+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* key matrix position */
+typedef struct {
+ uint8_t col;
+ uint8_t row;
+} key_t;
+
+/* key event */
+typedef struct {
+ key_t key;
+ bool pressed;
+ uint16_t time;
+} keyevent_t;
+
+/* equivalent test of key_t */
+#define KEYEQ(keya, keyb) ((keya).row == (keyb).row && (keya).col == (keyb).col)
+
+/* (time == 0) means no event and assumes matrix has no 255 line. */
+#define IS_NOEVENT(event) ((event).time == 0 || ((event).key.row == 255 && (event).key.col == 255))
+
+#define NOEVENT (keyevent_t){ \
+ .key = (key_t){ .row = 255, .col = 255 }, \
+ .pressed = false, \
+ .time = 0 \
+}
+
+/* tick event */
+#define TICK (keyevent_t){ \
+ .key = (key_t){ .row = 255, .col = 255 }, \
+ .pressed = false, \
+ .time = (timer_read() | 1) \
+}
+
+