add preliminary arduino nano dmx driver

note that it disables stdout / kout support, as the ATMega328 only has one
UART.

include/arch/arduino-nano/driver/dmx.h

+/*
+ * Copyright 2022 Daniel Friesel
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+class DMX {
+	private:
+		DMX(const DMX &copy);
+
+	public:
+		unsigned char frames[16];
+
+		DMX() {}
+
+		void setup();
+		void write();
+};
+
+extern DMX dmx;

src/arch/arduino-nano/Kconfig

@@ -35,6 +35,15 @@ config arch_arduino_nano_driver_timer
 bool "Timer with Interrupts"
 select meta_driver_timer
 
+config arch_arduino_nano_driver_dmx
+bool "DMX"
+select meta_driver_dmx
+
+config arch_arduino_nano_driver_dmx_pin
+string "DMX Pin"
+default "pb5"
+depends on arch_arduino_nano_driver_dmx
+
 choice arch_arduino_nano_cpu
 bool "CPU Type"
 

src/arch/arduino-nano/Makefile.inc

@@ -88,6 +88,10 @@ ifdef CONFIG_arch_arduino_nano_driver_adc
 	CXX_TARGETS += src/arch/arduino-nano/driver/adc.cc
 endif
 
+ifdef CONFIG_arch_arduino_nano_driver_dmx
+	CXX_TARGETS += src/arch/arduino-nano/driver/dmx.cc
+endif
+
 ifdef CONFIG_arch_arduino_nano_driver_spi
 	CXX_TARGETS += src/arch/arduino-nano/driver/spi.cc
 endif

src/arch/arduino-nano/driver/dmx.cc

+/*
+ * 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"
+
+#define BAUD 250000UL
+#include <util/setbaud.h>
+
+void DMX::setup()
+{
+	UBRR0H = UBRRH_VALUE;
+	UBRR0L = UBRRL_VALUE;
+
+#if USE_2X
+	UCSR0A |= _BV(U2X0);
+#else
+	UCSR0A &= ~_BV(U2X0);
+#endif
+
+	UCSR0B |= _BV(TXEN0);
+	UCSR0C = _BV(USBS0) | _BV(UCSZ01) | _BV(UCSZ00); // 8 bits
+}
+
+void DMX::write()
+{
+	// Disable UART for reset and mark signals
+	UCSR0B &= ~_BV(TXEN0);
+	gpio.output(GPIO::pd1, 0);
+	arch.delay_us(88); // break
+	gpio.output(GPIO::pd1, 1);
+	arch.delay_us(8);
+	UCSR0B |= _BV(TXEN0); // causes line to go high
+	for (uint8_t i = 0; i < 16; i++) {
+		while (!(UCSR0A & _BV(UDRE0)));
+		UDR0 = frames[i];
+	}
+	for (uint8_t i = 0; i < 241; i++) {
+		while (!(UCSR0A & _BV(UDRE0)));
+		UDR0 = 0;
+	}
+	for (uint8_t i = 0; i < 255; i++) {
+		while (!(UCSR0A & _BV(UDRE0)));
+		UDR0 = 0;
+	}
+}
+
+DMX dmx;

src/driver/Kconfig

@@ -6,6 +6,8 @@ config meta_driver_adc
 bool
 config meta_driver_counter
 bool
+config meta_driver_dmx
+bool
 config meta_driver_hardware_i2c
 bool
 config meta_driver_i2c