Document apps in doxygen module style, create more top-level categories to structure documentation

src/apps/sntp/sntp.c

@@ -1,17 +1,6 @@
 /**
  * @file
  * SNTP client module
- *
- * This is simple "SNTP" client for the lwIP raw API.
- * It is a minimal implementation of SNTPv4 as specified in RFC 4330.
- *
- * For a list of some public NTP servers, see this link :
- * http://support.ntp.org/bin/view/Servers/NTPPoolServers
- *
- * @todo:
- * - set/change servers at runtime
- * - complete SNTP_CHECK_RESPONSE checks 3 and 4
- * - support broadcast/multicast mode?
  */
 
 /*
@@ -45,6 +34,22 @@
  * Author: Frédéric Bernon, Simon Goldschmidt
  */
 
+
+/**
+ * @defgroup sntp SNTP
+ * @ingroup apps
+ *
+ * This is simple "SNTP" client for the lwIP raw API.
+ * It is a minimal implementation of SNTPv4 as specified in RFC 4330.
+ *
+ * For a list of some public NTP servers, see this link :
+ * http://support.ntp.org/bin/view/Servers/NTPPoolServers
+ *
+ * @todo:
+ * - set/change servers at runtime
+ * - complete SNTP_CHECK_RESPONSE checks 3 and 4
+ */
+
 #include "lwip/apps/sntp.h"
 
 #include "lwip/opt.h"
@@ -523,6 +528,7 @@ sntp_request(void *arg)
 }
 
 /**
+ * @ingroup sntp
  * Initialize this module.
  * Send out request instantly or after SNTP_STARTUP_DELAY(_FUNC).
  */
@@ -559,6 +565,7 @@ sntp_init(void)
 }
 
 /**
+ * @ingroup sntp
  * Stop this module.
  */
 void
@@ -572,6 +579,7 @@ sntp_stop(void)
 }
 
 /**
+ * @ingroup sntp
  * Get enabled state.
  */
 u8_t sntp_enabled(void)
@@ -580,6 +588,7 @@ u8_t sntp_enabled(void)
 }
 
 /**
+ * @ingroup sntp
  * Sets the operating mode.
  * @param operating_mode one of the available operating modes
  */
@@ -592,6 +601,7 @@ sntp_setoperatingmode(u8_t operating_mode)
 }
 
 /**
+ * @ingroup sntp
  * Gets the operating mode.
  */
 u8_t
@@ -616,6 +626,7 @@ sntp_servermode_dhcp(int set_servers_from_dhcp)
 #endif /* SNTP_GET_SERVERS_FROM_DHCP */
 
 /**
+ * @ingroup sntp
  * Initialize one of the NTP servers by IP address
  *
  * @param idx the index of the NTP server to set must be < SNTP_MAX_SERVERS
@@ -664,6 +675,7 @@ dhcp_set_ntp_servers(u8_t num, const ip4_addr_t *server)
 #endif /* LWIP_DHCP && SNTP_GET_SERVERS_FROM_DHCP */
 
 /**
+ * @ingroup sntp
  * Obtain one of the currently configured by IP address (or DHCP) NTP servers
  *
  * @param idx the index of the NTP server