1 files changed, 123 insertions, 0 deletions
diff --git a/avr/serial.c b/avr/serial.c
new file mode 100644
index 0000000..b2fea51
--- /dev/null
+++ b/avr/serial.c
@@ -0,0 +1,123 @@
+/*
+ */
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <util/atomic.h>
+#include <errno.h>
+#include <stdio.h>
+
+#include "ring.h"
+#include "serial.h"
+
+
+static int _write(char c, FILE *stream);
+static FILE mystdout = FDEV_SETUP_STREAM(_write, 
+		NULL, _FDEV_SETUP_WRITE);
+
+
+
+#define BUFFER_SIZE 64
+
+#if ((BUFFER_SIZE-1) & BUFFER_SIZE)
+# error: BUFFER_SIZE not power of 2
+#endif
+
+#if ((BUFFER_SIZE) > 256)
+# error: BUFFER_SIZE 
+#endif
+
+struct ring rx_ring;
+struct ring tx_ring;
+uint8_t rx_ring_buffer[BUFFER_SIZE];
+uint8_t tx_ring_buffer[BUFFER_SIZE];
+
+
+
+/* Initialize UART */
+
+void usart0_setup(void) {
+
+	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+
+		PRR0 &= ~_BV(PRUSART0);
+		UCSR0B = 0;
+
+		/* Initialize ring buffers. */
+		ring_init(&rx_ring, rx_ring_buffer, BUFFER_SIZE);
+		ring_init(&tx_ring, tx_ring_buffer, BUFFER_SIZE);
+
+		UCSR0A = 0;
+		UBRR0  = F_CPU / BAUD / 16 - 1;
+		UCSR0B = _BV(RXCIE0) | _BV(RXEN0) | _BV(TXEN0);
+		UCSR0C = 3 << UCSZ00;
+	};
+}
+
+/*--------------------------------------------------------------------------*/
+
+/* UART RXC interrupt */
+
+ISR(USART0_RX_vect)
+{
+	uint8_t d;
+
+	d = UDR0;
+	ring_write_ch(&rx_ring, d);
+}
+
+/* UART UDRE interrupt */
+
+ISR(USART0_UDRE_vect)
+{
+	int d = ring_read_ch(&tx_ring);
+
+	if (d < 0) {
+		/* Disable TX empty interrupt. */
+		UCSR0B = _BV(RXCIE0) | _BV(RXEN0) | _BV(TXEN0);
+	} else {
+		UDR0 = d;
+	}
+}
+
+/*--------------------------------------------------------------------------*/
+
+void serial_setup(void)
+{
+	stdout = &mystdout;
+	usart0_setup();
+}
+
+/*--------------------------------------------------------------------------*/
+
+int _write(char c, FILE *stream)
+{
+	(void) stream;
+
+	if (c == '\n')
+		serial_putc('\r');
+	serial_putc(c);
+
+	return 0;
+}
+
+int serial_getc(void)
+{
+	return ring_read_ch(&rx_ring);
+}
+
+void serial_putc(char data)
+{
+	while (ring_write_ch(&tx_ring, data) < 0)
+		;
+
+	/* Enable the TXE interrupt. */
+	UCSR0B = _BV(RXCIE0) | _BV(RXEN0) | _BV(TXEN0) | _BV(UDRIE0);
+}
+
+uint_fast8_t serial_tstc(void)
+{
+	return !ring_is_empty(&rx_ring);
+}
+
+