Read notify characteristic value sample needed

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chris mcilvoy

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Jan 20, 2017, 3:17:34 PM1/20/17

to web-bluetooth

Following the Chrome samples need help reading characteristic value 0x2A34.

Currently receiving message:

Argh! NotFoundError: User cancelled the requestDevice() chooser.

[code]

let filters = [];
    filters.push({services: ['glucose']});
    // filters.push({name: filterName});
    // filters.push({namePrefix: filterNamePrefix});

    log('Requesting Bluetooth Device...');
    navigator.bluetooth.requestDevice({filters: filters})

  .then(device => {
    log('Connecting to GATT Server...');
    return device.gatt.connect();
  })
  .then(server => {
    log('Getting Service...');
    return server.getPrimaryService('glucose');
  })

  .then(service => {
    log('Getting Characteristics...');
    s = service
    // 00002a51-0000-1000-8000-00805f9b34fb
    // 00002a52-0000-1000-8000-00805f9b34fb
    // 00002a34-0000-1000-8000-00805f9b34fb
    // 00002a18-0000-1000-8000-00805f9b34fb
    console.log(service)
      return service.getCharacteristic('glucose_measurement');
    // Get all characteristics.
    // return service.getCharacteristics();
  })
  .then(characteristic => {
    c = characteristic;
    console.log(c)
    return characteristic.readValue();
  })

[/code]

Also tried getting value int he callback on but no luck. 
[code]

.then(characteristic => {
    c = characteristic;
    console.log(c)

    return c.startNotifications().then(_ => {
      log('> Notifications started');
      c.addEventListener('characteristicvaluechanged',
          handleNotifications);
    });
  })

[/code]

Vincent Scheib

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Jan 20, 2017, 4:25:29 PM1/20/17

to chris mcilvoy, web-bluetooth

The requestDevice is being called, but is rejecting it's promise with nothing found. You should be seeing a chooser UI appear -- but then are you not seeing any local devices and must cancel the chooser?

What platform are you on?

This page has info for collecting logs

https://www.chromium.org/developers/how-tos/file-web-bluetooth-bugs

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chris mcilvoy

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Jan 20, 2017, 5:46:02 PM1/20/17

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I am able to get the device (see image) and also get characteristic 00002a51.

Platform: mac sierra, Chrome Version 55.0.2883.95 (64-bit)

I am wondering if there is something unique about this characteristic since if is notify property.

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Jeffrey Yasskin

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Jan 20, 2017, 6:14:33 PM1/20/17

to chris mcilvoy, web-bluetooth

If the characteristic's properties only include the Notify bit and not the Read bit, then .readValue() is expected to return Not Supported, since the properties say it's not supported.

https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.bluetooth.service.glucose.xml says this is the case for glucose_measurement.

Sorry,

Jeffrey

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chris mcilvoy

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Jan 20, 2017, 6:44:59 PM1/20/17

to web-bluetooth

Thanks for the reply. Yes I figured that was the case. What is the recommendation for getting values, meaning how can I listen for notifications and also trigger events so I can get callback? Is there a sample of something like this? Thanks!

Jeffrey Yasskin

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Jan 20, 2017, 6:48:07 PM1/20/17

to chris mcilvoy, web-bluetooth

Probably https://github.com/WebBluetoothCG/demos/tree/gh-pages/heart-rate-sensor, which also involves a notification-only characteristic.

On Fri, Jan 20, 2017 at 3:44 PM, chris mcilvoy <cmci...@gmail.com> wrote:

Thanks for the reply. Yes I figured that was the case. What is the recommendation for getting values, meaning how can I listen for notifications and also trigger events so I can get callback? Is there a sample of something like this? Thanks!

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chris mcilvoy

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Jan 23, 2017, 8:06:24 AM1/23/17

to Jeffrey Yasskin, web-bluetooth

Thanks for your response. These samples are great reference.

Here is Java code we have to write to the Record Access Control characteristic:

byte opCode = 0x000000ff & 1;

byte operator = 0x000000ff & 1;

byte[] racpData = new byte[1/* opcode */+ 1 /* operator */];

racpData[0] = opCode;

racpData[1] = operator;

writeCharacteristic(...);

Our Javascript code is returning "Uncaught (in promise) DOMException: GATT operation failed for unknown reason.":
service = glucose

characteristic = 0x2A52

var racpData = new Uint8Array([0x01,0x01]);

let opCode = 0x000000ff & 1;

let operator = 0x000000ff & 1;

racpData[0] = opCode;

racpData[1] = operator;

this._writeCharacteristicValue(0x2A52, racpData);

Let me know if something looks incorrect. Thanks.

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Vincent Scheib

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Jan 23, 2017, 2:19:28 PM1/23/17

to chris mcilvoy, Jeffrey Yasskin, web-bluetooth

I don't see anything wrong on the call to write. What has happened just before this? connect, getPrimaryService, getCharacteristic, and then the first writeValue fails?

E.g. can you write & share code similar to https://googlechrome.github.io/samples/web-bluetooth/reset-energy.html ? System logs will provide more details of what is failing https://www.chromium.org/developers/how-tos/file-web-bluetooth-bugs

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François Beaufort 🇫🇷

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Jan 24, 2017, 10:07:07 AM1/24/17

to Vincent Scheib, chris mcilvoy, Jeffrey Yasskin, web-bluetooth

For what I understand reading http://stackoverflow.com/a/25056182/422957, it looks like you would need something like this below. Note that I didn't test it though ;)

var glucoseMeasurementCharacteristic, racpCharacteristic;

navigator.bluetooth.requestDevice({filters: [{services: ['glucose']}]})

.then(device => device.gatt.connect())

.then(server => server.getPrimaryService('glucose'))

.then(service => {

return Promise.all([

service.getCharacteristic('glucose_measurement'),

service.getCharacteristic('record_access_control_point')

])

})

.then(characteristics => {

[glucoseCharacteristic, racpCharacteristic] = characteristics;

})

.then(_ => glucoseCharacteristic.startNotifications())

.then(_ => glucoseCharacteristic.addEventListener('characteristicvaluechanged', handleGlucose))

.then(_ => racpCharacteristic.startNotifications())

.then(_ => racpCharacteristic.addEventListener('characteristicvaluechanged', handleRacp))

.then(_ => racpCharacteristic.writeValue(new Uint8Array([1, 1])))

.catch(error => {

console.log(error);

});

function handleGlucose(event) {

console.log(event.target.value);

}

function handleRacp(event) {

console.log(event.target.value);

}

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chris mcilvoy

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Jan 25, 2017, 8:47:27 AM1/25/17

to François Beaufort 🇫🇷, Vincent Scheib, Jeffrey Yasskin, web-bluetooth

Thanks so much. I am testing today with the glucometer. I am wanted to set up the proper logging however zsh is complaining about the vmodule flag. Any thoughts?

/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --enable-logging=stderr --vmodule=*bluetooth*=9 --enable-web-bluetooth

zsh: no matches found: --vmodule=*bluetooth*=9

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Jeffrey Yasskin

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Jan 25, 2017, 11:40:59 AM1/25/17

to chris mcilvoy, scheib, web-bluetooth, François Beaufort 🇫🇷

Put single quotes around that argument.

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chris mcilvoy

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Jan 25, 2017, 9:14:57 PM1/25/17

to Jeffrey Yasskin, scheib, web-bluetooth, François Beaufort 🇫🇷

Thanks everyone for the comments.

I get this exception in the Chrome console:

DOMException: GATT operation failed for unknown reason.

Here is the log output from Chrome:

[6206:775:0125/211111:VERBOSE1:bluetooth_discovery_session.cc(45)] Stopping device discovery session.

[6206:775:0125/211111:VERBOSE1:bluetooth_low_energy_discovery_manager_mac.mm(80)] StopDiscovery

[6206:775:0125/211111:VERBOSE1:bluetooth_allowed_devices_map.cc(28)] Adding a device to Map of Allowed Devices.

[6206:775:0125/211111:VERBOSE1:bluetooth_allowed_devices_map.cc(46)] Id generated for device: kHPzcr+1gtCzkKvipYYdYQ==

[6206:775:0125/211111:VERBOSE1:web_bluetooth_service_impl.cc(783)] Device: NiproBGM

[6206:775:0125/211111:VERBOSE1:web_bluetooth_service_impl.cc(784)] UUIDs:

[6206:775:0125/211111:VERBOSE3:bluetooth_adapter.cc(386)] device: A4:30:62:E0:02:5C, last_update: 2017-01-26 02:11:11.177 UTC, exp: 0

[6206:775:0125/211111:VERBOSE3:bluetooth_adapter.cc(386)] device: 70:50:B1:31:2F:7D, last_update: 2017-01-26 02:11:11.507 UTC, exp: 0

[6206:775:0125/211111:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 04:4B:ED:E9:40:04

[6206:775:0125/211111:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 1C:1A:C0:F0:30:DB

[6206:775:0125/211111:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 20:3C:AE:D3:3C:05

[6206:775:0125/211111:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 9C:35:83:04:20:8C

[6206:775:0125/211111:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 34:15:9E:CC:F5:F1

[6206:775:0125/211111:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 20:AB:37:E7:17:7D

[6206:775:0125/211111:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 70:70:0D:15:DF:A3

[6206:775:0125/211111:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 6C:70:9F:BB:3B:32

[6206:775:0125/211112:VERBOSE3:bluetooth_adapter.cc(386)] device: A4:30:62:E0:02:5C, last_update: 2017-01-26 02:11:11.177 UTC, exp: 0

[6206:775:0125/211112:VERBOSE3:bluetooth_adapter.cc(386)] device: 70:50:B1:31:2F:7D, last_update: 2017-01-26 02:11:11.507 UTC, exp: 0

[6206:775:0125/211112:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 04:4B:ED:E9:40:04

[6206:775:0125/211112:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 1C:1A:C0:F0:30:DB

[6206:775:0125/211112:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 20:3C:AE:D3:3C:05

[6206:775:0125/211112:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 9C:35:83:04:20:8C

[6206:775:0125/211112:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 34:15:9E:CC:F5:F1

[6206:775:0125/211112:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 20:AB:37:E7:17:7D

[6206:775:0125/211112:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 70:70:0D:15:DF:A3

[6206:775:0125/211112:VERBOSE3:bluetooth_adapter_mac.mm(468)] Updating classic device: 6C:70:9F:BB:3B:32