SERA Actuator/Communications Spec

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Contents 1 What We Want 2 Protocols we are NOT Using 3 Protocols we should consider 4 Relevant Links

What We Want

• 640kbps synchronous
• daisy-chaining

Protocols we are NOT Using

• I2C
  • Intended for on-board comm.
• SPI
  • Intended for on-board comm.
  • Need 1 wire/device.
• RS-232
  • Max bandwidth is 115kbps, which is 1/6 of what we need.
• Microwire
  • Intended for on-board comm.
• Dallas's 1-Wire Bus
  • 16kbps max.
• RS-422
  • Multicast from master->slave
  • Requires 1 link/device for slave->master communication.
  • 10 UL (Unit Load) limit, i.e. 10 device limit
• LIN
  • 20kbps max.
• Zigbee
  • 250kbps max.

Protocols we should consider

Protocol	Bandwidth	Duplex	Max Length	Wires	Max Devices	Daisy Chainable?	Power	Notes
RS-485	35Mbps	Half	10m	9	32UL Worth	Y	No	Needs Termination and Magic
100-Base-T	100Mbps	Full	100m	4 or 8	IP Space Limited	Sorta	PoE	Galvanically Isolated. needs Hubs
USB	12Mbps	Half	5m	4	127	Sorta	5V	Needs Hubs at all Nodes
IEEE1394A	400Mbps	Full?	4.5m	6	63	Y	45W @ 30V
CAN	1Mbps	Half	40m	2	HLP Dependant	Y	No	Needs Termination and Magic

Relevant Links

• [1]
• Wikipedia