Polar H10(peripheral) do not immediately disconnect from NRF52(both central and peripheral) after removing from the chest.

[Sami Ul Haq]

Hello Team,

I am using the ble_app_hrs_rscs_relay example where NRF52 acts both as a central and peripheral. My question is that when I remove the heart sensor Polar H10( which is a peripheral) from the chest, it doesn't disconnect from NRF52 immediately after removing it from the chest but it takes a longer time to disconnect. I want that when I remove Polar H10 from the chest and it disconnects Immdeditaly. Any help regarding this will be highly appreciated.

I am using NRF52 and SDK 17.0.2 and soft devices s140.

Kind Regards,

Sami Ul Haq

[Karl Ylvisaker]

Hello Sami Ul Haq,

In order to achieve this you will need a mechanism to sense that the sensor is removed from the body, to trigger the disconnect.
You may then trigger the disconnect as part of the handling of the event for when the sensor is removed from the body.
Please keep in mind that I have no prior experience with the Polar H10 sensor, so I do not know how you can measure this event exactly, you will need to check the sensor's datasheet for this.

Best regards,
Karl

[Sami Ul Haq]

Hello Karl sir, Thank you for coming to help. 

Karl Ylvisaker said:

In order to achieve this you will need a mechanism to sense that the sensor is removed from the body, to trigger the disconnect.

The disconnect Event Is calling upon the removal of Polar H10(peripheral) but not immediately after the removal of Polar H10 but take some time and then got disconnected. Maybe the Heart sensor is still advertising for some time after removal but I am not sure, or maybe it's the NRF52 microcontroller that doesn't call disconnect event immediately after removing the polar H10. 

Kind regards,

Sami

[Karl Ylvisaker]

Hello Sami,

Sami Ul Haq said:

I am not sure, or maybe it's the NRF52 microcontroller that doesn't call disconnect event immediately after removing the polar H10. 

This is probably because the nRF52 is acting as a central, and does not know if the sensor is removed or not.
For example, if the peripheral just stops functioning, it will take the duration of the connection supervision timeout before the central terminates the connection.
You can check whether or not this is the case by using the nRF Sniffer tool, to see if the peripheral properly terminates the connection when it is removed.

Best regards,
Karl

[Sami Ul Haq]

Thank you, sir. 

Karl Ylvisaker said:

You can check whether or not this is the case by using the nRF Sniffer tool, to see if the peripheral properly terminates the connection when it is removed.

Sir can you please suggest to me a tutorial on how to use the nRF Sniffer tool as I have never used it before and don't know about it. 

Regards,

Sami

[Karl Ylvisaker]

Hello again, Sami

Yes, absolutely, no problem :) 
You can download the nRF Sniffer tool from here and read about how to install and use it here.
When you have the sniffer tool up and running you can monitor the on-air BLE transmissions, so that you can see whether or not the peripheral just stops sending (turns off), or whether it tries to terminate the connection.
In case of the former you will have to reduce the connection supervision timeout connection parameter of your connection, but this might cause link instability if packets often are lost between the central and peripheral.

Best regards,
Karl

[Sami Ul Haq]

Thank you Karl Sir,

Karl Ylvisaker said:

You can download the nRF Sniffer tool from here and read about how to install and use it here

I am going through these links and will be back if I didn't understand something. 

Regards,

Sami Ul Haq

[Sami Ul Haq]

Hello, again Karl sir,

Karl Ylvisaker said:

When you have the sniffer tool up and running you can monitor the on-air BLE transmissions, so that you can see whether or not the peripheral just stops sending (turns off)

I have gone through the process of the nRF Snipper tool and I have tested the Polar H10 by capturing its packet in Wireshark and came to the conclusion that the Polar H10 does not stop advertising upon the removal but take some time and then the advertising stopped after some time. What will be the possible solution in this case?

Regards,

Sami

[Karl Ylvisaker]

Hello again, Sami

I am glad to hear that you have familiarized with the sniffer tool and have been able to use it, great!
This is a powerful tool to wield when developing BLE application.

Sami Ul Haq said:

came to the conclusion that the Polar H10 does not stop advertising upon the removal but take some time and then the advertising stopped after some time. What will be the possible solution in this case?

Then this becomes much harder. Do I understand it correctly that you have no way to reprogram the H10 sensor? If so, you will need to figure out an event on the central side to terminate the connection, and this event should only ever happen when the sensor is removed.
Perhaps there is a drop in the data sent when the sensor is removed, could you perhaps apply a filter to this?

Best regards,
Karl