docs: updated @param tags, added missing function descriptions, other minor changes

Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

src/relay/relay.h

@@ -48,16 +48,46 @@ typedef struct _relay_context{
     mraa_gpio_context gpio;
 } *relay_context;
 
+/**
+ * relay init function
+ *
+ * @param pin Pin to use
+ */
 relay_context relay_init(int pin);
 
+/**
+ * relay destructor
+ */
 void relay_close(relay_context dev);
 
+/**
+ * Sets the relay switch to on (closed circuit). This allows current
+ * to flow and lights up the indicator LED.
+ *
+ * @return result of the operation
+ */
 upm_result_t relay_on(relay_context dev);
 
+/**
+ * Sets the relay switch to off (open circuit). This stops current
+ * from flowing and the indicator LED is not lit.
+ *
+ * @return result of the operation
+ */
 upm_result_t relay_off(relay_context dev);
 
+/**
+ * Checks whether the relay switch is closed.
+ *
+ * @return True if the switch is on (closed), false otherwise
+ */
 bool relay_is_on(relay_context dev);
 
+/**
+ * Checks whether the relay switch is open.
+ *
+ * @return True if the switch is off (open), false otherwise
+ */
 bool relay_is_off(relay_context dev);
 
 #endif /* RELAY_H_ */

src/relay/relay.hpp

@@ -62,7 +62,7 @@ namespace upm {
         /**
          * relay constructor
          *
-         * @param gpio Pin to use
+         * @param pin Pin to use
          */
         Relay(unsigned int pin);
         /**