Published January 29, 2020 © CC BY

ESP32 Bluetooth LE HID Keyboard

With a keyboard, you can control anything, from your phone, iPad, laptop. This will give Arduino the power it needs to control any screen.

AdvancedFull instructions provided41,282

Things used in this project

Hardware components

Geekworm EASY KIT ESP32-C1

Any ESP32 dev board would do, please note that the Arduino WiFi and Arduino BLE NANO aren't yet supported by the library

Adafruit Large Arcade button white

Optional, any button or wire would do

Breadboard (generic)

Micro-USB to USB Cable (Generic)

Jumper wires (generic)

Story

It is quite tricky to get Arduino (and it's hardware connected to it) talking to a screen; like a phone, iPad or laptop. This code helps you to connect Arduino to all kinds of experiences. Like playing Spotify, making a photobooth (where a sensor or button triggers making the picture), playing games or prototyping hardware connected apps.

Here you see a button being pressed, controlling the chrome waiting game of a dinosaur that jumps when the button is pressed.

It is a bit like Makey Makey, that made it possible to connect to laptops (or devices that allow USB); this library can help you to create wireless connections from the ESP32 to anything that supports Bluetooth low energy (BLE).

Bluetooth keyboards are a great way to connect Arduino to a phone to make these prototypes. We used the Bluetooth keyboard-chip from Adafruit (The bluefruit EZ-key) a lot for making remote controls talk to iPads or other digital devices within my internship at LEGO. Because we wanted full control over what the buttons would send to the iPad, we put an Arduino Nano in between that could send a character on press and one on release.

Experience prototypes for the LEGO train, where an Arduino Nano was controlling the Bluefruit EZ-key based on the inputs that it got from the buttons. Picture by: Oliver Wallington, Product technology

Now that the ESP32 chip arrived it is easier to create BLE experiences than ever; making the ESP32 chip talk like a keyboard is a great way to have everything at one chip, which reduces space, cost and increases possibilities.

People like T-vK and chegewara have made it easier than ever to make the ESP talk like a Bluetooth keyboard by creating a library for the Arduino software that makes it possible with just a few lines to send keystrokes to any device (that supports BLE)

Steps

Install Arduino (probably already done ;) )
Install the ESP32 boards (using the board manager), see instructions here
Install the ESP32-keyboard library (see the installation tab on the GitHub) it is not yet in the library manager.
Connect the button (could be any pushbutton, or just a wire connecting the 3.3V to the pin 13; don't connect 5V to it; it might damage your board!)
Download the example from this project hub
And start playing

Extending

Of course, the possibilities aren't limited to a single key, it is just a fast and simple example that can show the power, you could f.e. also connect a potentiometer where the value defines what character is being sent out.

Here you see a rotational interface that changes the amount of information on a mobile phone; displaying a future social network.

In one of my experiences for the Fluid Assemblage course, a device is being used to set the privacy level of a social network; in this case, it is challenging the fact that our networks and social network pages are always on; what if we can turn them off; or make them fade a certain moment in time.

The app on the phone is prototyped in Adobe XD, which allows for smooth transitions and keyboard control of the screens, so the potentiometer is sending 0, 1, 2, 3, 4 depending on where the potentiometer is, XD changes the screen when a number is pressed on the keyboard.

Game controller

I've got some requests on how this could be used as a controller for flight simulators, there is some good news, LemmingDev developed a specific library based on the ESP32-BLE-Keyboard library for game controllers called ESP32-BLE-Gamepad, which allows you to connect joysticks and other HID peripherals to your games. You could use GamePadViewer to test if the controller is working.

Limitations

With this tutorial, you can send information from the Arduino to the phone.

This is an example of connecting the ESP32 to P5 using UART/Serial bluetooth low energy

If you want to send data back and forth between the phone and the Arduino you could use the BLE UART protocol, I've made a tutorial on how to use this nowadays it becomes easier since even browsers have the ability to connect to BLE devices.

If it doesn't need to be wireless, or connecting to a phone you could use the web serial, which I described in this tutorial. Then you could use any Arduino compatible board since you don't need the Bluetooth functionality of the ESP.

Also, note that this code only works for ESP32 chips for now...

Code

/*
@Title BLE keyboard, arcade button to phone
@Author Geert Roumen
@Institute Umeå Institute of Design
@Date 29-01-2020
 
@Hardware
 
Any ESP32 dev board would do, but I used the:
Geekworm EASY KIT ESP32-C1
https://geekworm.com/products/official-geekworm-esp32-development-board

Arcade button
Adafruit Large Arcade button white
https://www.adafruit.com/product/1192

D13       Button pin
3.3V      Connected to the other leg of the button
 
In this example sketch one single button will send a spacebar when being pressed.
*/
#include <BleKeyboard.h>
//Se the name of the bluetooth keyboard (that shows up in the bluetooth menu of your device)
BleKeyboard bleKeyboard("Arcade Phone");

const int buttonPin = 13;
//Set the old button state to be LOW/false; which means not pressed
boolean oldPinState = LOW;

void setup() {
  //Start the Serial communication (with the computer at 115200 bits per second)
  Serial.begin(115200);
  //Send this message to the computer
  Serial.println("Starting BLE work!");
  //Begin the BLE keyboard/start advertising the keyboard (so phones can find it)
  bleKeyboard.begin();
  //Make the button pin an INPUT_PULLDOWN pin, which means that it is normally LOW, untill it is pressed/ connected to the 3.3V
  pinMode(buttonPin, INPUT_PULLDOWN);
}

void loop() {

  if (bleKeyboard.isConnected()) {
    //if the keyboard is connected to a device
    if (digitalRead(buttonPin) == HIGH) {
      //If the button pin is pressed (since it is pulled down, it is pressed when it is high
      if (oldPinState == LOW) {
        //if the old Pin state was LOW and the button pin is HIGH than...
        //send the spacebar
        bleKeyboard.print(" ");
        //or you can comment this one out, and it will send the newline character
        //bleKeyboard.write(KEY_RETURN);
      }
      oldPinState = HIGH;
    } else {
      oldPinState = LOW;
    }
  }
  delay(10);
}

/*
@Title BLE keyboard
@Author Geert Roumen
@Institute Umeå Institute of Design
@Date 20-03-2020
 
@Hardware
 
Any ESP32 dev board would do, but I used the:
Geekworm EASY KIT ESP32-C1
https://geekworm.com/products/official-geekworm-esp32-development-board

Any buttons

D18-D23   Button pins  
GND       Connected to the other leg of the button
*/

#include <BleKeyboard.h>
//Set the name of the bluetooth keyboard (that shows up in the bluetooth menu of your device)
BleKeyboard bleKeyboard("Arcade Phone");
byte buttonPins[] =    {23,  22,   21,   19,   18};
char buttonChars[] =  {'a', 'b',  'c',  'd',  'e'};
boolean buttonStates[] = {false, false, false, false, false};
//Set the old button state to be LOW/false; which means not pressed
boolean oldPinState = LOW;

void setup() {
  
  //Start the Serial communication (with the computer at 115200 bits per second)
  Serial.begin(115200);
  //Send this message to the computer
  Serial.println("Starting BLE work!");
  //Begin the BLE keyboard/start advertising the keyboard (so phones can find it)
  bleKeyboard.begin();
  //Make the button pin an INPUT_PULLUP pin, which means that it is normally HIGH, untill it is pressed/ connected to the GND/0V
  for(int i=0;i<sizeof(buttonPins);i++){
    pinMode(buttonPins[i], INPUT_PULLUP);
    
    }
}

void loop() {

  if (bleKeyboard.isConnected()) {
    for(int i=0;i<sizeof(buttonPins);i++){
      boolean state = digitalRead(buttonPins[i]);
      if (state != buttonStates[i]){
        if (state == LOW){
          bleKeyboard.press(buttonChars[i]);
          }else{
            bleKeyboard.release(buttonChars[i]);
            }
            buttonStates[i] = state;
        }
    }
  }
}

Credits

Geert Roumen

6 projects • 10 followers

I’m a maker and interaction designer, bridging the digital and physical world. and make prototypes and do research in a playful way.

ESP32 Bluetooth LE HID Keyboard

Things used in this project

Hardware components

Story

Steps

Extending

Game controller

Limitations

Schematics

Most simple setup, with breadboard button

Arcade setup

Arcade button connections

Code

ESP32 to ble keyboard to phone

ESP32 Game controller

Credits

Geert Roumen

Comments

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ESP32 Bluetooth LE HID Keyboard

ESP32 Bluetooth LE HID Keyboard

Things used in this project

Hardware components

Story

Steps

Extending

Game controller

Limitations

Schematics

Most simple setup, with breadboard button

Arcade setup

Arcade button connections

Code

ESP32 to ble keyboard to phone

ESP32 Game controller

Credits

Geert Roumen

Comments

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