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Remote GPIO standard: Modbus over RS-485
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Is it an option to add Modbus over RS-485 to pilight?  It is a good match in terms of simplicity and unleashes remote GPIO actions over a simple twisted pair.

RS-485 in summary:
  • RS-485 can easily be connected to an RS-232 port
  • RS-485 uses symmetric signals over one twisted pair: long distances, high speeds
  • RS-485 implements a bus: 32 devices on a wire; more with amplification
  • RS-485 commonly runs Modbus as its protocol
Modbus in summary:
  • Modbus is a standard for addressing input/output devices
  • Modbus can run over RS-485 or TCP or TLS
  • Modbus assumes a single bus master that polls slaves
  • Modbus supports up to 247 slaves; and has a broadcast address
  • Modbus slaves typically have a configurable address
  • Modbus serial frames: SLAVE,COMMAND,DATA,CRC16
Typical devices range from low-cost to high-cost and include:
  • Relay blocks for output, switches for input
  • Sensors for temperature, humidity, ...
  • Thermostats with programmable setpoints
  • Energy meters: W, Wh, V, A, VAh, cos(φ)
There are cheap and simple ways to get on the bus for USB as well as for RS-232 (3V3, 5V or standard).

I think it makes a lot of sense in the pilight platform!
 
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Remote GPIO standard: Modbus over RS-485 - by vanrein - 07-13-2019, 10:07 AM

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