Problem reading value from a Nano 33 BLE Sense

Official Hardware Nano Family Nano 33 BLE Sense
1

Hello,
This message was also posted on the Networks sub-boards. Being a beginner with Arduino, I try my few sketches, and I am currently facing a problem when trying to read a dummy value sent through bluetooth. Here is the sketch adapted from a LED example:

#include <ArduinoBLE.h>

BLEService ledService("19B10000-E8F2-537E-4F6C-D104768A1214"); // BLE LED Service

BLEByteCharacteristic fooCharacteristic("19B10001-E8F2-537E-4F6C-D104768A1214", BLERead | BLEWrite );


const int ledPin = LED_BUILTIN; // pin to use for the LED

void setup() {
  Serial.begin(9600);
  while (!Serial);

  // set LED pin to output mode
  pinMode(ledPin, OUTPUT);

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

    while (1);
  }

  // set advertised local name and service UUID:
  BLE.setLocalName("LED");
  BLE.setAdvertisedService(ledService);

  // add the characteristic to the service
  ledService.addCharacteristic(fooCharacteristic);

  // add service
  BLE.addService(ledService);
  
  // start advertising
  BLE.advertise();

  Serial.println("BLE LED Peripheral");
}

void loop() {
  // listen for BLE peripherals to connect:
  BLEDevice central = BLE.central();
  float testfloat = 3.14152;
  
  // if a central is connected to peripheral:
  if (central) {
    Serial.print("Connected to central: ");
    // print the central's MAC address:
    Serial.println(central.address());
    
    // while the central is still connected to peripheral:
    while (central.connected()) {
      fooCharacteristic.writeValue((byte)testfloat);
    }

    // when the central disconnects, print it out:
    Serial.print(F("Disconnected from central: "));
    Serial.println(central.address());
  }
}

With this on the device, I can connect with gatttool on linux.

hms@joe:~/projects/arduino$ gatttool -I
[                 ][LE]> connect fc:57:4a:cb:ea:2e
Attempting to connect to fc:57:4a:cb:ea:2e
Connection successful
[fc:57:4a:cb:ea:2e][LE]> char-read-uuid 19B10001-E8F2-537E-4F6C-D104768A1214
Error: Read characteristics by UUID failed: Attribute PDU was invalid
[fc:57:4a:cb:ea:2e][LE]>

And so there is this error:

Error: Read characteristics by UUID failed: Attribute PDU was invalid

I can connect with LightBlue from Android, read a value, but it appears that the hex on binary value that is read does not correspond to the value that is written by the device.
What am I doing wrong here? Can it be a problem with my laptop (and me being dumb at reading the value on LightBlue)?
Thanks for yout help!

2

Please don't do that. It is called cross posting and forbidden by the forum rules to avoid wasting time of multiple users that try to help.

I read 0x03 in the LightBlue app, which is what I would expect.

Additionally, I would recommend the following two changes.

  • Do not write to the characteristic in a tight loop, e.g. use a millis() timer to limit the update rate.

  • Initialize the characteristics with a value before you start advertising.

3

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