Develop Reference

How to use an android device as a matter sensor?

I have an android device running a custom ROM and self-developed apps.
Android version: 8.1 (API level 27)
There is a temperature and humidity sensor built into the android device. Now I want to feed the sensor data into my smart home system using Matter.
I´m not familiar with C++ and other languages apart from Java/Kotlin and Python. So is there any way to send the sensor data to my Amazon Echo Smart Home Hub via the Android software with Matter?
It would also be good if it could work independently of the Smart Home system (Google, Apple, Samsung, etc.).
I have checked out the Matter Github repository. There are some example apps and I tried to apply it to my issue. But I did not get any further at this point.
Any help is much appreciated.

An android app might not be the best path for this, as it cannot stay on and listen to external communications all the time. You can look for solutions to run a local server on the android system and implement a virtual device that way. Also, you can download the matter specification from the CSA website https://csa-iot.org/all-solutions/matter/ and take a look at how to implement matter communications.

Bluetooth Low Energy application in Visual Studio C++ for image sharing. Which tools should I use?

I'm trying to develop a C++ application on Windows 10 (using Visual Studio 2017) capable of looking for nearby mobile devices and sending data (images) via Bluetooth. I'm new to Bluetooth applications, but from what I understand, the best solution is to use BLE and make the computer a GATT server.
For this purpose, I'm quite confused about which tool I should use in order to start creating my application, since most of the libraries I have found online are outdated or poorly documented (libblepp, gattlibpp, bluetoe).
I've also found this Windows API but I don't understand if this is what I should use and I don't know how to include it in my project neither.
Has anybody had some experience with this and could provide me some hints concerning the right tool to use, in order to get started with my project?
On the other side, I would like to develop a mobile app using Flutter capable of receiving the image and reading the data sent by the computer. flutter_blue looks like the best option to go with.
Edit: The idea for the application is the following: the computer runs an application that generates various frames. In the meanwhile, it constantly scans for nearby devices and, whenever a user makes a request, it sends the current output image to the device that makes the request.

The Windows API is what you should use if you write a C++ application for Windows. That will be the best supported option. If you happen to find some library that also does BLE it will probably just be a wrapper around the Windows API.
Unfortunately these APIs use the WinRT architecture which is not the easiest to set up but should work fine once you've managed to set up the environment.

Transfer data between iOS and Android via Bluetooth?

I've been reading up on how to transfer data between iOS devices over Bluetooth using GameKit. I'm not writing a game, per se, but do have a need to transfer a small amount of binary data between two devices. Between two iOS devices, this is easy enough. However, I was wondering if it is possible to transfer data between an iOS device and an Android device via the same mechanism.
Has anyone come across documentation/tutorial that would explain how to do this? Is it even technically possible? Or has Apple put in some sort of restriction that would prevent this?
The other option I discovered was Bonjour over Bluetooth. Would this be a more suitable option for this type of operation?

This question has been asked many times on this site and the definitive answer is: NO, you can't connect an Android phone to an iPhone over Bluetooth, and YES Apple has restrictions that prevent this.
Some possible alternatives:
Bonjour over WiFi, as you mentioned. However, I couldn't find a comprehensive tutorial for it.
Some internet based sync service, like Dropbox, Google Drive, Amazon S3. These usually have libraries for several platforms.
Direct TCP/IP communication over sockets. (How to write a small (socket) server in iOS)
Bluetooth Low Energy will be possible once the issues on the Android side are solved (Communicating between iOS and Android with Bluetooth LE)
Coolest alternative: use the Bump API. It has iOS and Android support and really easy to integrate. For small payloads this can be the most convenient solution.
Details on why you can't connect an arbitrary device to the iPhone. iOS allows only some bluetooth profiles to be used without the Made For iPhone (MFi) certification (HPF, A2DP, MAP...). The Serial Port Profile that you would require to implement the communication is bound to MFi membership. Membership to this program provides you to the MFi authentication module that has to be added to your hardware and takes care of authenticating the device towards the iPhone. Android phones don't have this module, so even though the physical connection may be possible to build up, the authentication step will fail. iPhone to iPhone communication is possible as both ends are able to authenticate themselves.

Maybe a bit delayed, but technologies have evolved since so there is certainly new info around which draws fresh light on the matter...
As iOS has yet to open up an API for WiFi Direct and Multipeer Connectivity is iOS only, I believe the best way to approach this is to use BLE, which is supported by both platforms (some better than others).
On iOS a device can act both as a BLE Central and BLE Peripheral at the same time, on Android the situation is more complex as not all devices support the BLE Peripheral state. Also the Android BLE stack is very unstable (to date).
If your use case is feature driven, I would suggest to look at Frameworks and Libraries that can achieve cross platform communication for you, without you needing to build it up from scratch.
For example: http://p2pkit.io or google nearby
Disclaimer: I work for Uepaa, developing p2pkit.io for Android and iOS.

You could use p2pkit, or the free solution it was based on: https://github.com/GitGarage. Doesn't work very well, and its a fixer-upper for sure, but its, well, free. Works for small amounts of data transfer right now.

Rhomobile, BLE112 Bluetooth device - iOS and android app

I have been searching for a while now and decided to post a question here to see if someone had already traveled down this specific road.
I am developing a bluetooth enabled device, using the Bluegiga BLE112 chip. They announce this chip to be easily used with iOS devices (and this was our main reason for choosing it)
The device will need to communicate with an App, that we need to be developed for iOS, Android, Windows Phone, and Blackberry. Due to this need, I've decided to use Rhomobile, as it seems to be the only one that supports developing BT apps for iOS without having to develop further plugins.
I only need to send small messages (like commands, small strings) and sometimes a bigger file to the device's internal memory.
On Rhomobile's BT documentation, they state that for iOS it is only possible to comunicate between iOS devices ( i'm thinking that they say this because of the MiFi limitations imposed by Apple, but that using Bluegigas chip are not a problem...)
My question is:
Since Bluegiga's documentation has examples of devices communicating with iOS using their chip, i should be able to develop using Rhomobile and not suffer from the limitation stated above. I wanted to be as sure as possible before making my company spend money ordering the chips and development board and what not..
Has anyone tried this, is my thinking missing something?
Thank you all for your time.
Daniel

Good Question, I think I can understand the reason for your confusion.
The main reason is many people/products/frameworks does not clearly mention if they are talking about Bluetooth Classic or Bluetooth Low Energy (BLE).
These are both 2 different things and even thougfh they are called "Bluetooth" one cannot talk to the other.
(Some devices can be both Classic and Bluetooth Low Energy, which allows it to connect to either types)
Ok now comming to your Question :
THE bluegiga dongle is BLE
The Rhomobile is refering to the Bluetooth Classic version of the API.
On iOS the BLE APIs are open to applications, but Classic is limited on iOS , one way for Apps to use Classic Bluetooth on iOS is via the Gamekit APIs but that is possible only when talking with iOS devices, so it wont connect to another Android or Win device that is also Classic.
Needless to say with BLE APIs you cannot connect to calssic anyways.
The bluegiga examples are BLE examples, and apple also has good documentation and examples / samples on how to use BLE so yes it is easy to build a device and app using BLE on iOS.
There is nothing special abut any particular chip yo ucan use any BLE chip - there are many vendors today.
BUT Android (and I guess Windows as well) does not yet have BLE APIs for applications to use :( (Bit I think is is comming soon :))
So I hope this clears things up a bit.

How widely supported is the accelerometer in Android devices?

We're developing an Android app that relies on the accelerometer for certain features. I'm wondering how safe it is to rely on the existence of the accelerometer and not provide alternative UI options for devices that do not support it (e.g. a button). My observation is that most "smartphone" Androids out there support it. Am I correct?
It would be nice if someone can point me to some data or stats for all Android devices out there.

I've personally never seen an android device without an accelerometer. The internet seems to agree on that aswell:
Link 1
Link 2