Narada

This project is just for fun. It lets you show others that you are busy with an audio or video call by lifting a flag. Yes, a real flag. It works with Skype, Zoom, Teams, etc.

Limitation

This project is designed for Linux users and has been tested on Ubuntu only.

How to use

Install

1. Build Arduino device
2. Upload device.ino to device (make sure to set correct pins for led and servo)
3. Plug in your device into USB port
4. Clone this repository

git clone https://github.com/igorzel/narada.git

5. Check Arduino's Vendor and Product using lsusb, for example Vendor is 1a86 and Product is 7523
6. Set Vendor and Product in 95-narada.rules file
7. Locate Arduino device serial port in this directory /dev/serial/by-id/, for example it can be /dev/serial/by-id/usb-1a86_USB2.0-Serial-if00-port0
8. Set serial port in narada.sh and narada.service files
9. Disconnect device from USB
10. Run

sudo ./install.sh

11. Plug in your device into USB port again
12. Make an audio or video call

Uninstall

1. Disconnect device from USB
2. Run

sudo ./uninstall.sh

How it works

The project consists of two components:

• A Bash script that runs on Linux and detects whether the microphone is in use or not and sends commands to Arduino device using serial port
• An Arduino device that controls a servo motor to raise or lower a flag accordingly

Linux part

Bash script

narada.sh is a script that detects whether the microphone is in use or not.

High level logic:

1. Setup serial device using stty
2. Every 10 seconds check if any of microphone device is in RUNNING state using cat and grep.

All the magic is here:

cat /proc/asound/card?/pcm*c/sub0/status 2>/dev/null | grep -q "state: RUNNING"

3. If any of the microphones is in RUNNING state then send command ON to serial port, if not - send OFF

systemd service

narada.service systemd unit runs the bash script as a service. Service starts automatically when device is plugged in (see udev). After device is disconected service stops.

udev

95-narada.rules is an udev rule to set permissions for Arduino serial device and start systemd unit service if device is plugged in.

Arduino device

drawn in https://www.circuito.io/

High level logic in device.ino:

1. Setup serial port
2. Set Led pin mode to OUTPUT
3. Listen to serial event
4. When command received attach servo
5. If command is ON:
   • Move servo to lift a flag with step 1 and delay
   • Set Led pin to HIGH to turn it on
6. If command is OFF:
   • Set Led pin to LOW to turn it off
   • Move servo to lower a flag with step 1 and delay
7. Detach servo