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Topic: Nano BLE, Central cant read values (Read 49 times) previous topic - next topic

MoeGer

Nov 11, 2019, 08:24 pm Last Edit: Nov 11, 2019, 08:27 pm by MoeGer Reason: Had to insert the image from the attachment
Hi everyone,

I recently bought a nano 33 ble and wanted to test out its BLE capabilities, the receiving/sending advertising data works fine.


Now I would like to use the nano as peripheral and set up a service with a readable characteristic.
I used the peripheral examples (battery monitor, button led, led) but always had the following problem:

When I connect my smartphone to the nano (with nRF connect) I can see the characteristic but I cant read the values.

Here is an example code I wrote and what I see on the nRF connect.

Code: [Select]

#include <ArduinoBLE.h>

// BLE Battery Service
BLEService batteryService("180F");

// BLE Battery Level Characteristic
BLEUnsignedCharCharacteristic batteryLevelChar("2A19",  // standard 16-bit characteristic UUID
    BLERead ); // remote clients will be able to get notifications if this characteristic changes

int oldBatteryLevel = 1;  


void setup() {

  // begin initialization
  if (!BLE.begin()) {
    Serial.println("starting BLE failed!");
    while (1);
  }

  BLE.setLocalName("BatteryMonitor");
  BLE.setAdvertisedService(batteryService); // add the service UUID
  batteryService.addCharacteristic(batteryLevelChar); // add the battery level characteristic
  BLE.addService(batteryService); // Add the battery service
  batteryLevelChar.writeValue(oldBatteryLevel); // set initial value for this characteristic

  BLE.advertise();
}

void loop() {
  BLEDevice central = BLE.central();
  if (central) {
    while (central.connected()) {
    }
  }
}


And here is what I see at the nRF connect (or any other app) after connection.



I really hope I am missing something (obvious). Any help would be greatly appriciated!

Moritz


RudolfAtRTC

You have reduced the example too much!
In your loop() the most important statement - sensing and sending the battery status is not present.

Please use the example in its original state - and then modify it!

MoeGer

Hi,

thanks for the answer.

I just checked with the examples in original state again and the problem still persists.

Here is the code from the battery example I used.

Code: [Select]

/*
  Battery Monitor

  This example creates a BLE peripheral with the standard battery service and
  level characteristic. The A0 pin is used to calculate the battery level.

  The circuit:
  - Arduino MKR WiFi 1010, Arduino Uno WiFi Rev2 board, Arduino Nano 33 IoT,
    Arduino Nano 33 BLE, or Arduino Nano 33 BLE Sense board.

  You can use a generic BLE central app, like LightBlue (iOS and Android) or
  nRF Connect (Android), to interact with the services and characteristics
  created in this sketch.

  This example code is in the public domain.
*/

#include <ArduinoBLE.h>

 // BLE Battery Service
BLEService batteryService("180F");

// BLE Battery Level Characteristic
BLEUnsignedCharCharacteristic batteryLevelChar("2A19",  // standard 16-bit characteristic UUID
    BLERead | BLENotify); // remote clients will be able to get notifications if this characteristic changes

int oldBatteryLevel = 0;  // last battery level reading from analog input
long previousMillis = 0;  // last time the battery level was checked, in ms

void setup() {
  Serial.begin(9600);    // initialize serial communication
  while (!Serial);

  pinMode(LED_BUILTIN, OUTPUT); // initialize the built-in LED pin to indicate when a central is connected

  // begin initialization
  if (!BLE.begin()) {
    Serial.println("starting BLE failed!");

    while (1);
  }

  /* Set a local name for the BLE device
     This name will appear in advertising packets
     and can be used by remote devices to identify this BLE device
     The name can be changed but maybe be truncated based on space left in advertisement packet
  */
  BLE.setLocalName("BatteryMonitor");
  BLE.setAdvertisedService(batteryService); // add the service UUID
  batteryService.addCharacteristic(batteryLevelChar); // add the battery level characteristic
  BLE.addService(batteryService); // Add the battery service
  batteryLevelChar.writeValue(oldBatteryLevel); // set initial value for this characteristic

  /* Start advertising BLE.  It will start continuously transmitting BLE
     advertising packets and will be visible to remote BLE central devices
     until it receives a new connection */

  // start advertising
  BLE.advertise();

  Serial.println("Bluetooth device active, waiting for connections...");
}

void loop() {
  // wait for a BLE central
  BLEDevice central = BLE.central();

  // if a central is connected to the peripheral:
  if (central) {
    Serial.print("Connected to central: ");
    // print the central's BT address:
    Serial.println(central.address());
    // turn on the LED to indicate the connection:
    digitalWrite(LED_BUILTIN, HIGH);

    // check the battery level every 200ms
    // while the central is connected:
    while (central.connected()) {
      long currentMillis = millis();
      // if 200ms have passed, check the battery level:
      if (currentMillis - previousMillis >= 200) {
        previousMillis = currentMillis;
        updateBatteryLevel();
      }
    }
    // when the central disconnects, turn off the LED:
    digitalWrite(LED_BUILTIN, LOW);
    Serial.print("Disconnected from central: ");
    Serial.println(central.address());
  }
}

void updateBatteryLevel() {
  /* Read the current voltage level on the A0 analog input pin.
     This is used here to simulate the charge level of a battery.
  */
  int battery = analogRead(A0);
  int batteryLevel = map(battery, 0, 1023, 0, 100);

  if (batteryLevel != oldBatteryLevel) {      // if the battery level has changed
    Serial.print("Battery Level % is now: "); // print it
    Serial.println(batteryLevel);
    batteryLevelChar.writeValue(batteryLevel);  // and update the battery level characteristic
    oldBatteryLevel = batteryLevel;           // save the level for next comparison
  }
}


I can connect to the board, but after that the values still can not be read.


RudolfAtRTC

OK - your original program example works with my phone:
 - Android 6.0
 - nRF Connect 4.22.3

Additional to your phone I see a block "Battery Service" with some expected values.

May be, you should update your nRF app?

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