Initial prototype

This patch adds a skeleton of AVR code for a "simulator" target (atmega2560)
and for the real intended hardware target (atmega32u4). The simulator target
is one that is supported by the QEMU AVR emulator, while the 32u4 is currently
not.

1 files changed, 118 insertions, 0 deletions

diff --git a/display_sim.c b/display_sim.c
new file mode 100644
index 0000000..b17979f
--- /dev/null
+++ b/display_sim.c
@@ -0,0 +1,118 @@
+#include <stdio.h>
+#include <avr/io.h>
+
+#define BAUD 57600
+#include <util/setbaud.h>
+
+#include "display.h"
+
+/* WIDTH+1 for string terminator */
+static char display[LCD_HEIGHT][LCD_WIDTH+1];
+static int cursor_x;
+static int cursor_y;
+
+/* Slightly icky hack to use first avaialable USART */
+#ifdef UDR0
+#  define UBRRx  UBRR0
+#  define UCSRxA UCSR0A
+#  define UCSRxB UCSR0B
+#  define UCSRxC UCSR0C
+#  define UCSZx0 UCSZ00
+#  define UCSZx1 UCSZ01
+#  define RXENx  RXEN0
+#  define TXENx  TXEN0
+#  define UDREx  UDRE0
+#  define UDRx   UDR0
+#  define U2Xx   U2X0
+#else
+#  define UBRRx  UBRR1
+#  define UCSRxA UCSR1A
+#  define UCSRxB UCSR1B
+#  define UCSRxC UCSR1C
+#  define UCSZx0 UCSZ10
+#  define UCSZx1 UCSZ11
+#  define RXENx  RXEN1
+#  define TXENx  TXEN1
+#  define UDREx  UDRE1
+#  define UDRx   UDR1
+#  define U2Xx   U2X1
+#endif
+
+static void uart_init(void)
+{
+	UBRRx = UBRR_VALUE;
+#if USE_2X
+	UCSRxA |= (1 << U2Xx);
+#else
+	UCSRxA &= ~(1 << U2Xx);
+#endif
+    UCSRxB = _BV(RXENx) | _BV(TXENx);
+    UCSRxC = _BV(UCSZx1) | _BV(UCSZx0);
+}
+
+static int uart_putc(char c, FILE *unused)
+{
+	UDRx = c;
+	loop_until_bit_is_set(UCSRxA, UDREx);
+	return 1;
+}
+
+/* uart_out is plopped on stdout so that prints go to it by default */
+static FILE uart_out = FDEV_SETUP_STREAM(uart_putc, NULL, _FDEV_SETUP_WRITE);
+
+/* internal function to dump the display contents to stdout, since there
+ * is no background thread for doing this constantly */
+void display_display(void)
+{
+	int x = 0;
+	int y = 0;
+	printf("\033[6A"); // hack: raw ANSI escape sequence to move up 6
+	printf(",--------------------.\n");
+	for (y = 0; y < LCD_HEIGHT; y++) {
+		printf("|%s|\n", display[y]);
+	}
+	printf("`--------------------'\n");
+}
+
+void display_clear(void)
+{
+	int x = 0;
+	int y = 0;
+	for (y = 0; y < LCD_HEIGHT; y++) {
+		for (x = 0; x < LCD_WIDTH; x++) {
+			display[y][x] = ' ';
+		}
+		display[y][x] = '\0';
+	}
+
+	display_display();
+}
+
+void display_init(void)
+{
+	uart_init();
+	/* FIXME hack: stdout not guaranteed to be assignable */
+	stdout = &uart_out;
+	display_clear();
+	cursor_x = cursor_y = 0;
+}
+
+void display_write(const char *text)
+{
+	size_t text_x = 0;
+	char c = '\0';
+	while (cursor_x < LCD_WIDTH && *text) {
+		c = *(text++);
+		/* 0-7 are custom chars in CGRAM on real LCD */
+		if (c < 8)
+			c = '_';
+		display[cursor_y][cursor_x++] = c;
+	}
+	display_display();
+}
+
+void display_set_cursor(int x, int y)
+{
+	cursor_x = x;
+	cursor_y = y;
+}