atmega2560: add dmx driver on UART3

/*

 * Copyright 2022 Daniel Friesel

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

class DMX {

	private:

		DMX(const DMX &copy);

	public:

		static unsigned char const num_frames = 32;

		unsigned char frames[num_frames];

		DMX() {}

		void setup();

		void write();

};

extern DMX dmx;

/*

 * Copyright 2022 Daniel Friesel

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#include <avr/io.h>

#include "arch.h"

#include "driver/dmx.h"

#include "driver/gpio.h"

#undef BAUD

#define BAUD 250000UL

#include <util/setbaud.h>

void DMX::setup()

{

	UBRR3H = UBRRH_VALUE;

	UBRR3L = UBRRL_VALUE;

#if USE_2X

	UCSR3A |= _BV(U2X3);

#else

	UCSR3A &= ~_BV(U2X3);

#endif

	UCSR3B = _BV(TXEN3);

	UCSR3C = _BV(USBS3) | _BV(UCSZ31) | _BV(UCSZ30); // MSB first, 8 data bits, 2 stop bits, no parity

}

void DMX::write()

{

	// Disable UART for reset and mark signals

	UCSR3B &= ~_BV(TXEN3);

	gpio.output(GPIO::pj1, 0);

	arch.delay_us(88); // break / reset

	gpio.output(GPIO::pj1, 1);

	arch.delay_us(8); // mark

	UCSR3B |= _BV(TXEN3); // causes line to go high

	for (uint8_t i = 0; i < 32; i++) {

		while (!(UCSR3A & _BV(UDRE3)));

		UDR3 = frames[i];

	}

	for (uint8_t i = 0; i < 258 - num_frames; i++) {

		while (!(UCSR3A & _BV(UDRE3)));

		UDR3 = 0;

	}

	for (uint8_t i = 0; i < 255; i++) {

		while (!(UCSR3A & _BV(UDRE3)));

		UDR3 = 0;

	}

}

DMX dmx;