SERA Actuator/Communications Spec

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Contents

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

A quick whiteboard plus/minus diagram.
A quick whiteboard plus/minus diagram.
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
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