Error 507: Unable to connect

I’m new at this feature and unluckily I’m facing with problem right on the beggining.

I need to connect my phone to another BT device. Because I don’t have that device yet (HC-05 for Arduino), I’m trying to connect to another phone, BT speaker or BT mouse.

The problem is that after choosing a paired device from list picker, the error message appear. I’ve already tried to connect it as:

  1. paired but not yet connected device,
  2. paired & already connected device.

In both cases error message “Error 507: Unable to connect. Is the device turned on”? appeared despite the fact that device is turned on or, in addition already connected. Without the connection I can’t move forward with programming my app.

Thanks for help in advance!!

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Error message on phone.

Firstly I tried it only via Honor View 20. This time I used Xiomi Redmi Note 4 and exactly same error message appeared. I have no idea, where could be the problem :confused:

I’ve searched on internet a lot and found on a lots of forums, that MIT App Inventor hardly ever supports other BT devices than Arduino modules.
So I hope, it will work in my case.

Hi @HappyJuice

The BluetoothClient component only supports devices that support the Serial Port Profile (SPP). If your device supports RFCOMM over a UUID other than the SPP UUID, you’ll need to use the ConnectWithUUID block and specify the UUID required by your device.


HI even i am facing the same issue . My bluetooth devices are turned on but still i am getting error : 507 unable to connect is the device turned on. Le me know the solution

I even tried with the automatic connection with out the listpicker option .let me know how can i get conneted

Hi, I Too have the same problem but i am using mBot with a robot arm built in using pca9685
more information about mbot can be found here

Please Help,

++So how do you find the UUID of a device?

Hi all,

any progress on the "507" error?

I also want to connect an MITinventor project to a HC-05 Bluetooth module.

Any of the suggested projects does not work. It will come up with the " ERROR 507. Unable to connect"

There is only one app, Arduino Bluetooth Controller ( HM-10 Module), that does connect to the HC-05. But unfortunately I can not alter the app to my usage.

What is the general problem with " Error 507" ?



The method takes two arguments. The first is the MAC address of the Bluetooth device. The second is the UUID of the service it advertises. The Connect method will always use the UUID of the SPP service. If you want to use a different service, presumably the manufacturer will tell you what the UUID is. Alternatively, you might be able to use another app to query for all of the UUIDs published by a Bluetooth device to get the UUID you need.

? So what would this look like?
How would you find this info?

Hello Eric

Can you please give us some detailed information:

  1. The Manufacturer and Model of your Android Device (e.g. Phone, Tablet)
  2. The Name of the Device you are connecting to (e.g. Ardunio Uno with HC-05 Bluetooth Module)
  3. Your App comms. e.g. Send and Receive, Send only, Receive only.
  4. What does your App Do? e.g. controls a robot, collects sensor data etc.
  5. How far have you got with your project?

My Connection issues:
Attempting to send text such as (S1F, S4B, S16N,....)
Using Android phone (Samsung Galaxy S9+) to:

*original attempt was Raspberry Pi4 with Waveshare servo control HAT (the Pi has onboard Bluetooth)
the text decoded on the device: S1F would rotate servo number 1 fully clockwise. S4B turn servo number 4 fully counter clockwise S16N turn servo number 16 to the mid position for these 180 degree rotating servos.

Raspberry, Waveshare, and Youtube led me to believe this would be a simple task for someone new to their devices. Totally NOT true. Maybe if you had someone tutoring you, then possible because they could lead you into success.

I gave up on the Raspberry Pi and got an Arduino Uno Wi/Fi Rev2 (because it also has the on board Bluetooth and I would not need to buy or connect additional components)

I copied everything from Binary updates Youtube video. But no joy.. (I figure there must be some special commands/coding that I need to enter because of the on board Wi/Fi capabilities. But I don't know where to start with that)

So I decided to get a HC-05 Bluetooth module. Making another attempt at copying everything exactly the same as the Binary Update Youtube video. This time, the HC-05 module could be seen on my phone. I was able to pair it with the phone. But... it would give me error messages in the MIT app and not turn the led on or off.

And this is where I am at today. I am waiting for Fedex to deliver an ELEGOO UNO R3. No bells, no whistles, just base UNO.

In all this, MIT app inventor is the only thing that seems simple.

All I want (and this seems to be what many others want as well) is the ability to control a servo shield with 16 servos using the MIT app. Like most people, I don't really want to learn in depth coding. Just enough to make simple changes to sample code.

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You have a lot of study material here. If you build some blocks and there are still problems. Place your blocks here along with a description of the problem.

This Topic may help you, it has App Inventor code and an Ardunio Sketch. It drives a very simple Robot Arm:

I would like to know how to connect a raspberry pi 3B in bluetooth to an App Mit inventor application or I have created an application. I would like to know how to connect a raspberry pi 3B to a bluetooth app mit inventor or I have created an app mit inventor. This app scans the devices around and must connect to the selected device, in this case the raspberry pi 3 B but for a test phase I try to connect it to a smartphone.

Hello Cristian

The first thing you need to find out is the exact Bluetooth version of the devices involved.

On the raspberry Pi 3B we have a version of 5.50 and on the smatphone we have version 10. I don't know the world of bluetooth so if you could please explain, thank you.

There isn't a version 10 Bluetooth Cristian - that is probably your Android OS version.

The BT versions are important because:

  1. Devices must be compatible with each other
  2. There are two types of Bluetooth

Some reading: