127 lines
5.1 KiB
Plaintext
127 lines
5.1 KiB
Plaintext
/**
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\addtogroup rf230mac
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@{
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*/
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/**
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* \defgroup macdoc SICSLoWMAC Implementation
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* @{
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\section macintro 1. Introduction
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The phase1 MAC implemented to support the IPv6/6LoWPAN stack within the Contiki
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project is a light weight yet adequate beginning. This phase supports point to
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point data connectivity between a router device and an end device. The router is
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the RZ USB stick from the ATAVRRZRAVEN kit. The end node is the AVR
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Raven from the ATAVRRZRAVEN kit. The picture below shows the complete ATAVRRZRAVEN kit.
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\image html raven.png
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The next phases will implement a commissioning concept including scan, and
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beacon generation. These kinds of primitives will allow dynamic network
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formation. Additionally, routing and low power/sleep will be implemented in
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following phases.
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\section macprereqs 2. Prerequisites
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See the \ref tutorialraven for required systems setup configuration.
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\section macoverview 3. MAC Overview
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This MAC follows the recommendations of RFC4944 with respect to data frames and
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acknowledgements (i.e. all data frames are acknowledged). At the time of this
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writing (phase 1) beacons (frames) and association events are not implemented.
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Additionally, data frames always carry both source and destination addresses.
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PANID compression (intra-pan) is not used so both source and destination PANID's
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are present in the frame.
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The SICSLoWMAC supports the IEEE 802.15.4 Data Request primitive and the Data
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Request Indication primitive. The data request primitive constructs a <b>proper</b>
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802.15.4 frame for transmission over the air while the data indication parses a
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received frame for processing in higher layers (6LoWPAN). The source code for
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the mac can be found in the sicslowmac.[c,h] files.
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To assemble a frame a MAC header is constructed with certain presumptions:
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-# Long source and destination addresses are used.
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-# A hard coded PANID is used.
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-# A hard coded channel is used.
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-# Acknowledgements are used.
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-# Up to 3 auto retry attempts are used.
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These and other variables are defined in mac.h.
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Given this data and the output of the 6LoWPAN function, the MAC can construct
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the data frame and the Frame Control Field for transmission.
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An IEEE 802.15.4 MAC data frame consists of the fields shown below:
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\image html dataframe.png
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The Frame Control Field (FCF) consist of the fields shown below:
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\image html fcf.jpg
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\note The MAC address of each node is expected to be stored in EEPROM and
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retrieved during the initialization process immediately after power on.
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\section macrelationship 4. 6LoWPAN, MAC and Radio Relationship
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The output function of the 6LoWPAN layer (sicslowpan.c) is the input function
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to the MAC (sicslowmac.c). The output function of the MAC is the input function
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of the radio (radio.c). When the radio receives a frame over the air it processes
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it in its TRX_END event function. If the frame passes address and CRC filtering
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it is queued in the MAC event queue. Subsequently, when the MAC task is processed,
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the received frame is parsed and handed off to the 6LoWPAN layer via its input
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function. These relationships are depicted below:
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\image html layers.png
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\section maccode 5. Source Code Location
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The source code for the MAC, Radio and support functions is located in the path:
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- \\cpu\\avr\\radio
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- \\rf230
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- \\mac
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- \\ieee-manager
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-# The \\rf230 folder contains the low level HAL drivers to access and control
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the radio as well as the low level frame formatting and parsing functions.
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-# The \\mac folder contains the MAC layer code, the generic MAC initialization
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functions and the defines mentioned in section 3.
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-# The \\ieee-manager folder contains the access functions for various PIB
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variables and radio functions such as channel setting.
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The source code for the Raven platforms is located in the path:
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- \\platform
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- \\avr-raven
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- \\avr-ravenlcd
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- \\avr-ravenusb
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-# The \\avr-raven folder contains the source code to initialize and start the
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raven board.
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-# The \\avr-ravenlcd folder contains the complete source code to initialize
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and start the ATmega3209P on raven board in a user interface capacity. See the
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Doxygen generated documentation for more information.
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-# The \\avr-ravenusb folder contains the source code to initialize and start
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the raven USB stick as a network interface on either Linux or Windows platforms.
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Note that appropriate drivers are located in the path:
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- \\cpu\\avr\\dev\\usb\\INF
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\section macavrstudio 6. AVR Studio Project Location
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There are two projects that utilize the Logo Certified IPv6 and 6LoWPAN layers
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contributed to the Contiki project by Cisco. These are ping-ipv6and webserver-ipv6
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applications. They are located in the following paths:
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- \\examples\\webserver-ipv6
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and
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- \\examples\\ping-ipv6
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The ping-ipv6 application will allow the USB stick to ping the Raven board while
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the webserver-ipv6 application will allow the raven board to serve a web page.
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When the ravenlcd-3290 application is programmed into the ATmega3290P on the
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Raven board, the Raven board can ping the USB stick and it can periodically update
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the temperature in the appropriate web page when served.
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*/
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/** @} */
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/** @} */ |