Network I/O Protocols

• TCP/IP (internet)
• RF / Wifi
• Packet Radio
• EDI
• Telephone
• Ethernet
• CAN

• Virtual Private Networking

The OSI Network Reference Layers, IO@, Cables@

The difference between a "serial bus" and a "serial interface" and a "network protocol" is blurring -- see busses (Modbus, X10, USB, MIDI, etc.), serial IO (RS485, SPI, etc.). See also:

• spamfrank23 at spamsofthome.net refers to

  http://yaspnet.sourceforge.net/ YASP: A simple and open protocol for building networks with small microcontrollers.
  
  Protocol features:
  
  * Adresses length: 1 to n bytes
  * Medium access: CDMA/CS/NDA (Carrier Sense Multiple Access / Collision Detection / Non-Destructive Arbitration)
  * Addressing modes: unicast, broadcast and multicast
  * Smallest frame: 6 bytes
  * Error detection: CRC16
  * Physical layer: 1-wire "open collector" or 2-wire diferential (CAN transceiver)
  * Current PIC implementation: about 480 words of code and 25 bytes of RAM (interrupt driven)
  * License: LGPL
  

• The Network Administrators Guide by Olaf Kirch
• http://www.csdmag.com/newframe.htm
• http://cio-europe.cisco.com/univercd/data/doc/cintrnet/75818.htm Cisco, Internetworking Technology Overview
• http://www.practicallynetworked.com/ "Practically Networked has provided practical, easy-to-understand help for small network builders since early 1998"
• http://www.smartcomputing.com/editorial/article.asp?article=articles%2Farchive%2Fg0806%2F15g06%2F15g06%2Easp Selecting A Home Network Kit - Choose The Right Tools For Putting PCs In Touch
• http://members.tripod.com/~mdileo/ Tiny Embedded Network
• http://www.elmelectronics.com/
• LON - http://www.lonmark.org  
  peer-to-peer serial protocol. It supports heirarchical addressing (scalable up to 32K nodes in a logical network), multi-drop, multiple media - twisted pair, RF, Fiber, powerline (or a mix of media in a logical network). Since it is peer-to-peer, every node can act as a master or you can implement a mult-master architecture. The protocol is done and implemented in silicon available from multiple sources. Echelon wants to charge $5 per node (!) for use and restricts doc's/changes spec to enforce this.
• CEBUS http://www.cebus.com
  The powerline version of the physical layer is starting to exceed 10Mbit/s, blowing away the 120 bit/s of X10, and there are physical layer specs for RS485, RF, IR, etc. The problem of custom chips is still there, but the price is reasonable, and there are at least a couple sources. Also, there is huge buy in as this is supposed to be the new home automation standard. Lucent, Cutler Hammer, and Microsoft, to name a few.
  CEBUS packets allow the addressing of 0xFFFF homes with 0xFFFF nodes, sending 256 bytes data per packet. Data is context sensitive. ie. A TV will have volume up/down power on/off channel up/down pip on/off etc. A light switch will have power on/off dim up/down. Thus your packetization is as simple as your device and doesn't require a big micro implementing 17 software layers to turn on a light bulb!
  • For an example product, see http://www.intelogis.com They make a powerline peer to peer networking solution for sharing data between 2 computers and sharing a printer. 10Mbit over power line, $99 for the package. And they now have an open source policy.
• SNAP - http://www.hth.com/snap/ free and open , easy to learn and light weighted network protocol
• HDLC - Very mature.

  Frame structure

  FLAG            ADDRESS Payload         CRC             FLAG
  (8bits)         (0-16Bits)  (8 * N Bits)        (16 Bits)       (8Bits)
  

  • The flag is a fixed byte (often 0b01111110 or 0x7E)
  • The flag must be escaped if it appears in the data stream.
    

• Ken Websters PIC16C74 serial port multiplexer. This includes a packet system with addressing, control, checksums, etc... Actually almost a network (OSI 3) system.

See:

• /techref/microchip/rs485-fav.htm RS485 Networking for intelligent house by Frank A. Vorstenbosch+

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