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Serial server

In the serial server role, the board takes one USB serial adapter, and each of its ports becomes a TCP socket. Bytes from the line go to every connected client (up to 3 per port), and bytes from any client go out on the line.

Supported adapters​

  • FTDI FT232R and FT231X. The FT232H, FT2232H and FT4232H are not supported yet.
  • Silicon Labs CP210x, including the dual CP2105 and quad CP2108.
  • WCH CH340 and CH341.
  • Class-compliant adapters: WCH CH343, CH9102, CH342 and CH344 (dual and quad), and most others that show up as ttyACM on Linux.

Plug the adapter straight into the board: hubs are not supported. RS-485 adapters must switch direction on their own (most do).

Set up a port​

  1. Choose Serial server under Settings and Save & reboot.
  2. Plug in the adapter. The Serial ports panel shows it and a card for each port.
  3. On each port you want to use, tick Enabled: accept connections on this port and set:
Setting
Labela name for the port, for example Rooftop AHU
ProtocolRaw TCP passes bytes unchanged. RFC 2217 (client sets baud) is telnet with the COM port option: the client can set baud, data bits, parity, stop bits, DTR and RTS.
TCP port9000 for port 1, 9001 for port 2, and so on, by default
Baud, Data bits, Parity, Stop bitsthe line settings. There is no flow control.
Allowed clients (blank: anyone)IP addresses or networks, such as 192.168.1.0/24 10.0.0.5

Changes apply at once and are saved. Settings are kept by port number, so a replacement adapter picks them up.

With RFC 2217, settings a client makes last until the last client disconnects, then the saved ones come back.

Use the allow list

The admin password doesn't protect the serial sockets: anyone who can connect can write to the line. Fill in Allowed clients on anything that matters.

Connect​

python3 -m serial.tools.miniterm rfc2217://etherjax-XXXX.local:9000 9600
nc etherjax-XXXX.local 9000 | xxd       # raw

RFC 2217 works with pyserial's rfc2217://host:port, ser2net, and virtual COM port drivers. Z-Wave JS can open a raw socket as tcp://host:9000.

Each board advertises its enabled sockets over mDNS, and the matrix lists them.

Notes​

  • FTDI adapters get their latency timer set to 1 ms, so replies aren't held back for 16 ms.
  • There is no break signal, and no RS-485 direction control from RTS.
  • Protocols such as Modbus are for the client to speak over the socket.
  • A missing adapter, or a TCP port that can't be opened, shows as a problem on the page. The board doesn't reboot for either.