moved support for shimmer* here (except for hpl) with re-worked

[tinyos-2.x.git] / doc / txt / tep113.txt

diff --git a/doc/txt/tep113.txt b/doc/txt/tep113.txt
index bcf94e193409478ece2c43fe8ca14248c785459c..c631df7c2cacb5db2ef774e4c64924a733575b5a 100644 (file)
--- a/doc/txt/tep113.txt
+++ b/doc/txt/tep113.txt
@@ -5,15 +5,10 @@ Serial Communication
 :TEP: 113
 :Group: Core Working Group 
 :Type: Documentary
 :TEP: 113
 :Group: Core Working Group 
 :Type: Documentary

-:Status: Draft
+:Status: Final

 :TinyOS-Version: 2.x
 :Author: Ben Greenstein and Philip Levis
 
 :TinyOS-Version: 2.x
 :Author: Ben Greenstein and Philip Levis
 

-:Draft-Created: 11-Jul-2005
-:Draft-Version: $Revision$
-:Draft-Modified: $Date$
-:Draft-Discuss: TinyOS Developer List <tinyos-devel at mail.millennium.berkeley.edu>
-

 .. Note::
 
    This memo documents a part of TinyOS for the TinyOS Community, and
 .. Note::
 
    This memo documents a part of TinyOS for the TinyOS Community, and


@@ -278,6 +273,25 @@ stored in a queue separate from the data buffer, so a data packet to
 be transmitted may begin spooling into SerialP while SerialP is
 actively sending an acknowledgement.
 
 be transmitted may begin spooling into SerialP while SerialP is
 actively sending an acknowledgement.
 

+Only the PC-to-mote communication path supports acknowledgements.
+SerialP does not request acknowledgements from the PC for two reasons.
+First, acks are not perfect reliable: they are used on the
+PC-to-mote path to raise reliability to a usable level. In the case of
+the PC-to-mote path, the UART receive buffer is typically a single
+byte, so a high interrupt load can easily lose (and sometimes does) a
+byte. This is in contrast to the PC receive buffer, which is much
+larger and does not have to deal with overflow. Second, adding support
+for acks would increase the code size and complexity of the serial
+stack. As code space is often at a premium, this would add little
+needed functionality at significant cost. Of course, any application
+that requires perfect reliability may layer its own scheme on top of
+the serial protocol.
+
+The acknowledgement protocol is stop-and-wait to minimize buffering on
+the mote side. This is considered more important on memory constrained
+devices than increased throughput in the PC-to-mote direction, which
+most applications only use for occasional control transmissions.
+

 
 3.4 Dispatcher: SerialDispatcherC
 --------------------------------------------------------------------
 
 3.4 Dispatcher: SerialDispatcherC
 --------------------------------------------------------------------


@@ -467,6 +481,8 @@ no snooping capabilities.
 
 .. [TEP116] TEP 116: Packet Protocols. tinyos-2.x/doc/txt/tep116.txt
  
 
 .. [TEP116] TEP 116: Packet Protocols. tinyos-2.x/doc/txt/tep116.txt
  

+.. [TEP117] TEP 117: Low-Level I/O. tinyos-2.x/doc/txt/tep117.txt
+

 .. [HDLC] International Organization For Standardization, ISO Standard 3309-1979, "Data communication - High-level data link control procedures - Frame structure", 1979.
 
 .. [RFC1662] PPP in HDLC-like Framing, Internet Engineering Task Force (IETF), 1994
 .. [HDLC] International Organization For Standardization, ISO Standard 3309-1979, "Data communication - High-level data link control procedures - Frame structure", 1979.
 
 .. [RFC1662] PPP in HDLC-like Framing, Internet Engineering Task Force (IETF), 1994