-Modes during Self-Test                              **

// ** **************************                              **

// ** LED flashes at 1 Hz: Everything is fine                 **

// ** LED flashes some times:  FAILURE                        **

// *************************************************************

// ** (c) 2010-0xFFFF Stefan Pendsa                           **

// ** License: don't know - use it and have fun               **

// *************************************************************

#include <avr/io.h>

#include <avr/interrupt.h>

#include <util/delay.h>

#define LED_OFF	PORTD |= 1 << PORTD0

#define LED_ON	PORTD &= ~(1 << PORTD0)

volatile unsigned int TimerEvent;

ISR(TIMER1_OVF_vect)										// Triggered every 8,192 msec

{

	TimerEvent++;

}

void SelectSat(unsigned char sat)

{

	PORTD = (PORTD & 0b00000001) | (sat<<3);				// Select the Input for 74HC151

}

void ResetTimer(void)

{

	TCNT1H = 0;

	TCNT1L = 0;

	TimerEvent = 0;

}

void Binding(void)											// Binding sequence for DX7

{

	unsigned char i = 0;

	DDRB = 0b11110000;										// Sat-Pins to output

	_delay_ms(80);											// Let them boot up

	for (i=0;i<3;i++)										// send three negative 100µs pulses to all sat's

	{

		PORTB = 0b00000000;

		_delay_us(100);

		PORTB = 0b11110000;

		_delay_us(100);

	}

	_delay_ms(1000);

	DDRB = 0b00000000;										// Sat-Pins to input after 1sec

}

void Testing(void)											// Self Test

{

	unsigned char error = 0;

	unsigned char i = 0;

	DDRB = 0b11110000;										// Port B Output for satellites, Input for feedback

	PORTB = 0b01010000;										// Test Pattern

	SelectSat(0);

	if (!(PINB & (1<<PB3))) error++;

	SelectSat(1);

	if (PINB & (1<<PB3)) error++;

	SelectSat(2);

	if (!(PINB & (1<<PB3))) error++;

	SelectSat(3);

	if (PINB & (1<<PB3)) error++;

	PORTB = 0b10100000;										// Another (inverted) Test Pattern

	SelectSat(0);

	if (PINB & (1<<PB3)) error++;

	SelectSat(1);

	if (!(PINB & (1<<PB3))) error++;

	SelectSat(2);

	if (PINB & (1<<PB3)) error++;

	SelectSat(3);

	if (!(PINB & (1<<PB3))) error++;

	DDRB = 0b00000000;										// Port B Input again

	while(1)												// Never return

	{

		if (error == 0)										// When no error occured -> LED flashes at 1 Hz

		{

			LED_ON;

			_delay_ms(100);

			LED_OFF;

			_delay_ms(900);

		}

		else

		{

			for (i=0;i<error;i++)							// When error occured -> Flash once for every error

			{

				LED_ON;

				_delay_ms(100);

				LED_OFF;

				_delay_ms(400);

			}

			_delay_ms(1000);

		}

	}

}

int main(void)

{

	unsigned char i = 0;

	unsigned char j = 0;

	unsigned char active[4];

	unsigned char sat = 4;

	DDRB = 0b00000000;										// Port B Input for satellites and feedback

	DDRD = 0b0011001;										// Port D Output for MUX and LED, Input for Switch & Test

	PORTB = 0b11110000;										// Port B Pullup's for (unused) satellites

	PORTD = 0b1100001;										// Port D Pullup's for Switch & Test, LED on

	for (i=0;i<4;i++) active[i] = 0;						// Reset active-array

	if (!(PIND & (1<<PD5))) Testing();						// Initiate Self-Test when Test-Pad is low

	if (!(PIND & (1<<PD6))) Binding();						// Initiate Binding when Bind-Button is pressed

	TCCR1B = ( 1 << CS10 );									// Timer1 Prescaler = 1 -> 8,192 msec

	TIMSK = ( 1 << TOIE1 );									// Timer1 Overflow Interrupt Enable

	sei();													// Global Interrupts enable

	ResetTimer();

	while((PINB & 0b11110000) == 0b11110000)				// Wait for first signal (SYNC to frame)

	{

		if (TimerEvent == 10) LED_ON;						// Blink while waiting...

		if (TimerEvent == 20)

		{

			LED_OFF;

			TimerEvent = 0;

		}

	}

	LED_OFF;

	ResetTimer();

	while(1)												// Check active satellites for 5 seconds

	{

		if (TimerEvent == 20) LED_ON;						// Blink (slower) while waiting...

		if (TimerEvent == 40)

		{

			LED_OFF;

			TimerEvent = 0;

			j++;

		}

		for (i=0;i<4;i++)

		{

			if (!(PINB & (1<<(i+4))))

			{

				active[i] = 1;

				if (sat == 4)								// Select first active satellite (only once)

				{

					sat = i;

					SelectSat(i);

				}

			}

		}

		if (j == 16) break;									// 16 * 40 * 8ms = ~5sec

	}

	LED_OFF;

	_delay_ms(1000);

	for (i=0;i<4;i++)										// Flash once for every active satellite

	{

		if (active[i] == 1)

		{

			LED_ON;

			_delay_ms(100);

			LED_OFF;

			_delay_ms(400);

		}

	}

	while(1)												// Main-Loop

	{

		for (i=0;i<4;i++) active[i] = 0;					// Reset active-array

		ResetTimer();

		while((PINB & 0b11110000) == 0b11110000)			// Wait for first signal (SYNC to frame)

		{

			if (TimerEvent > 3) break;						// (max. 3*8=24ms)

		}

		ResetTimer();

		while(TimerEvent < 1)								// Check active satellites (for 1*8=8ms)

		{

			for (i=0;i<4;i++)

			{

				if (!(PINB & (1<<(i+4))))

				{

					active[i] = 1;

				}

			}

		}

		if (active[sat] == 0)								// Detect fail on active satellite

		{

			LED_ON;											// Failure-LED ON

			for (i=0;i<4;i++)								// Select lowest active satellite

			{

				if (active[i] == 1)

				{

					sat = i;

					SelectSat(sat);

					break;

				}

			}

		}

		if (!(PIND & (1<<PD6))) LED_OFF;					// Reset Failure-LED when Bind-Button is pressed

	}

}