altos/stm-vga: Implement VGA out from the STM processor

Generates vsync/hsync using timers and pixel data using the SPI port.
320x240 video using 640x480 mode and a 24MHz "pixel" clock.
Includes the beginings of rendering code for the frame buffer,
including bitblt, solid fill and text with a 5x7 font.

Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/src/draw/ao_text.c b/src/draw/ao_text.c
new file mode 100644
index 00000000..68d6c2cf
--- /dev/null
+++ b/src/draw/ao_text.c
@@ -0,0 +1,44 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao.h"
+#include "ao_draw.h"
+#include "ao_font.h"
+
+void
+ao_text(char		*string,
+	uint32_t	*dst_line,
+	int16_t		dst_stride,
+	int16_t		dst_x)
+{
+	char		c;
+	uint32_t	src[GLYPH_HEIGHT];
+
+	while ((c = *string++)) {
+		uint8_t	*bytes = &glyph_bytes[glyph_pos[(uint8_t) c]];
+		int	h;
+
+		for (h = 0; h < GLYPH_HEIGHT; h++)
+			src[h] = bytes[h];
+
+		ao_blt(src, 1, 0,
+		       dst_line, dst_stride,
+		       dst_x,
+		       GLYPH_WIDTH,
+		       GLYPH_HEIGHT,
+		       AO_AND_INVERTED,
+		       0, 0);
+		dst_x += GLYPH_WIDTH;
+	}
+}