Bluetooth HID Keyboard

Summary

This prototype was request by Daniel Flood to explore the possibility of make a low cost skooge-like Human Interface Device (HID). Brendan Halliday completed the prototype. The BlueDuino Rev2 is an Arduino compatible microcontroller development board based on the ATmega32U4 IC with Bluetooth 4.0 Blueduino Documentation from Supplier

Required Files:

Required Hardware:

  • Blueduino Board
  • FTDI or CP2102 USB-Serial converter.
  • Breadboard
  • Buttons
  • Hookup wires (Male-Male, Male-Female, Female-Female)
  • MicroUSB cable.

Tools

Soldering Iron

Preparation

NOTE: You must upload new firmware to the module if you command it into upgrade mode. Otherwise the module will stay in upgrade mode and seem bricked.

  • Wire the USB to UART converter and BlueDuino like so
USB to UART converterBlueDuino Rev2
RX RXI (Serial1)
TX TXO (Serial1)
GND GND

Activity Summary

  • Plug in the BlueDuino to a PC. Take note of which COM port it shows up as in Device Manager.
  • Plug in the USB to UART converter to the same PC. Take note of which COM port it shows up as in Device Manager.
  • Open Coolterm, click on Options, then set Port to the COM port for the USB to UART converter.
  • Set Baudrate to 9600.
  • You will get “OK” when you type “AT” and pressing ENTER.
  • So type “AT+SBLUP”, you will get “OK+SBLUP”. This means the cc254x module is ready for upgrade. It won't accept any other AT command now.
  • Disconnect in Coolterm and then close it.
  • Open Arduino and upload an empty sketch to the BlueDuino. An empty sketch will practically be void setup(){} void loop() {}
  • Open SerialBootTool, it will ask you what device family to use, select BLE.
  • Click on Select File and select the keyboard-1.0.bin file. Click Open.
  • Click on Port Settings and select the USB to UART serial port and baud rate 115200.
  • Click OK
  • Click Load Image
  • Wait a while. You will see the words “Download completed successfully”
  • You're done!

Arduino Sample Code

#include "AB_BLE.h"

#define BAUD_RATE 57600

AB_BLE ble(&Serial1);

const int buttonPin = 8;     // the number of the pushbutton pin

// variables will change:
int buttonState1 = 0;         // variable for reading the pushbutton status

void setup() {
  Serial1.begin(BAUD_RATE);
  pinMode(buttonPin, INPUT_PULLUP);
}

void loop() {
 // read the state of the pushbutton value:
 buttonState1 = digitalRead(buttonPin);
 // check whether a  pushbutton is pressed.
 // if it is, the buttonState is HIGH:
 
 if (buttonState1 == LOW) {    
  ble.print("AT+KEY=");
  ble.println("Hello world");
 }
 delay(500);
}

Notes and additions

  • This kind of bluetooth keyboard has an inherent delay of approximately 100 milliseconds which m,eans it may not be directly usable for bluetooth gamepads but great for simple interactivity.
  • The example I've provided above is not properly debounced, which means that it can trigger the keys being sent a few times before you let go. This is why there is a delay(500); as a workaround.
  • The key presses are sent by the ble.print(“AT+KEY=”); and ble.println(“Hello world”); lines, change “Hello world” for any phrase or keyboard key you want to be pressed.
  • This firmware does not seem to support anything other than the alphanumeric keys.

1. Feedback:

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3. Feedback:

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Files

  • workshops/prototypes/bluetoothkeyboard/start.txt
  • Last modified: 2020/06/09 16:07
  • by Michelle Brown