Adafruit Feather 32u4 BLE UUID?

Hi there,

I have this nRF51822 BLE board and I’m trying to make an app with MIT App Inventor to control simple things like GPIO and read/write data via Bluetooth. Right now The only issue I have is actually sending/receiving data. I can connect to the BLE module but it’s not actually sending/receiving. This is because I can’t seem to figure out the proper UUID’s to use for the life of me, both in code or in the app. Here is sample Adafruit code that sets the service and char UUID’s:

 This is an example for our nRF51822 based Bluefruit LE modules

 Pick one up today in the adafruit shop!

 Adafruit invests time and resources providing this open source code,
 please support Adafruit and open-source hardware by purchasing
 products from Adafruit!

 MIT license, check LICENSE for more information
 All text above, and the splash screen below must be included in
 any redistribution

    Please note the long strings of data sent mean the *RTS* pin is
    required with UART to slow down data sent to the Bluefruit LE!  

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

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

#include "BluefruitConfig.h"

#include "IEEE11073float.h"

// 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);

Adafruit_BLEGatt gatt(ble);

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

/* The service information */

int32_t htsServiceId;
int32_t htsMeasureCharId;

    @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

  boolean success;

  Serial.println(F("Adafruit Bluefruit Health Thermometer 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: "));
  if (! ble.factoryReset() ){
       error(F("Couldn't factory reset"));

  /* Disable command echo from Bluefruit */

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

  // this line is particularly required for Flora, but is a good idea
  // anyways for the super long lines ahead!
  // ble.setInterCharWriteDelay(5); // 5 ms

  /* Add the Heart Rate Service definition */
  /* Service ID should be 1 */
  Serial.println(F("Adding the Health Thermometer Service definition (UUID = 0x1809): "));
  htsServiceId = gatt.addService(0x1809);
  if (htsServiceId == 0) {
    error(F("Could not add Thermometer service"));
  /* Add the Temperature Measurement characteristic which is composed of
   * 1 byte flags + 4 float */
  /* Chars ID for Measurement should be 1 */
  Serial.println(F("Adding the Temperature Measurement characteristic (UUID = 0x2A1C): "));
  htsMeasureCharId = gatt.addCharacteristic(0x2A1C, GATT_CHARS_PROPERTIES_INDICATE, 5, 5, BLE_DATATYPE_BYTEARRAY);
  if (htsMeasureCharId == 0) {
    error(F("Could not add Temperature characteristic"));

  /* Add the Health Thermometer Service to the advertising data (needed for Nordic apps to detect the service) */
  Serial.print(F("Adding Health Thermometer Service UUID to the advertising payload: "));
  uint8_t advdata[] { 0x02, 0x01, 0x06, 0x05, 0x02, 0x09, 0x18, 0x0a, 0x18 };
  ble.setAdvData( advdata, sizeof(advdata) );

  /* Reset the device for the new service setting changes to take effect */
  Serial.print(F("Performing a SW reset (service changes require a reset): "));


/** Send randomized heart rate data continuously **/
void loop(void)
  double temp = random(0, 100) / 10.0;

  Serial.print(F("Updating Temperature value to "));
  Serial.println(F(" Fahrenheit"));

  // Chars value is 1 flag + 4 float value. Tempearature is in Fahrenheit unit
  uint8_t temp_measurement [5] = { bit(0) };
  float2IEEE11073(temp, temp_measurement+1);

  // TODO temperature is not correct due to Bluetooth use IEEE-11073 format
  gatt.setChar(htsMeasureCharId, temp_measurement, 5);

  /* Delay before next measurement update */

Attached is a picture of my App Inventor block code. I basically just need to figure out the UUID’s that I should type there in conjunction with the service and char UUID’s I set in the Arduino code.

Right now I can get the app to connect to the BLE (the blue light on the nRF module turns on when I connect), but the data isn’t getting through because the settings aren’t right. There are examples with CurieBLE using the Arduino 101 and that works because the Arduino code explicitly adds the full service and characteristic UUID’s up front. However, here with the nRF51 I’m not sure how to add the full UUID like that.

Any ideas? I feel like I’m really close to getting this to work but can’t get this last part figured out! Thanks in advance!