move display and system into separate files

1 files changed, 64 insertions, 0 deletions

diff --git a/src/display.cc b/src/display.cc
new file mode 100644
index 0000000..e06f271
--- /dev/null
+++ b/src/display.cc
@@ -0,0 +1,64 @@
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <avr/wdt.h>
+#include <util/delay.h>
+#include <stdlib.h>
+
+#include "display.h"
+
+Display display;
+
+extern volatile uint8_t disp[8];
+
+void Display::turn_off()
+{
+	TIMSK0 &= ~_BV(TOIE0);
+	PORTB = 0;
+	PORTD = 0;
+}
+
+void Display::turn_on()
+{
+	TIMSK0 |= _BV(TOIE0);
+}
+
+/*
+ * Draws a single display column. This function should be called at least once
+ * per millisecond.
+ *
+ * Current configuration:
+ * Called every 256 microseconds. The whole display is refreshed every 2048us,
+ * giving a refresh rate of ~500Hz
+ */
+ISR(TIMER0_OVF_vect)
+{
+	static uint8_t active_col = 0;
+	static uint16_t scroll = 0;
+	static uint8_t disp_offset = 0;
+
+	static uint8_t disp_buf[8];
+
+	uint8_t i;
+
+	if (++scroll == 512) {
+		scroll = 0;
+		if (++disp_offset == sizeof(disp)) {
+			disp_offset = 0;
+		}
+
+		for (i = 0; i < 8; i++) {
+			disp_buf[i] = ~disp[(disp_offset + i) % sizeof(disp)];
+		}
+	}
+
+	/*
+	 * To avoid flickering, do not put any code (or expensive index
+	 * calculations) between the following three lines.
+	 */
+	PORTB = 0;
+	PORTD = disp_buf[active_col];
+	PORTB = _BV(active_col);
+
+	if (++active_col == 8)
+		active_col = 0;
+}