Audio distorted when BLE is connected

[Epasta]

Hello, we have an android/iOS app on a phone that is connected to my button (nRF51) and to a Bluetooth headset. The app is a kind of walkie talkie that transmit mono audio every time you press the button. What is happen is that if the button is not connected the audio is ok, if the button is connected most of the time the audio is distorted!!! As soon as you turn off the button connection the audio is good again. We did many test and if you don't use the Bluetooth headset but the audio came out directly from the phone , there is no problem. Only if you have both headset and button connected you have the problem!!! There is something I can do? It is really the BLE button connection to use the Bluetooth bandwidth and make the audio distorted? Can I optimize something on my button?

thx

Enrico

[Epasta]

Hi, the parameters are corrects, because i have seen them on bluetooth guidelines of iOs...

"If Bluetooth Low Energy HID is one of the connected services of an accessory, connection interval down to 11.25 ms may be accepted by the Apple product" .(developer.apple.com/.../BluetoothDesignGuidelines.pdf) page 22.. And I am able to connect with all iOs devices...

This button can (raise and decrease volume);

when i push the button I send notification at mine custom service and characteristic (0x01); when i release the button i send notification at mine custom service and characteristic (0x02).

Is not a problem of distance, because the 3 devices are less then one meter distance.

The problem has not a logic, is randomly.

Sometimes when i open audio the "audio" is perfect, sometimes is very distorced.

What connection interval do you suggest to use?

What type of headset are you using? What type of phone, software and application are you using?

Thanks for the time and the help Regands Enrico

[run_ar]

iOS usually wouldn't accept a connection parameter request where min = 7.5 and max = 15, I would expect that these requests are rejected (you would still be connected, but running on slower conn events). Regardless you don't need this fast interval for a button implementation. I would suggest trying something closer to 100 ms to see if the distortion is still there. I don't think the user would notice that delay for a button press. The faster interval is mostly needed if you send multiple button presses e.g. typing.

[Epasta]

what does mean closer to 100ms?! Thanks regards

[run_ar]

Try to ask for min 50 ms and max 100 ms. This would probably give you a connection interval just below 100 ms. Then check if your peripheral behaves satisfactory with this setting.

[Epasta]

if i put min 50 and max 100 the (nrf51dk does not work) the max is that:

MIN_CONN_INTERVAL MSEC_TO_UNITS = 30, MAX_CONN_INTERVAL MSEC_TO_UNITS= 60,

I can't put 50 and 100 you know why? Thanks Enrico!

With this settings the audio has improved

[Epasta]

no sorry, it works as before! no one change