Problem in data transfer in Bluetooth at 10ms

[sharmelaraju]

Hi,

We are using NRF52840 Dk board to transfer the data at 10ms through Bluetooth which is central and peripheral  as other cc250moda controller  Bluetooth. Our objective is to send the data of 8 bytes at  10ms from the NRF52840 Bluetooth to other Bluetooth. We are able to send the data from NRF52840 Bluetooth of 8 bytes at 30ms,50ms,100ms,500 ms to other controller Bluetooth correctly which means at every 50ms  we are sending 8  of bytes data which is receiving  8 bytes of data at every 50ms in the receiving controller Bluetooth. The problem here is when we are sending the  8 bytes of data at 10ms from NRF52840  Bluetooth to  receiving Bluetooth it should read  8 bytes of data at 10ms but here the problem is it is reading as 8 bytes, 16 bytes ,24 bytes ,0 bytes ,0 bytes, 24 bytes,16 bytes, 0 bytes, 0 bytes  as such at every 10 ms.Can you please tell me what is the problem . How to resolve the issue.

[sharmelaraju]

Sorry for the delayed response.

Still i am getting the same thing while logging the data in the ble sniffer.

I have even tried nrf52840 as (peripheral) and cc2564 moda Bluetooth as central.Still i am not able receive  the data at every 10ms .

please help me with the soluion.

[Karl Ylvisaker]

sharmelaraju said:

Sorry for the delayed response.

 No problem at all.

sharmelaraju said:

Still i am getting the same thing while logging the data in the ble sniffer.

Did you take a look at the sniffer trace I attached in my last reply?
Are you unable to see the master-slave communication happening as shown in the trace? 
If so, could you verify that the two modules manage to connect to each other? If you are not seeing the master-slave communication, and not receiving the data, then it is possible that the two devices are not connecting to each other.

The master-slave communication should show up in the sniffer as soon as the connection is established.

Could you verify if this is the case, and get back to me?

Best regards,
Karl

[sharmelaraju]

Hi,

Thanks for the reply.

I am  here by attaching the captured sniff data between the central and peripheral.captured_logdata.pcapngcaptured_log1data.pcapng

[sharmelaraju]

Plz give me the solution.

[Karl Ylvisaker]

Hello again,

Those logs were much better, thank you.

When viewing the logs, this seems exactly as it should be to me.
The delta time for each transmission is ~10 ms for each transmission. From this, we can now be sure that you are in fact completing your data transmission (the 0x11, 0x12, 0x15 .. data) every 10 ms.
If you take a look at packet number 531 particularly, that is when the central initiates the connection - with 8 as connection interval, which translates to 10 ms (8 * 1.25 ms).

Seeing this, in combination with the printed UART log you shared earlier(where the data is not being processed right away after being received. So, that leads us to examining what the peripheral spends its time doing.

When does the data handling happen? Could it be that your device is over encumbered, and thus not always finish its processing of the received data in time, before a new packet is received?
It could also be that the UART logging itself is what pushes the peripheral to miss its processing windows - are you using deferred logging?

Best regards,
Karl