atmega2560: add dmx driver on UART3

2 files changed, 74 insertions, 0 deletions

diff --git a/include/arch/atmega2560/driver/dmx.h b/include/arch/atmega2560/driver/dmx.h
new file mode 100644
index 0000000..5550c19
--- /dev/null
+++ b/include/arch/atmega2560/driver/dmx.h
@@ -0,0 +1,21 @@
+/*
+ * 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;
diff --git a/src/arch/atmega2560/driver/dmx.cc b/src/arch/atmega2560/driver/dmx.cc
new file mode 100644
index 0000000..1b21aea
--- /dev/null
+++ b/src/arch/atmega2560/driver/dmx.cc
@@ -0,0 +1,53 @@
+/*
+ * 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;