examples: added missing snippets and paired them with right examples

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

src/grove/grove.h

@@ -58,6 +58,7 @@ class Grove {
  *
  * @ingroup grove gpio
  * @snippet groveled.cxx Interesting
+ * @snippet groveled-multi.cxx Interesting
  */
 class GroveLed: public Grove {
     public:

src/maxds3231m/maxds3231m.h

@@ -71,6 +71,7 @@ struct Time3231 {
  * @brief C++ API for MAXDS3231M chip (Ambient and Infrared Proximity Sensor)
  *
  * @ingroup maxds3231m i2c
+ * @snippet maxds3231m.cxx Interesting
  */
 class MAXDS3231M {
     public:

src/my9221/my9221.h

@@ -49,6 +49,7 @@ namespace upm {
  *
  * @ingroup my9221 gpio
  * @snippet my9221-ledbar.cxx Interesting
+ * @snippet my9221-updown.cxx Interesting
  */
 class MY9221 {
     public:

src/nrf24l01/nrf24l01.h

@@ -163,6 +163,7 @@ typedef enum {
  * @ingroup nrf24l01
  * @snippet nrf24l01-receiver.cxx Interesting
  * @snippet nrf24l01-transmitter.cxx Interesting
+ * @snippet nrf24l01-broadcast.cxx Interesting
  */
 class NRF24L01 {
     public:

src/nrf8001/nrf8001.h

@@ -31,5 +31,23 @@
 #include <lib_aci.h>
 #include <aci_setup.h>
 
+/**
+ * @brief nrf8001 Bluetooth Low Energy library
+ * @defgroup nrf8001 libupm-nrf8001
+ */
+
+/**
+ * @brief C++ API for the Nordic Semiconductor NRF8001 Bluetooth Low Energy
+ *
+ * This file defines the NRF8001 C++ interface for lib-nrf8001.
+ * Most of the interaction with this device is done using the ACI classes
+ * provided by Nordic Semiconductor. Please see our examples for further
+ * details.
+ *
+ * @ingroup nrf8001 spi
+ * @snippet nrf8001-helloworld.cxx Interesting
+ * @snippet nrf8001-broadcast.cxx Interesting
+ */
+
 void init_local_interfaces (aci_state_t* aci, uint8_t reqn, uint8_t rdyn, uint8_t rst);
 void close_local_interfaces (aci_state_t* aci);

src/pulsensor/pulsensor.h

@@ -39,6 +39,24 @@
 #define TRUE               HIGH
 #define FALSE              LOW
 
+
+/**
+ * @brief pulsensor pulse sensor library
+ * @defgroup pulsensor libupm-pulsensor
+ */
+
+/**
+ * @brief C++ API for 3-wire pulse sensor
+ *
+ * This is a library for the 3-wire pulse sensor sold by several manufacturers.
+ * Usually, you can identify the sensor based on the round breakout and the
+ * distinctive heart symbol. 
+ *
+ * @ingroup pulsensor analog
+ * @snippet pulsensor.cxx Interesting
+ */
+
+
 /*!
  * @struct clbk_data
  * @brief callback data