Sending multiple notify packets per connection interval

[Neil_CPD]

Hi,

Device: NRF53

I'm trying to send 3 notify packets in a 15ms connection internal but I can send 2.

I'm using Nrf connect and Zephyr.  is there a limit or a define to set this.

Thank you for any guidance and help

Regards

[Neil_CPD]

Thanks for the update Simon.

[Simon]

I tried to increase the buffers in both the ble host as well as the controller, but it didn't help. I've asked internally about this and waiting for an answer.

[Hung Bui]

Hi Neil, 
 I suspect that the central was not able to handle more than 2 packets per connection event. A sniffer trace would be very helpful to reveal this. 

[Neil_CPD]

Hi,

I will try to get you a sniifer trace but I do remember the more data flag being set to false on the second packet.

I also thought that Simon had tried this test with two nrf dk's.  Could you do a sniifer trace of it working with an nrf dk central please. If it's a limitation of the central then I can explain this to my customer.

Thanks

[Hung Bui]

There is a chance that it's hitting the limit of the stack. But we do need a sniffer trace to really understand the situation. 
Please also look at the throughput example. As far as I know you can reach around 700kbps at 1Mbps.given that the ATT_MTU is configured correctly and Data length extension is applied.

[Neil_CPD]

I've created the same issue that i've been having with a basic hr example using NCS 1.6.1.  in the 1st example I loop round 3 packets then sleep 5ms the other I sleep 30ms. See attached 2 sniffer traces. You can see in the 4ms trace it sends two packets per connection interval to one with 30ms sleep it sends 3 per con interval.hr_example_3packetLoop30ms_sleep.pcapnghr_example_3packetLoop5ms_sleep.pcapng

[Hung Bui]

Hi Neil, 

Attached you can find my example of sending 25 notifications in a 15ms interval connection. 

It's not the maximum limit I believe. If you increase CONFIG_BT_CONN_TX_MAX you should have more but the CONFIG_BT_CTLR_RX_BUFFERS is limited to 18. 
I found that what slowing down the rate in the original centralhr example was the printk inside notify_func() that causing the central to NACK the packet from the peripheral. 

In my test with my Galaxy S10 it achieved similar number of packets.

Please try the example I provided here and if it works please follow the configuration in my projects.

3264.hr_mp.zip

4745.sniffertrace2.pcapng

[Neil_CPD]

Hi,

Sorry for the delay but I been on vacation..

I've spent some time this week trying to re-create the performance that you've managed to find but i've not been able to. I tried with the central and also on my phone but no success. 

I've attached your projects with my build folders in.  If you could please verify on a nrf5340-dk that would be great.

I've also looked at the log for the rpmsg and the messages seem to also be groups of two.3264.hr_mp_NC.zip

nc_hr_mp_test.pcapng

[ovrebekk]

Hi 

Hung is on leave, and I will help you out in the mean time. 

Normally issues with throughput on the nRF53 are caused by not configuring the hci_rpmsg application running on the network core properly. 

If you take a look at the throughput example in the nrf repository you can see that they define a separate config file for this application, in a folder called child_image:
https://github.com/nrfconnect/sdk-nrf/tree/master/samples/bluetooth/throughput/child_image

Can you try something similar for your project and see if it improves the number of notifications you can achieve?

Best regards
Torbjørn

[Neil_CPD]

Thanks for the reply,  I've checked  the "nrf connect SDK project.." in hci_rpmsg_menuconfig and they seem to be correct,  If there a good way to verify that the values have been built into the project?

if I add the child image folder do I need to regenerate the project in nrf Connect?

Thanks

Neil

[ovrebekk]

Hi Neil

Neil_CPD said:

If there a good way to verify that the values have been built into the project?

If you open your build folder, and navigate to the subfolder \hci_rpmsg\zephyr, there should be a file called .config which contains all the pre-compiled configuration settings:

In this file you can search for the config parameter you are interested in (such as CONFIG_BT_CTLR_RX_BUFFERS), and verify that it is set as you expect. 

Neil_CPD said:

if I add the child image folder do I need to regenerate the project in nrf Connect?

Yes. This is not picked up by the build automatically, and you need to re-run cmake in order for these settings to be included. 

You can do this from the command line by running west build with the -c parameter:

west build -c

If you use Segger Embedded Studio there is a menu option to rerun cmake:

Menu -> Project -> Run CMake...

Best regards
Torbjørn

[Neil_CPD]

Hi Torbjørn,

Thank you for the advice.  I can see all the config values that Hung has set in the project that he has attached but this hasn't made any difference I still only get 2 notify packets per connection.

Do you have a nrf5340-dk that you could test with and attach the build folder so I could program the hex as a test please?

Or if you have any other suggestions to try next that would be great.

Thank you.

Neil