Bluetooth not connecting

RE: Bluetooth not connecting

williammoberg — Tue, 11 Nov 2025 06:44:59 GMT

Hey, I ran into something similar a while back, one of my BLE modules would connect fine on macOS but refused to pair properly on Windows. In my case, it turned out to be a mix of driver and module compatibility issues. Windows tends to cache older Bluetooth profiles, which can cause confusion when the same device name shows up multiple times.

You might want to clear your Bluetooth pairing history from Device Manager and re-pair the module after a restart. Also, make sure the COM port assigned to the BLE module isn’t conflicting with another device — that’s a surprisingly common cause of dropped or incomplete connections.

If you’re using a generic BLE dev board, it might help to test with a simpler serial-based Bluetooth setup first, like an HC-05 Bluetooth Module. It connects over UART and behaves more predictably with both Windows and Mac since it uses standard serial-over-Bluetooth communication. That’ll help confirm whether the issue is in the host side (driver/OS) or with your BLE firmware.

I’d also suggest checking if your module advertises as both BLE and classic Bluetooth simultaneously — some devices broadcast multiple profiles, which causes those duplicate entries you’re seeing on Mac.

RE: Bluetooth not connecting

bscdb — Fri, 25 Jan 2019 17:55:52 GMT

The issue just magically disappeared by connecting to another Windows 10 machine!! Now there are no bluetooth connection problems on any machine!

RE: Bluetooth not connecting

awneil — Fri, 25 Jan 2019 14:18:39 GMT

[quote userid="25682" url="~/f/nordic-q-a/42838/bluetooth-not-connecting/167955"]upload both logs using Insert -> Code[/quote]

This - but, for logs, leave the language as 'Text':

RE: Bluetooth not connecting

Bjørn Kvaale — Fri, 25 Jan 2019 13:54:59 GMT

Yes, I agree with awneil. I would definitely recommend debugging both examples & seeing where the difference occurs. Just upload both logs using Insert -> Code & we can continue taking a look.

RE: Bluetooth not connecting

bscdb — Wed, 23 Jan 2019 18:06:32 GMT

1. I just bought a new Windows 10 laptop.

2. The nrf52832 board which does not give problems is v.0.9.0. The one not connecting to Windows PC is v.1.2.4 (which I recently bought)

3. I tried erasing the chip using JLink & nrfStudio

4. I dont think debugging the code would help coz the v.1.2.4 board connects to nrfConnect so clearly there is no issue with the firmware or flashing different soft device or different hex file.

5. If I change the bluetooth device name, the board will show up with 2 names - the old one & the new one and connects to one of them and keeps toggling between paired & connected states. After I remove and uninstall both device names & restart both PC & board, same behavior repeats.

6. I understand that I should not directly wire up nrf board to Windows PC but that is bound to happen sometime. There should be a fix for that. I'll have to flash the code through USB.

RE: Bluetooth not connecting

awneil — Wed, 23 Jan 2019 15:19:31 GMT

Are both of your boards the Nordic nRF52-DK ?

Are they identical?

Maybe the non-working one has been damaged or mis-configured?

Are you loading the exact same code - including SoftDevice - on both?

Have you tried a full chip erase?

Have you used the debugger to see what's happening in both cases - and see where they differ?

RE: Bluetooth not connecting

Bjørn Kvaale — Wed, 23 Jan 2019 14:45:52 GMT

@bscdb Which version of Windows 10 are you using? If it is an early version of Windows 10, it may not work all too great as Nguyen Hoan Hoang mentioned.

Also, have you tried to turn off Bluetooth for about 10 seconds & then turn it back on. That is how you clear Bluetooth cache on smartphones at least. I am assuming it is the same in Windows.

RE: Bluetooth not connecting

Bjørn Kvaale — Wed, 23 Jan 2019 14:39:18 GMT

Which version number does it say on the line below PCA10040 on the white sticker on the two nRF52 DKs (e.g. v1.2.1)?

RE: Bluetooth not connecting

Nguyen Hoan Hoang — Tue, 22 Jan 2019 20:30:03 GMT

I see HID has a different behaviour. Either Keyboard our Mouse HID, it require a pairing. I have not work with HID. Windows seems to have problems with HID keyboard. I saw the similar behaviour when a friend of mine tried to connect an Apple BLE keyboard to Windows. It took a while to get it connect properly. Also if there are other PC or Host device in the surrounding. It may have a race bonding of multiple host trying to connect to the same HID keyboard. Causing the PC to connect/disconnect constantly.

RE: Bluetooth not connecting

bscdb — Tue, 22 Jan 2019 19:58:52 GMT

I was trying with ble hid examples. I think both boards have same firmware with same bluetooth name and different physical address. Windows is somehow restricting this duplication even if I try changing the name in firmware.

RE: Bluetooth not connecting

Nguyen Hoan Hoang — Tue, 22 Jan 2019 19:54:36 GMT

I am not a Windows user, not sure how to flush the cache. What does that firmware supposed to do ? Have you check for a Windows update. Early Windows 10 does not work well with BLE as I know.

RE: Bluetooth not connecting

bscdb — Tue, 22 Jan 2019 19:51:55 GMT

Thanks Nguyen.

I tried just now. The board which was working is showing duplicate bluetooth device names and does not connect to either.

How do I completely clear bluetooth cache on Windows?

I think both boards have same firmware with same bluetooth name and different physical address. Windows is somehow restricting this duplication even if I try changing the name in firmware.

RE: Bluetooth not connecting

Nguyen Hoan Hoang — Tue, 22 Jan 2019 19:49:57 GMT

It seems that board was paired with a different firmware. If possible, try to delete the device from Windows Bluetooth settings. A reboot of Windows may help as well.

RE: Bluetooth not connecting

bscdb — Tue, 22 Jan 2019 19:33:22 GMT

Yes Nguyen, both are nrf52832 boards.

1. I flashed both boards with same hex files.

2. The one board which is not working seems to automatically connect to Windows' bluetooth and keeps switching from paired & connected statuses.

3. I tried uninstalling the device on Windows but in vain.

4. I tried assigning different bluetooth names as well.

5. I tried erasing bond info in firmware but does not help.

RE: Bluetooth not connecting

Nguyen Hoan Hoang — Tue, 22 Jan 2019 19:27:52 GMT

First thing first, are both boards the same hardware. i.e same board revision ? Did you flash both boards with the same hex ? If not, try that first. To eliminate the hardware issues. After that you can debug the software.

RE: Bluetooth not connecting

Bjørn Kvaale — Tue, 22 Jan 2019 16:14:25 GMT

As awneil suggests, I would try to debug the example. Also, maybe try changing the usb cable or usb port? Maybe you are not getting enough power to the nRF52 DK?

RE: Bluetooth not connecting

awneil — Tue, 22 Jan 2019 15:42:34 GMT

again, have you tried using the debugger in the two cases to see what's different / where it goes wrong ?

RE: Bluetooth not connecting

bscdb — Tue, 22 Jan 2019 15:39:06 GMT

Hi Bjorn, I am using Windows 10. The advertising led on first nrf board glows at irregular intervals. I also tried connecting P21 to Vdd but that did not help. I tried all ble examples. The peripheral examples seem to work. But it connects to nrfConnect surprisingly. Also there is no problem in my Windows machine because the ble examples work on the other nrf board!

RE: Bluetooth not connecting

awneil — Tue, 22 Jan 2019 15:38:57 GMT

thanks for the clarifications

RE: Bluetooth not connecting

Bjørn Kvaale — Tue, 22 Jan 2019 15:37:34 GMT

[quote user="awneil"]How is this any different from mobile phones / tablets?[/quote]

Also, most BLE examples have been tested extensively with nRF Connect for Mobile on multiple smartphones, so the nRF5 examples should work out of the box on most smartphones.

RE: Bluetooth not connecting

Bjørn Kvaale — Tue, 22 Jan 2019 15:25:20 GMT

awneil I'll update my last comment. We have noticed issues with some Windows 8 computers connecting directly to an nR5 52 DK because of the BLE driver used on the Windows 8 side.

Like you mentioned, in Windows 7, there was not standard API for BLE, which is one of the reasons why we decided to use an nRF5 device as a connectivity chip.

My guess is that the Bluetooth drivers on Windows or Android were more updated from the start compared with Windows 7?

However, this should work better on Windows 10, due to updated drivers.

Also, by using the connectivity chip solution, we control both sides of the link, making it easier to debug any potential issues.

Of course, if you want to save on cost or not have a dongle sticking out of the PC, we do have a or some examples that should run directly from the Bluetooth chip on Windows 8/10, such as the HID mouse example. It may also work out of the box on a Mac. I am however not sure if this has been tested extensively.

RE: Bluetooth not connecting

awneil — Tue, 22 Jan 2019 14:00:29 GMT

[quote userid="25682" url="~/f/nordic-q-a/42838/bluetooth-not-connecting/167123"]Are you using Windows 8 or Windows 10?[/quote]

sd - you do realise that Windows 7 does not support BLE (even if the hardware is there) ?

[quote userid="25682" url="~/f/nordic-q-a/42838/bluetooth-not-connecting/167123"]we do not advise connecting from a computer (Windows or Mac) directly to an nRF52 DK device because the Bluetooth chip on your computer may have issues connecting to the nRF5 device[/quote]

Really?

😮

Surely, if the computer has BLE (both HW and SW), it should have no problems?

How is this any different from mobile phones / tablets?

RE: Bluetooth not connecting

Bjørn Kvaale — Tue, 22 Jan 2019 13:53:02 GMT

1) Are you using Windows 8 or Windows 10? Which nRF5 example have you tested with?

2) Are you connecting directly from the Mac or Windows Bluetooth settings to the nRF52 DK? When you change the device name of the nRF52, it may be that you need to clear bluetooth cache (just try turning Bluetooth off for about 10 seconds & then turning Bluetooth on again) on your Mac to see the updated device name.

In general, we do not advise connecting from a computer (Windows or Mac) directly to an nRF52 DK device because the Bluetooth chip on your computer may have issues connecting to the nRF5 device.

Update: Slightly misleading comment above. Thanks for picking it up awneil! You can connect some examples directly to a Windows computer (such as HID mouse), however most examples have not been tested directly with the computer's Bluetooth chip. If they have been tested with nRF Connect for Desktop, an nRF5 device was used as a connectivity chip in most examples.

If possible, we recommend connecting your computer to an nRF52840 dongle for example (or an nRF5 DK) to use as a connectivity device between the computer <-> BLE <-> nRF52 DK. You can then easily test using nRF Connect for Desktop BLE app for example.

Another thing you can test is to connect to the nRF52 DK via your mobile phone nRF Connect for Mobile app just to see that the connection to the DK is succesfull. If this is the case, the issue most likely lies on the Windows/Mac side.

RE: Bluetooth not connecting

awneil — Tue, 22 Jan 2019 10:52:34 GMT

[quote userid="73596" url="~/f/nordic-q-a/42838/bluetooth-not-connecting"]does not seem to connect on Windows machine[/quote]

What "Windows machine" ?

[quote userid="73596" url="~/f/nordic-q-a/42838/bluetooth-not-connecting"]but connects on Mac[/quote]

So have you tried using the debugger in the two cases to see what's different / where it goes wrong ?

[quote userid="73596" url="~/f/nordic-q-a/42838/bluetooth-not-connecting"]When my other nrf device is visible on Mac, it displays duplicate names[/quote]

That is expected behaviour!

The Mac only displays the name which the peripheral provides - so the only way around this is to give your peripherals distinct names.

On Android, you can see the MAC address - but iOS does not allow this.

😞