In this document, we will discuss various features LEDI. We will explain how to set it up and operate it. From here on, we will assume you have a completely assembled LEDI. We also assume you have an Android phone that can be used to communicate with LEDI.

Most features of LEDI can be controlled via Android App, LEDI Manager. It gives you the ability to interact with it without much fuss, and gives you intuitive control over electronics circuit you’ve assembled.

First download the App from Google Play:



Power up LEDI

Simply turn the power switch to the "on" position. Also, make sure the power supply voltage switch is set to "5v".

When it’s first powered up, LEDI will go into a clock mode. The clock starts at "00:00", since LEDI does not keep track of time when it’s powered off. Once powered on, however, it will constantly keep accurate time across various operating modes. Also in addition to HH:MM clock digits, you will see the binary indicator ticking every second.

Bluetooth Pairing

First, make sure Bluetooth radio is turned on in Settings.

Everytime LEDI’s power is reset, the bluetooth module will go into discoverable mode. Other bluetooth devices can easily scan and pair with LEDI. You will first need to pair LEDI with your Android device.

Let’s first "bond" with LEDI using an Android phone. Go to:

Settings -> Wireless Settings -> Bluetooth Settings

Hit scan for devices. Your device should show up and it will be called either

  • linvor
  • HC-05

Select the device and you will get a bluetooth pairing request. Use the passcode 1234 to establish the pairing.

LEDIManager Android App


We have written an Android app specifically designed to work with LEDI. This app is the main controller for LEDI which allows it to communicate with the "world".

LEDIManager sends various notifications from your Android phone to LEDI. It maintains stable connection to LEDI and allows user to interact with LEDI wirelessly.

The current list of LEDIManager features:

  1. Gmail, sms, call, alarm notifications supported
  2. Remotely set current time
  3. Send arbitrary message from your Android phone
  4. Virtual interface that allows you to "draw" on LEDI wirelessly

When you start the app

Your app will look like this:


First search for your LEDI and bond with it, by pressing the "Search" button on the App. If you haven’t already paired against it, it will prompt you for the passcode for pairing. (Remember 1234 to pair)


Once the search is done, select your LEDI. After your device is selected, it will bring you back to the main screen.


Establish connection

Press the large button on top that says "service off". It’s a toggle button that will turn green when the connection is properly established. If successful, your screen will look like this, and LEDI will greet you with a chime.


Send Commands

You can send simple messages to LEDI from a text box on the bottom of the screen, and then hitting "Send". This will scroll your text across LEDI.

Test Virtual LEDI

You’ll notice that there’s a button called vLEDI. This interface allows you to "draw" on LEDI from your Android. You can trace your finger across the virtual LEDI screen and see the same dots lit up on your LEDI!



Other Android Apps

There are slew of available Android Apps that just works with LEDI. Almost all of them are free. For example, I’ve tested:

LEDI uses Bluetooth module that understands SPP (Serial Port Profile). What this basically means is that it’s compatible with lots of bluetooth-enabled software out there.

Talk to it

Try downloading BlueTerm from the App store on your phone. I found it to be the simplest one to use when I was testing LEDI.

  1. Open the App
  2. Hit settings button on your phone
  3. Tap "Connect device"
  4. Tap "Scan for devices"
  5. Your LEDI will show up as one of the devices as "linvor" or "LEDI_XXX"
  6. It will say "Connected to <your_device>"
  7. Type something on the terminal
  8. Hit "enter" on your virtual keyboard

If everything went right, you will see the message you just typed scroll across LEDI.

Power Switches

There are 2 slide switches on the board. With the barrel jack faced down, the slide switch left of it is "on/off" switch. The slide switch to the right of the barrel jack is the "3v/5v" toggle switch. Slide the power switch up to turn the power on and supply regulated 5 volts to the circuit.

Tactile Buttons

There are 4 buttons on the board.

Button Name Description
Reset Located at the top, resets the microcontroller
Programmable Btn1 Currently puts LEDI into Conway’s game-of-life display
Programmable Btn2 Allows you to manually adjust time (short, long presses)
Bluetooth Reset Located near bluetooth module, resets the module

The behavior of both programmable buttons can be changed in the firmware.

Power Supply

The power circuit supplies either 5v or 3.3v of clean DC. There are access headers to either

  1. source power from other external voltage source (upto 9VDC)
  2. supply power to other circuits (5 or 3.3v)

We’ve taken the power schematics from Sparkfun‘s breadboard power supply.

You can source power from an external battery through the connector shown in the picture:

Or you can supply regulated power to other circuits through these pins on the PCB:

For example, I am powering the Arduino via the power output pins: