Skin Networking

Communication Protocols

I2C?

• Inter-Integrated Circuit
• Uses only 2 lines, Serial Data (SDA) and Serial Clock (SCL).
• Designed for short range, inter-chip communication
• Both lines are open drain, allowing many devices to attach to each line with only a single pull-up resistor
• Typical voltage levels of +5 V or +3.3 V are used (Logic standard levels).
• Maximum of 112 nodes on a I2C? bus w/ 7 bit address space, but 10 bit addressing can be used.
• 100 and 400 kbits/s standard bus speeds, but speeds as high as 3.4 Mbits/s are allowed.
• Maximum total bus capacitance of 400 pF limits number of nodes on bus and wire length.
• In general, a I2C? is a high speed serial bus structure for short range inter-chip networks.
• See Wikipedia article here, I2C Wikipedia -- JohnUlmen - 05 Aug 2008

CAN

• Controller Area Network
• Developed for automotive applications, CAN has spread in use.
• Designed for robust communication in small networks.
• 1 Mbit/s achievable with lines shorter than 40 m.
• Arbitration achieved by dominant and recessive addresses: more dominant addresses (those with logic level low high significance bits) dominate communication lines, and recessive address devices take note and stop transmitting.
• Licensed by Bosch, fees may apply for use.
• See Wikipedia article here, CAN-bus Wikipedia -- JohnUlmen - 05 Aug 2008

I2C? Development

• Demo Board - http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en023561&part=DM300018
• Chip - http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1335&dDocName=en010345
• Reference Manual http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2574
• PIC Lessons http://www.amqrp.org/elmer160/index.html -- -- DanAukes - 30 Jul 2008