diff --git a/include/villas/nodes/websocket.h b/include/villas/nodes/websocket.h
index a19cb65f7..707cf2538 100644
--- a/include/villas/nodes/websocket.h
+++ b/include/villas/nodes/websocket.h
@@ -36,7 +36,7 @@ struct websocket {
 	struct list destinations;		/**< List of websocket servers connect to in client mode (struct websocket_destination). */
 	
 	struct pool pool;
-	struct queue_signalled queue;   /**< For samples which are received from WebSockets a */
+	struct queue_signalled queue;   /**< For samples which are received from WebSockets */
 };
 
 /* Internal datastructures */
diff --git a/include/villas/sample.h b/include/villas/sample.h
index acae32eed..392abf3da 100644
--- a/include/villas/sample.h
+++ b/include/villas/sample.h
@@ -32,19 +32,19 @@ enum sample_data_format {
 };
 
 struct sample {
-	int sequence;		/**< The sequence number of this sample. */
-	int length;		/**< The number of values in sample::values which are valid. */
-	int capacity;		/**< The number of values in sample::values for which memory is reserved. */
+	int sequence; /**< The sequence number of this sample. */
+	int length;   /**< The number of values in sample::values which are valid. */
+	int capacity; /**< The number of values in sample::values for which memory is reserved. */
 	
-	atomic_int refcnt;	/**< Reference counter. */
-	off_t pool_off;	/**< This sample is belong to this memory pool (relative pointer). */
-	struct node *source;	/**< The node from which this sample originates. */
+	atomic_int refcnt;   /**< Reference counter. */
+	off_t pool_off;	     /**< This sample belongs to this memory pool (relative pointer). */
+	struct node *source; /**< The node from which this sample originates. */
 
 	/** All timestamps are seconds / nano seconds after 1.1.1970 UTC */
 	struct {
 		struct timespec origin;		/**< The point in time when this data was sampled. */
 		struct timespec received;	/**< The point in time when this data was received. */
-		struct timespec sent;		/**< The point in time this data was send for the last time. */
+		struct timespec sent;		/**< The point in time when this data was send for the last time. */
 	} ts;
 	
 	uint64_t format;	/**< A long bitfield indicating the number representation of the first 64 values in sample::data[] */
@@ -70,8 +70,8 @@ int sample_get(struct sample *s);
 /** Decrease reference count and release memory if last reference was held. */
 int sample_put(struct sample *s);
 
-/** Set number representation for a single value of a sample. */
+/** Get number representation for a single value of a sample. */
 int sample_get_data_format(struct sample *s, int idx);
 
-/** Get number representation for a single value of a sample. */
+/** Set number representation for a single value of a sample. */
 int sample_set_data_format(struct sample *s, int idx, enum sample_data_format fmt);
diff --git a/include/villas/sample_io.h b/include/villas/sample_io.h
index 12acc46d6..20e2d76ee 100644
--- a/include/villas/sample_io.h
+++ b/include/villas/sample_io.h
@@ -71,6 +71,3 @@ int sample_io_villas_scan(const char *line, struct sample *s, int *fl);
 int sample_io_villas_fprint(FILE *f, struct sample *s, int flags);
 
 int sample_io_villas_fscan(FILE *f, struct sample *s, int *flags);
-
-/* JSON format */
-
diff --git a/include/villas/shmem.h b/include/villas/shmem.h
index 7725cae4d..ce88a9fa8 100644
--- a/include/villas/shmem.h
+++ b/include/villas/shmem.h
@@ -11,6 +11,7 @@
 #include "queue.h"
 #include "queue_signalled.h"
 
+/** A signalled queue or a regular (polling) queue, depending on the polling setting. */
 union shmem_queue {
 	struct queue q;
 	struct queue_signalled qs;
@@ -18,27 +19,50 @@ union shmem_queue {
 
 /** The structure that actually resides in the shared memory. */
 struct shmem_shared {
-	size_t len;		/**< Total size of the shared memory region.*/
+	size_t len;                       /**< Total size of the shared memory region.*/
 
-	int polling;		/**< Whether to use a pthread_cond_t to signal if new samples are written to incoming queue. */
+	int polling;                      /**< Whether to use a pthread_cond_t to signal if new samples are written to incoming queue. */
 
-	union shmem_queue in;	/**< Queue for samples passed from external program to node.*/
-	union shmem_queue out;	/**< Queue for samples passed from node to external program.*/
+	union shmem_queue in;             /**< Queue for samples passed from external program to node.*/
+	union shmem_queue out;            /**< Queue for samples passed from node to external program.*/
 
-	struct pool pool;	/**< Pool for the samples in the queues. */
+	struct pool pool;                 /**< Pool for the samples in the queues. */
 
-	pthread_barrier_t start_bar;
+	pthread_barrier_t start_bar;      /**< Barrier for synchronizing the start of both programs. */
 	pthread_barrierattr_t start_attr;
-	atomic_size_t node_stopped;
-	atomic_size_t ext_stopped;
+	atomic_size_t node_stopped;       /**< Set to 1 by VILLASNode if it is stopped/killed. */
+	atomic_size_t ext_stopped;        /**< Set to 1 by the external program if it is stopped/killed. */
 };
 
+/** Open the shared memory object and retrieve / initialize the shared data structures.
+ * @param[in] name Name of the POSIX shared memory object.
+ * @param[inout] base_ptr The base address of the shared memory region is written to this pointer.
+ * @retval A valid shmem_shared* on success, or NULL with errno indicating the error on failure.
+ */
 struct shmem_shared * shmem_shared_open(const char* name, void **base_ptr);
 
+/** Close and destroy the shared memory object and related structures.
+ * @param[shm] The shared memory structure.
+ * @param[base] The base address as returned by shmem_shared_open.
+ */
 int shmem_shared_close(struct shmem_shared *shm, void *base);
 
+/** Read samples from VILLASNode.
+ * @param[shm] The shared memory structure.
+ * @param[smps] An array where the pointers to the samples will be written. The samples
+ * must be freed with sample_put after use.
+ * @param[cnt] Number of samples to be read.
+ */
 int shmem_shared_read(struct shmem_shared *shm, struct sample *smps[], unsigned cnt);
 
+/** Write samples to VILLASNode.
+ * @param[shm] The shared memory structure.
+ * @param[smps] The samples to be written. Must be allocated from shm->pool.
+ * @param[cnt] Number of samples to write.
+ */
 int shmem_shared_write(struct shmem_shared *shm, struct sample *smps[], unsigned cnt);
 
+/** Returns the total size of the shared memory region with the given size of
+ * the input/output queues (in elements) and the given number of data elements
+ * per struct sample. */
 size_t shmem_total_size(int insize, int outsize, int sample_size);
diff --git a/src/test-shmem.c b/src/test-shmem.c
index 8b8a0c496..3db0b1908 100644
--- a/src/test-shmem.c
+++ b/src/test-shmem.c
@@ -25,7 +25,8 @@ struct shmem_shared *shared;
 void usage()
 {
 	printf("Usage: villas-test-shmem SHM_NAME VECTORIZE\n");
-	printf("  SHMNAME name of the shared memory object\n");
+	printf("  SHMNAME   name of the shared memory object\n");
+	printf("  VECTORIZE maximum number of samples to read/write at a time\n");
 }
 
 void quit(int sig)