Edrys Serial Module

This module uses WebSerial to share a live serial terminal from a station with everyone in the station's room. It is useful for remote labs, for example to let students use an Arduino's serial monitor remotely.

The station connects to the device. Everything the device prints shows up in every participant's terminal, and anything a participant types is sent to the device.

WebSerial is not supported in all browsers. The station needs a browser that supports it: Chrome or Edge (89+), Opera (76+) or Firefox (151+), but not Safari. Students don't touch the serial port, so any browser works for them.

Usage

Add the module to your class with this URL:

https://edrys-labs.github.io/module-serial/

The module is only shown in stations (show-in: station), not in normal rooms.

1. Open the station.
2. Choose the baud rate in the header and click Connect.
3. Pick the device in the browser's port dialog.

Students join the station's room and can use the terminal right away.

The header shows the device status to everyone: not connected, connecting… or connected · 9600 baud. Students who type while no device is connected get a notice in the terminal; their input is not sent anywhere.

In the terminal:

• ctrl+shift+x copies the selection
• ctrl+shift+v pastes into the device

Errors are printed in the terminal, for example [could not connect: …] when the port is busy, or [serial error: …] after a wrong baud rate or a device reset.

Configuration

The module has one setting, under Station config in the module settings:

Field	Type	Default	Description
baud	number	9600	Default baud rate of the device

{
  "baud": 115200
}

Any baud rate works, including ones that are not in the dropdown (e.g. 74880). The configured value wins over the last rate chosen on the station. Without a configured value, the station remembers its own last choice.

For module developers

Other modules in the station's room can read from and write to the device through Edrys messages. The station listens in promiscuous mode, so messages from any module reach it.

Subject	Direction	Body
w	any peer → station	string, written to the device as is
r	station → everyone	string, output read from the device

// send a line to the device
Edrys.sendMessage('w', 'help\n')

// receive device output (promiscuous, since it comes from another module)
Edrys.onMessage(({ subject, body }) => {
  if (subject === 'r') console.log(body)
}, true)

The device status is kept in the room state under the key serial-status, as { state: 'on' | 'off' | 'wait', baud }:

const status = Edrys.getState('serial-status', 'Value')

Limitations

• Only one serial module per station room: two instances would share the same message subjects and status key.
• Disconnecting, or unplugging the device, reloads the module on the station; click Connect again to reconnect.

License

MIT © edrys-labs