Using a momentary footswitch instead of a mechanical key - HIDKeyboard Project

Hi all, first time doing this..

I have successfully setup my Feather 32u4 Bluefruit LE to act as an HID Keyboard via this tutorial.

Instead of keyboard keys, I want to use two of these momentary normally open foot switches. I have everything wired up, one side of the footswitch going to GRD, one side going to GPIO pin 12, which should type the letter A.

My code is reflected correctly to display a keypress. My device is paired, but nothing happens. I am sure these is some obvious reason, maybe these footswitches won't work the same as a keyboard key, but I would like to know why, and know if it is possible to use them.

Here is my code:

 This is an example for our nRF51822 based Bluefruit LE modules

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  This example shows how to send HID (keyboard/mouse/etc) data via BLE
  Note that not all devices support BLE keyboard! BLE Keyboard != Bluetooth Keyboard

#include <Arduino.h>
#include <SPI.h>
#if not defined (_VARIANT_ARDUINO_DUE_X_) && not defined(ARDUINO_ARCH_SAMD)
  #include <SoftwareSerial.h>

#include "Adafruit_BLE.h"
#include "Adafruit_BluefruitLE_SPI.h"
#include "Adafruit_BluefruitLE_UART.h"

#include "BluefruitConfig.h"
#include "keycode.h"


    FACTORYRESET_ENABLE       Perform a factory reset when running this sketch
                              Enabling this will put your Bluefruit LE module
                              in a 'known good' state and clear any config
                              data set in previous sketches or projects, so
                              running this at least once is a good idea.
                              When deploying your project, however, you will
                              want to disable factory reset by setting this
                              value to 0.  If you are making changes to your
                              Bluefruit LE device via AT commands, and those
                              changes aren't persisting across resets, this
                              is the reason why.  Factory reset will erase
                              the non-volatile memory where config data is
                              stored, setting it back to factory default
                              Some sketches that require you to bond to a
                              central device (HID mouse, keyboard, etc.)
                              won't work at all with this feature enabled
                              since the factory reset will clear all of the
                              bonding data stored on the chip, meaning the
                              central device won't be able to reconnect.
    MINIMUM_FIRMWARE_VERSION  Minimum firmware version to have some new features
    #define FACTORYRESET_ENABLE         0

// Create the bluefruit object, either software serial...uncomment these lines
SoftwareSerial bluefruitSS = SoftwareSerial(BLUEFRUIT_SWUART_TXD_PIN, BLUEFRUIT_SWUART_RXD_PIN);

Adafruit_BluefruitLE_UART ble(bluefruitSS, BLUEFRUIT_UART_MODE_PIN,

/* ...or hardware serial, which does not need the RTS/CTS pins. Uncomment this line */

/* ...hardware SPI, using SCK/MOSI/MISO hardware SPI pins and then user selected CS/IRQ/RST */

/* SPI, using SCK/MOSI/MISO user-defined SPI pins and then user selected CS/IRQ/RST */
//                             BLUEFRUIT_SPI_MOSI, BLUEFRUIT_SPI_CS,
//                             BLUEFRUIT_SPI_IRQ, BLUEFRUIT_SPI_RST);

// A small helper
void error(const __FlashStringHelper*err) {
  while (1);

typedef struct
  uint8_t modifier;   /**< Keyboard modifier keys  */
  uint8_t reserved;   /**< Reserved for OEM use, always set to 0. */
  uint8_t keycode[6]; /**< Key codes of the currently pressed keys. */
} hid_keyboard_report_t;

// Report that send to Central every scanning period
hid_keyboard_report_t keyReport = { 0, 0, { 0 } };

// Report sent previously. This is used to prevent sending the same report over time.
// Notes: HID Central intepretes no new report as no changes, which is the same as
// sending very same report multiple times. This will help to reduce traffic especially
// when most of the time there is no keys pressed.
// - Init to different with keyReport
hid_keyboard_report_t previousReport = { 0, 0, { 1 } };

// GPIO corresponding to HID keycode (not Ancii Character)
int inputPins[6]     = { 5        , 6        , 9        , 10       , 11       , 12        };
int inputKeycodes[6] = { HID_KEY_X, HID_KEY_Z, HID_KEY_D, HID_KEY_W, HID_KEY_S, HID_KEY_A };

    @brief  Sets up the HW an the BLE module (this function is called
            automatically on startup)
void setup(void)
  //while (!Serial);  // required for Flora & Micro

  Serial.println(F("Adafruit Bluefruit HID Keyboard Example"));

  /* Initialise the module */
  Serial.print(F("Initialising the Bluefruit LE module: "));

  if ( !ble.begin(VERBOSE_MODE) )
    error(F("Couldn't find Bluefruit, make sure it's in CoMmanD mode & check wiring?"));
  Serial.println( F("OK!") );

    /* Perform a factory reset to make sure everything is in a known state */
    Serial.println(F("Performing a factory reset: "));

  /* Disable command echo from Bluefruit */

  Serial.println("Requesting Bluefruit info:");
  /* Print Bluefruit information */;

  /* Change the device name to make it easier to find */
  Serial.println(F("Setting device name to 'Bluefruit Keyboard': "));
  if (! ble.sendCommandCheckOK(F( "AT+GAPDEVNAME=Bluefruit Keyboard" )) ) {
    error(F("Could not set device name?"));

  /* Enable HID Service if not enabled */
  int32_t hid_en = 0;
  ble.sendCommandWithIntReply( F("AT+BleHIDEn"), &hid_en);

  if ( !hid_en )
    Serial.println(F("Enable HID Service (including Keyboard): "));
    ble.sendCommandCheckOK(F( "AT+BleHIDEn=On" ));

    /* Add or remove service requires a reset */
    Serial.println(F("Performing a SW reset (service changes require a reset): "));
  Serial.println(F("Go to your phone's Bluetooth settings to pair your device"));
  Serial.println(F("then open an application that accepts keyboard input"));

  // Set up input Pins
  for(int i=0; i< 6; i++)
    pinMode(inputPins[i], INPUT_PULLUP);

    @brief  Constantly poll for new command or response data
void loop(void)
  /* scan GPIO, since each report can has up to 6 keys
   * we can just assign a slot in the report for each GPIO 
  if ( ble.isConnected() )
    for(int i=0; i<6; i++)
      // GPIO is active low     
      if ( digitalRead(inputPins[i]) == LOW )
        keyReport.keycode[i] = inputKeycodes[i];
        keyReport.keycode[i] = 0;

      // Only send if it is not the same as previous report
      if ( memcmp(&previousReport, &keyReport, 8) )
        // Send keyboard report
        ble.atcommand("AT+BLEKEYBOARDCODE", (uint8_t*) &keyReport, 8);

        // copy to previousReport
        memcpy(&previousReport, &keyReport, 8);

  // scaning period is 10 ms

Many thanks.

Do the correspond keys ('X', 'Z', 'D', 'W', 'S', 'A') get sent if you jumper any of the input pins (5, 6, 9, 10, 11, 12) to Ground? If that doesn't work, the problem is in your sketch. If it does work, the problem is in your footswitch wiring.

Thanks for the reply John, I am very new to this; would Tools > Serial Monitor be able to tell me what the Feather is doing so I could observe its function/behavior?

Once I know how to observe what the Feather is doing, I'll connect one of the input pins directly to the GRD as you suggest, and report back.

Only so far as you have Serial.print() statements to report what is happening.

@zachisback The installation and troubleshooting is NOT for problems with your project, only problems getting th Arduino system to work at the very basic level as downloading and running the simplest of codes.

I have moved you post to a more appropriate section of this forum.