com: added remarks.

avr/com.asm

@@ -172,6 +172,7 @@ COM_EnqueuePing:
     rcall RingBuffer_Alloc
   pop r17
   brcc COM_EnqueuePing_error
+  ; write header stuff
   mov r18, r16
   mov r20, r16                  ; r20: start of packet in ring buffer
   ldd r19, y+RINGBUFFER_OFFS_MAXSIZE
@@ -179,6 +180,7 @@ COM_EnqueuePing:
   rcall RingBuffer_Write       ; write length
   clr r16
   rcall RingBuffer_Write       ; write flags
+  ; write payload
   mov r16, r17
   rcall RingBuffer_Write       ; write dest addr
   ldi r16, COM_CMD_PING