Inject GATT descriptors #29

svogl · 2019-10-11T07:09:14Z

We have a number of known BLE devices the we (re-)connect to often. Speeding up the connection setup phase is good for the user experience (less delay, less potential for packet loss), so we have extended noble a little to report the GATT data structures for services and characteristics and to initialize its inner workings with this data.

In order to not change default behavour, there are two new events one can listen for when discovering GATT entries, simply register them before the actual discovery call:

 peripheral.on('servicesDiscovered', (peripheral, services) => { ... }
 service.on('characteristicsDiscovered', (characteristics) => {...}

returns an array of services resp. characteristics including low-level information that can be used to initialize noble:

 const servs = [
        { "startHandle": 1, "endHandle": 4, "uuid": "1801" },
        { "startHandle": 5, "endHandle": 9, "uuid": "1800" },
        { "startHandle": 10, "endHandle": 29, "uuid": "180a" }]
 let serviceObjs =  noble.addServices(peripheralUuid, servs)

 const enviroChara = [
  { "startHandle": 53, "properties": 18, "valueHandle": 54, "uuid": "2a6d", "propsDecoded": ["read", "notify"], "rawProps": 18, "endHandle": 57 },
  { "startHandle": 58, "properties": 18, "valueHandle": 59, "uuid": "2a6e", "propsDecoded": ["read", "notify"], "rawProps": 18, "endHandle": 62 }]

 let characteristicsObjs = noble.addCharacteristics(peripheral.uuid, enviroService.uuid, enviroChara);

addServices returns an array of service objects, addCharacteristics an array of Characteristic objects that can be used to discover, subscribe for data etc.

rzr · 2019-10-11T08:00:11Z

Thanks, can you try to split this change set into several pull requests on upstream too ?
Then update commit messages with "Forwarded: $url" meta info

Reviewers welcome too

mrstegeman

Thoughts:

I don't care for the naming of the new events. It seems like the original events were just misspelled, so adding these new events with the names the originals should have had is confusing. Why not just add the service/characteristic objects as additional data to the existing events? That should retain backwards compatibility while being more clear.
Can you update the README and maybe add an example in examples/?
It seems strange for a developer to have to reinitialize an object manually. Is there a way that noble could (optionally) cache these data structures internally, rather than forcing the developer to hold on to internal objects they can't do much with?

svogl · 2019-10-17T10:54:25Z

Thanks for your thoughts @mrstegeman, let me add my own:

I don't care either, so if you have suggestions ( gatt.serviceDisvover? ) head on. I did not add it the original reasons as this is implementation specific (not every backend might expose it) and it is not necessary for normal operation, bloating objects and potentially causing confusion for normal app developers
will add something later, sure
Caching would be ideal, of course, but depends on the use-case; some devices change their GATT-descriptions on the fly for example, so this is a non-trivial subsystem on its own. We just wanted to get one (our) use case solved so other people can pick up work from here.
S

rzr · 2019-10-21T13:16:35Z

examples/cache-gatt-reconnect.js

+  }
+  console.log()
+
+  let temperatureChara = undefined


is it well named ?

rzr

Maybe it would be better to have all temperature related code into a separate file ?

Please also submit upstream 1st

svogl · 2019-10-21T14:12:42Z

Maybe it would be better to have all temperature related code into a separate file ?

I intended to write a small but functional example. I don't think the effort of extracting 7 lines or so is worth a separate file. The point here is the difference in timing of the same task under different conditions (with cache / without).

Please also submit upstream 1st

I'm commiting to my fork which you are seeing automatically. This is fine for me, esp. as this allows you and others to comment here. I'd like to push an agreed-upon version upstream and not double work on every commit.

rzr · 2019-10-22T09:51:30Z

I suggested to isolate temperature in separate place to make it scalable for other types...

svogl · 2019-10-22T10:25:09Z

Well then let me suggest to use an environment variable, that way you can change it on the fly, as in
SENSOR='Pressure' node cache-gatt-discovery.js

If you have something else in mind, suggestion welcome :)

rzr · 2019-10-28T13:57:51Z

examples/cache-gatt-discovery.js

@@ -88,7 +94,7 @@ let findServices = function (noble, peripheral) {

  peripheral.discoverServices([], (error, services) => {

-    let temperatureCharacteristic = undefined
+    let sensorCharacteristic = undefined


should this be set explicitly ?

rzr · 2019-10-28T13:58:25Z

examples/cache-gatt-discovery.js

@@ -8,7 +8,13 @@
 var noble = require('../index');
 const fs = require('fs'); 

+// the sensor value to scan for, number of bits and factor for displaying it
+const CHANNEL = process.env['CHANNEL'] ? process.env['CHANNEL'] : 'Temperature'


or just "Unknown"

I'd prefer a working example... at least for parts of the universe ;)

rzr

I like this, what about other reviewers ?

readeral · 2019-11-14T10:37:06Z

Seems excellent - anything else holding this back?

rzr · 2019-11-14T11:47:29Z

Unless there is any negative feedback I can merge this next month

cc: @mrstegeman, @gfwilliams

also @readeral have you considered to join the abandonware co-maintainers team see

https://abandonware.github.io/

mrstegeman · 2019-11-14T16:43:21Z

My primary request at this point is that the README is updated with the new events and APIs.

…ered, characteristicsDiscovered) that enables caching of gatt information. The cached objects can be used to initialize a device via addServices() and addCharacteristics(), which return an array of Noble objects ready for connecting in the usual way. examples/cache-gatt-discovery.js provides an example for collecting GATT data and persisting the information, examples/cache-gatt-reconnect.js uses the data to connect to the device using the cached data.

rzr · 2020-01-15T10:56:01Z

Please review other PR then I plan to release something in a couple of weeks

(serviceDiscovered, characteristicsDiscovered) that enables caching of gatt information. The cached objects can be used to initialize a device via addServices() and addCharacteristics(), which return an array of Noble objects ready for connecting in the usual way. examples/cache-gatt-discovery.js provides an example for collecting GATT data and persisting the information, examples/cache-gatt-reconnect.js uses the data to connect to the device using the cached data. Author: Simon Vogl <simon@voxel.at> Relate-to: #29 Change-Id: I68bc5208529f872e5f60d7c0315a6346d24df2fb

pursual · 2020-09-09T02:44:48Z

The mac bindings do not call characteristicsDiscovered. They also do not have this._bindings.addCharacteristics or this._bindings.addServices

(serviceDiscovered, characteristicsDiscovered) that enables caching of gatt information. The cached objects can be used to initialize a device via addServices() and addCharacteristics(), which return an array of Noble objects ready for connecting in the usual way. examples/cache-gatt-discovery.js provides an example for collecting GATT data and persisting the information, examples/cache-gatt-reconnect.js uses the data to connect to the device using the cached data. Author: Simon Vogl <simon@voxel.at> Relate-to: abandonware#29 Change-Id: I68bc5208529f872e5f60d7c0315a6346d24df2fb

(serviceDiscovered, characteristicsDiscovered) that enables caching of gatt information. The cached objects can be used to initialize a device via addServices() and addCharacteristics(), which return an array of Noble objects ready for connecting in the usual way. examples/cache-gatt-discovery.js provides an example for collecting GATT data and persisting the information, examples/cache-gatt-reconnect.js uses the data to connect to the device using the cached data. Author: Simon Vogl <simon@voxel.at> Relate-to: #29 Change-Id: I68bc5208529f872e5f60d7c0315a6346d24df2fb

This was referenced Oct 11, 2019

GATT data caching #27

Closed

Enable caching of GATT characteristics noble/noble#908

Open

mrstegeman suggested changes Oct 11, 2019

View reviewed changes

rzr reviewed Oct 21, 2019

View reviewed changes

examples/cache-gatt-reconnect.js Outdated

}

console.log()

let temperatureChara = undefined

Copy link

rzr Oct 21, 2019

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

is it well named ?

rzr reviewed Oct 21, 2019

View reviewed changes

rzr reviewed Oct 28, 2019

View reviewed changes

svogl force-pushed the inject-gatt-descriptors branch from f1cc0e4 to ed5fc14 Compare December 17, 2019 07:55

rzr merged commit 0d15d19 into abandonware:master Jan 15, 2020

svogl deleted the inject-gatt-descriptors branch January 18, 2020 15:35

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Inject GATT descriptors #29

Inject GATT descriptors #29

svogl commented Oct 11, 2019

rzr commented Oct 11, 2019

mrstegeman left a comment

svogl commented Oct 17, 2019

rzr Oct 21, 2019

rzr left a comment

svogl commented Oct 21, 2019

rzr commented Oct 22, 2019

svogl commented Oct 22, 2019

rzr Oct 28, 2019

rzr Oct 28, 2019

svogl Oct 28, 2019

rzr left a comment

readeral commented Nov 14, 2019

rzr commented Nov 14, 2019

mrstegeman commented Nov 14, 2019

rzr commented Jan 15, 2020

pursual commented Sep 9, 2020

Inject GATT descriptors #29

Inject GATT descriptors #29

Conversation

svogl commented Oct 11, 2019

rzr commented Oct 11, 2019

mrstegeman left a comment

Choose a reason for hiding this comment

svogl commented Oct 17, 2019

rzr Oct 21, 2019

Choose a reason for hiding this comment

rzr left a comment

Choose a reason for hiding this comment

svogl commented Oct 21, 2019

rzr commented Oct 22, 2019

svogl commented Oct 22, 2019

rzr Oct 28, 2019

Choose a reason for hiding this comment

rzr Oct 28, 2019

Choose a reason for hiding this comment

svogl Oct 28, 2019

Choose a reason for hiding this comment

rzr left a comment

Choose a reason for hiding this comment

readeral commented Nov 14, 2019

rzr commented Nov 14, 2019

mrstegeman commented Nov 14, 2019

rzr commented Jan 15, 2020

pursual commented Sep 9, 2020