Bluetooth Detector

[1446406]

I'm trying to create a Bluetooth detector for a school project that will emit a beeping noise when a specific Bluetooth module is NOT detected. Is this even possible?

[1446406]

Specifically, I want to use if/then logic to test if a specific Bluetooth device is connected

[Chris Ward]

Hi

There is a difference between being detected and being connected - you could detect (find) a device, but be unable to connect to it.

Based on that, what do you actually need to do?

[1446406]

So what I want to do is connect to a bluetooth device, and then whenever that device is not in range I get an indicator

[Chris Ward]

OK - when out of range, the connection is lost. In App Inventor that can be detected and then any type of indication can be made - sound, pop-up message, phone vibrate.

[1446406]

Sorry if this is asking too much, but how exactly would I detect that?

[Chris Ward]

Ok, Bluetooth Classic and BLE have similar Blocks to check that the Android Device (phone) is connected. If the connection is lost, then "IsConnected" returns "False".

Here is an example where an App periodically receives data from a microcontroller. If the connection is lost, the phone is vibrated:

[1446406]

is this testing for a Bluetooth connection in general or for a specific device? And could I use this same block setup to test for a BlueTooth connection?

[Chris Ward]

Hi

The Block checks the connection to a previously selected device, then checks if data is available to receive.

Before that, a List of available devices detected is collated and the User selects which device to connect to from that List.

[1446406]

I already have a block setup that connects to a selected BlueTooth device, will this work together?

[1446406]

Also when you say micro-controller does that mean the device containing the BlueTooth module?

[1446406]

And with a shorter time interval for the clock will that make it so that the system does checks more often?

[Chris Ward]

Hi

Yes they will, but, in your ListPicker 1 AfterPicking Block, the Connect block should not be assigned to ListPicker.selection! Also, your Block assumes a lightning-fast connection, which will be true in most cases but you can't bank on it, so testing for "IsConnected" in a Timer Block gets that one out of jail.

[Chris Ward]

Yes, the device that hosts the Bluetooth module - Arduino Uno R3 is a popular choice for example.

See the Links on my website about microcontrollers and Bluetooth - lots of valuable information, set-up examples by various experts and gotchas to avoid.

https://www.professorcad.co.uk/appinventortips#TipsMicrocontroller

https://www.professorcad.co.uk/appinventortips#TipsBluetooth

[Chris Ward]

Shorter time interval = checking more often. Don't over do it.

Note that you will use two timers, one to ensure the initial connection is successful, the other to check that the connection has not broken (typically caused by the Phone moving too far away from the target device - Bluetooth range is limited)

I scrambled the example code together for you as it's getting late here (UK time). It's good practice to give all components meaningful names rather than just Button1, Clock1 etc.

See:

https://www.professorcad.co.uk/appinventortips#TipsGui

https://www.professorcad.co.uk/appinventortips#TipsGeneral

[1446406]

What is Clock_TimerConnect?

[1446406]

nevermind I understand

[Chris Ward]

:)

[1446406]

would I need to set globaltimercount back to zero if the bluetooth connects after being disconnected

[Chris Ward]

Hi

That particular Block is checking to see if the first attempt to connect is a success or not. In either case, the timer disables itself. The expectation is that if connection was not successful, the App would be exited by the User (to examine the target device for example). Once the first attempt to connect is a success, the auto-reconnect block could be used if it is thought that the connection could be lost during a session of data exchange - perhaps because the device is close to the distance limit for example.

That's the long story. If you intend to keep the App running and try to connect again (repicking the target device from the list) after tweaking something, then certainly timer count should be returned to zero before hand. You can do that in the same part of the timer block that reports the error.

[1446406]

Hello again, the app is about finished and am trying to add background music, but the file size is too large. Is there a way to get around this?

[TimAI2]

Reduce the file size, or call the file in on first run of the app from a web resource.

[1446406]

How do I do the second option?

[1446406]

How do I make the app download the mp3 file once it is already on the phone? I want to do this in order to bypass the 10 mb limit on audio and video files.