added more descriptive comments about the header

diff --git a/tos/chips/cc2420/CC2420.h b/tos/chips/cc2420/CC2420.h
index 1d607b921763c87608ea2e6e4266c17359c25901..798107f0ebcb0367ee9e7822cfc8d1b5d0ca095c 100644 (file)
--- a/tos/chips/cc2420/CC2420.h
+++ b/tos/chips/cc2420/CC2420.h
@@ -43,8 +43,43 @@ typedef uint8_t cc2420_status_t;
 #endif
 
 /**
- * CC2420 header.  An I-frame (interoperability frame) header has an 
- * extra network byte specified by 6LowPAN
+ * CC2420 header definition.
+ * 
+ * An I-frame (interoperability frame) header has an extra network 
+ * byte specified by 6LowPAN
+ * 
+ * Length = length of the header + payload of the packet, minus the size
+ *   of the length byte itself (1).  This is what allows for variable 
+ *   length packets.
+ * 
+ * FCF = Frame Control Field, defined in the 802.15.4 specs and the
+ *   CC2420 datasheet.
+ *
+ * DSN = Data Sequence Number, a number incremented for each packet sent
+ *   by a particular node.  This is used in acknowledging that packet, 
+ *   and also filtering out duplicate packets.
+ *
+ * DestPan = The destination PAN (personal area network) ID, so your 
+ *   network can sit side by side with another TinyOS network and not
+ *   interfere.
+ * 
+ * Dest = The destination address of this packet. 0xFFFF is the broadcast
+ *   address.
+ *
+ * Src = The local node ID that generated the message.
+ * 
+ * Network = The TinyOS network ID, for interoperability with other types
+ *   of 802.15.4 networks. 
+ * 
+ * Type = TinyOS AM type.  When you create a new AMSenderC(AM_MYMSG), 
+ *   the AM_MYMSG definition is the type of packet.
+ * 
+ * TOSH_DATA_LENGTH defaults to 28, it represents the maximum size of 
+ * the payload portion of the packet, and is specified in the 
+ * tos/types/message.h file.
+ *
+ * All of these fields will be filled in automatically by the radio stack 
+ * when you attempt to send a message.
  */
 typedef nx_struct cc2420_header_t {
   nxle_uint8_t length;