Example of HID Keyboard BLE with ESP32

ESP32_HID.ino

#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEServer.h>
#include "BLE2902.h"
#include "BLEHIDDevice.h"
#include "HIDTypes.h"
#include "HIDKeyboardTypes.h"
#include <driver/adc.h>

BLEHIDDevice* hid;
BLECharacteristic* input;
BLECharacteristic* output;

uint8_t buttons = 0;
uint8_t button1 = 0;
uint8_t button2 = 0;
uint8_t button3 = 0;
bool connected = false;

class MyCallbacks : public BLEServerCallbacks {
  void onConnect(BLEServer* pServer){
    connected = true;
    BLE2902* desc = (BLE2902*)input->getDescriptorByUUID(BLEUUID((uint16_t)0x2902));
    desc->setNotifications(true);
  }

  void onDisconnect(BLEServer* pServer){
    connected = false;
    BLE2902* desc = (BLE2902*)input->getDescriptorByUUID(BLEUUID((uint16_t)0x2902));
    desc->setNotifications(false);
  }
};

/*
 * This callback is connect with output report. In keyboard output report report special keys changes, like CAPSLOCK, NUMLOCK
 * We can add digital pins with LED to show status
 * bit 0 - NUM LOCK
 * bit 1 - CAPS LOCK
 * bit 2 - SCROLL LOCK
 */
 class MyOutputCallbacks : public BLECharacteristicCallbacks {
 void onWrite(BLECharacteristic* me){
    uint8_t* value = (uint8_t*)(me->getValue().c_str());
    ESP_LOGI(LOG_TAG, "special keys: %d", *value);
  }
};

void taskServer(void*){


    BLEDevice::init("Backpack-MeowMeow");
    BLEServer *pServer = BLEDevice::createServer();
    pServer->setCallbacks(new MyCallbacks());

    hid = new BLEHIDDevice(pServer);
    input = hid->inputReport(1); // <-- input REPORTID from report map
    output = hid->outputReport(1); // <-- output REPORTID from report map

    output->setCallbacks(new MyOutputCallbacks());

    std::string name = "ElectronicCats";
    hid->manufacturer()->setValue(name);

    hid->pnp(0x02, 0xe502, 0xa111, 0x0210);
    hid->hidInfo(0x00,0x02);

  BLESecurity *pSecurity = new BLESecurity();
//  pSecurity->setKeySize();
  pSecurity->setAuthenticationMode(ESP_LE_AUTH_BOND);

    const uint8_t report[] = {
      USAGE_PAGE(1),      0x01,       // Generic Desktop Ctrls
      USAGE(1),           0x06,       // Keyboard
      COLLECTION(1),      0x01,       // Application
      REPORT_ID(1),       0x01,        //   Report ID (1)
      USAGE_PAGE(1),      0x07,       //   Kbrd/Keypad
      USAGE_MINIMUM(1),   0xE0,
      USAGE_MAXIMUM(1),   0xE7,
      LOGICAL_MINIMUM(1), 0x00,
      LOGICAL_MAXIMUM(1), 0x01,
      REPORT_SIZE(1),     0x01,       //   1 byte (Modifier)
      REPORT_COUNT(1),    0x08,
      HIDINPUT(1),           0x02,       //   Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position
      REPORT_COUNT(1),    0x01,       //   1 byte (Reserved)
      REPORT_SIZE(1),     0x08,
      HIDINPUT(1),           0x01,       //   Const,Array,Abs,No Wrap,Linear,Preferred State,No Null Position
      REPORT_COUNT(1),    0x06,       //   6 bytes (Keys)
      REPORT_SIZE(1),     0x08,
      LOGICAL_MINIMUM(1), 0x00,
      LOGICAL_MAXIMUM(1), 0x65,       //   101 keys
      USAGE_MINIMUM(1),   0x00,
      USAGE_MAXIMUM(1),   0x65,
      HIDINPUT(1),           0x00,       //   Data,Array,Abs,No Wrap,Linear,Preferred State,No Null Position
      REPORT_COUNT(1),    0x05,       //   5 bits (Num lock, Caps lock, Scroll lock, Compose, Kana)
      REPORT_SIZE(1),     0x01,
      USAGE_PAGE(1),      0x08,       //   LEDs
      USAGE_MINIMUM(1),   0x01,       //   Num Lock
      USAGE_MAXIMUM(1),   0x05,       //   Kana
      HIDOUTPUT(1),          0x02,       //   Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position,Non-volatile
      REPORT_COUNT(1),    0x01,       //   3 bits (Padding)
      REPORT_SIZE(1),     0x03,
      HIDOUTPUT(1),          0x01,       //   Const,Array,Abs,No Wrap,Linear,Preferred State,No Null Position,Non-volatile
      END_COLLECTION(0)
    };

    hid->reportMap((uint8_t*)report, sizeof(report));
    hid->startServices();

    BLEAdvertising *pAdvertising = pServer->getAdvertising();
    pAdvertising->setAppearance(HID_KEYBOARD);
    pAdvertising->addServiceUUID(hid->hidService()->getUUID());
    pAdvertising->start();
    hid->setBatteryLevel(7);

    ESP_LOGD(LOG_TAG, "Advertising started!");
    delay(portMAX_DELAY);
  
};

void setup() {
  Serial.begin(115200);
  Serial.println("Starting BLE work!");

  pinMode(12, INPUT_PULLDOWN);
  attachInterrupt(digitalPinToInterrupt(12), clickNumLock, CHANGE);   // Num Lock
  pinMode(14, INPUT_PULLDOWN);
  attachInterrupt(digitalPinToInterrupt(13), clickCapsLock, CHANGE);   // Caps Lock
  pinMode(32, INPUT_PULLDOWN);
  attachInterrupt(digitalPinToInterrupt(32), clickScrollLock, CHANGE);   // Scroll Lock

  xTaskCreate(taskServer, "server", 20000, NULL, 5, NULL);
}

void loop() {
  
  if(connected){

    vTaskDelay(5000);
    const char* hello = "Hello world from esp32 hid keyboard!!!\n";

    while(*hello){
      KEYMAP map = keymap[(uint8_t)*hello];
      Serial.println(buttons);
      uint8_t msg[] = {map.modifier || buttons, 0x0, map.usage, 0x0,0x0,0x0,0x0,0x0};
      input->setValue(msg,sizeof(msg));
      input->notify();
      hello++;
      uint8_t msg1[] = {0x0, 0x0, 0x0, 0x0,0x0,0x0,0x0,0x0};

      input->setValue(msg1,sizeof(msg1));
      input->notify();
      delay(10);
    }
  }
  delay(50);
}

IRAM_ATTR void clickNumLock(){
  button1 = buttons&&0x01;
  button1 != button1;
  buttons = button1<<0;
}
IRAM_ATTR void clickCapsLock(){
  button2 = buttons&&0x02;
  button2 != button2;  
  buttons = button2<<1;
}
IRAM_ATTR void clickScrollLock(){
  button3 = buttons&&0x04;
  button3 != button3;  
  buttons = button3<<2;
}