1 files changed, 72 insertions, 0 deletions
diff --git a/bridge.c b/bridge.c
new file mode 100644
index 0000000..5f1806b
--- /dev/null
+++ b/bridge.c
@@ -0,0 +1,72 @@
+#include <avr/io.h>
+#include <util/delay.h>
+
+#include "bridge.h"
+
+/* port D
+ *
+ *  4 1- (NMOS, inverted) 
+ *  5 1+ (PMOS)
+ *  6 2- (NMOS, inverted)
+ *  7 2+ (PMOS)
+ *
+ */
+
+#define D_1_MINUS	(1 << 4)
+#define D_1_PLUS	(1 << 5)
+#define D_2_MINUS	(1 << 6)
+#define D_2_PLUS	(1 << 7)
+
+enum bridge_state {
+	BRIDGE_OFF,
+	BRIDGE_HEATING,
+	BRIDGE_COOLING
+};
+
+static enum bridge_state bridge_state;
+
+/* Turns the H-bridge off, putting the output
+ * into high impedance mode. */
+void bridge_off(void)
+{
+	if (bridge_state == BRIDGE_OFF)
+		return;
+
+	PORTD |= D_1_MINUS | D_2_MINUS;
+	PORTD &= ~(D_1_PLUS | D_2_PLUS);
+	_delay_ms(100);
+	bridge_state = BRIDGE_OFF;
+}
+
+/* Turns the H-bridge on, setting 1+ 2- */
+void bridge_on_heat(void)
+{
+	if (bridge_state == BRIDGE_HEATING)
+		return;
+
+	bridge_off();
+	bridge_state = BRIDGE_HEATING;
+	PORTD |= D_1_PLUS;
+	PORTD &= ~D_2_MINUS;
+}
+
+/* Turns the H-bridge on, setting 1- 2+ */
+void bridge_on_cool(void)
+{
+	if (bridge_state == BRIDGE_COOLING)
+		return;
+
+	bridge_off();
+	bridge_state = BRIDGE_COOLING;
+	PORTD |= D_2_PLUS;
+	PORTD &= ~D_1_MINUS;
+}
+
+/* Initializes the output port needed for the H-bridge */
+void bridge_init(void)
+{
+	PORTD |= D_1_MINUS | D_2_MINUS;
+	PORTD &= ~(D_1_PLUS | D_2_PLUS);
+	DDRD |= D_1_PLUS | D_1_MINUS | D_2_PLUS | D_2_MINUS;
+	bridge_state = BRIDGE_OFF;
+}