Add doxygen comments

src/display.c

@@ -175,6 +175,7 @@ int display_set_message(char* msg) {
 }
 
 int display_set_time(int time) {
+	lv_label_set_text_fmt(display_clock_label, "%d:%d", time / 100, time % 100)
 	return 0;
 }
 

src/display.h

@@ -1,22 +1,73 @@
 #ifndef DISPLAY_H
 #define DISPLAY_H
 
+/**
+ * @brief Initializes all display elements and adds them to the canvas.
+ *
+ * @return int
+ */
 int init_display();
 
+/**
+ * @brief Updates all information on the display using the get functions, defined by `display.c`. Alternatively the
+ * values of the displayed elements can be set explicitly via set `display_set_<property>`-functions.
+ *
+ * @return int
+ */
 int update_display();
 
+/**
+ * @brief This is the entry point for the display thread. It peridocially updates the display and handles input events.
+ *
+ */
 void display_thread(void*, void*, void*);
 
+/**
+ * @brief Displays a message at the bottom of the display. The message will persist until it is removed expicitly, by calling `display_set_message("")`.
+ * 
+ * @param msg A pointer to the string that should be displayed
+ * @return int 
+ */
 int display_set_message(char* msg);
 
+/**
+ * @brief Sets the on display clock. The time should have the format `h * 100 + m`. So `display_set_time(1145)` sets the clock to 11:45.
+ * 
+ * @param time A number representation of the time
+ * @return int 
+ */
 int display_set_time(int time);
 
+/**
+ * @brief Set the battery level percentage.
+ * 
+ * @param bat The battery level in percent
+ * @return int 
+ */
 int display_set_bat(int bat);
 
+/**
+ * @brief Set the non-volatile memory state.
+ * 
+ * @param mem The occupied memory in percent
+ * @return int 
+ */
 int display_set_mem(int mem);
 
+/**
+ * @brief Set the number of total registered contacts in the last 14 days.
+ * 
+ * @param contacts The number of contacts
+ * @return int 
+ */
 int display_set_contacts(int contacts);
 
+/**
+ * @brief Set the number of contacts that were tested positively on Covid and registered in the last 14 days.
+ * 
+ * @param risk_contacts The number of risk contacts
+ * @return int 
+ */
 int display_set_risk_contacts(int risk_contacts);
 
 #endif