How to configure nRF82540 for using multiple BLE packages in one connection interval?

[Piotr Romaniuk]

Hi,

I try to achieve high throughput via BLE connection between two nRF82540dk boards. I would like to maximize duty cycle of transmission in the connection interval.
Unfortunately I observe only one or two BLE packets in each interval.
How can I configure SoftDevice to transmit more packets in one interval?

I use slighly modified ble_app_uart_c_pca10056_s140 and ble_app_uart_pca10056_s140 as starting point examples for the serial connection.
A stream of 244 bytes packets is sent from peripheral to the central device. 

Other options:
1) BLE PHY 2Mbps,
2) Connection interval = 7.5ms
3) NRF_SDH_BLE_GAP_EVENT_LENGTH = 6

Kind regards,

Piotr Romaniuk

[Karl Ylvisaker]

Hello,

I try to achieve high throughput via BLE connection between two nRF82540dk boards.

Have you seen the throughput test results in the SoftDevice documentation? It details which parameters was used during the tests, to reach the different throughput speeds.

I would like to maximize duty cycle of transmission in the connection interval.

3) NRF_SDH_BLE_GAP_EVENT_LENGTH = 6

Please change your event length to allow for more notifications being sent every connection event.
Since you are only holding a single connection, you can use the entire 'duty-cycle' of the connection interval for this connection.
You thus may set your event length to 500 (or any other high number), to allow for the event to span the entire interval, if needed.
Could you also confirm for me that connection event length extension is configured in your project?
It is default in all newer SDK versions, but I do not know which version you are working with. You might find this answer by my colleague helpful, for an explanation of the parameter.
You may also find the online power-profiler useful to have a look at, to visualize how the different connection settings will affect your radio usage.

Please try this, and let me know if you achieve the sought-after radio usage.

Best regards,
Karl

[Piotr Romaniuk]

Hi Karl,

Yes, I saw the documentation, it reports 1.4Mbps, I have only 250kbps. 

Karl Ylvisaker said:

Please change your event length to allow for more notifications being sent every connection event.
Since you are only holding a single connection, you can use the entire 'duty-cycle' of the connection interval for this connection

In my configuration Connection Interval is set 7.5ms, and NRF_SDH_BLE_GAP_EVENT_LENGTH = 6 (i.e. 6x1.25ms = 7.5ms) hence I assigned whole interval for communication. The chip should transmit with almost 100% duty cycle, but it doesn't.

As you saw on the oscillogram above setting of the event length is not effective. The SoftDevice transmits mostly one packet in the cycle.

What I am doing wrong?

Kind regards,
Piotr Romaniuk

PS
I am using SDK 17.0.2 (nRF5_SDK_17.0.2_d674dde)

[Karl Ylvisaker]

Hello Piotr,

Piotr Romaniuk said:

Please scroll up to the first message!

You only ever mention which SDK version and SoftDevice you are working with - SDK v17.0.2 and S140. SoC variant and SoftDevice version is still not known to me. I know that you are working with the S140 - but which version of the S140 are you working with? Which nRF52840 revision is it??
I assume it is either nRF52840 revision 1 or 2, but I would like to be certain. You can find the build code on the nRF52840 chip.

Please let me know which S140 version and nRF52840 SoC version you are working with, so I may rule out compatibility being the issue here.

Best regards,
Karl

[Piotr Romaniuk]

Hi Karl,

board 1:

  label on 1st chip:
      PCA10056
      2.0.1
      2020.43
      followed by the serrial number.

 nordic chip:
     N52840
     QIAAD0
     2007FV 

     

and board 2:
     PCA10056
     2.0.1
     2020.37

nordic chip
    N52840
    QIAAD0
    2020J8

Are the numbers that you asked for?

According to Softdevice version I only know that I use S140 from SDK 17.0.2. I don't know how to check more. Maybe I missunderstood version numbering [?]

I thought that Softdevice is programmed together with my program as precompiled binary module. Is it true?
I assumed that by selecting folder pca10056 and its subfolder S140 for Segger Embedded Studio project I have selected what chip version and Softdevice version I use. I also assumed that S140 will support all the chips.
I am I wrong?

Kind regards,

Piotr Romaniuk

[Karl Ylvisaker]

Hello Piotr,

Piotr Romaniuk said:

Are the numbers that you asked for?

Yes, the numbers on the Nordic chip - QIAAD0 - is the build number, and tells us that these are Revision 2 chips, great!

Piotr Romaniuk said:

According to Softdevice version I only know that I use S140 from SDK 17.0.2. I don't know how to check more. Maybe I missunderstood version numbering [?]

Thank you for clarifying.
The SoftDevice is located at nRF5_SDK_17.0.2_d674dde\components\softdevice\s140\hex in the SDK, and the name will contain its version. If you have not made any changes to this, SDK 17.0.2 ships with S140 v7.2.0 by default.

Piotr Romaniuk said:

I thought that Softdevice is programmed together with my program as precompiled binary module. Is it true?

This is correct, the SoftDevice is supplied as a precompiled hex file, which is programmed together with the application when the preprocessor defines S140 and SoftDevice_present is set. 

Piotr Romaniuk said:

I assumed that by selecting folder pca10056 and its subfolder S140 for Segger Embedded Studio project I have selected what chip version and Softdevice version I use. I also assumed that S140 will support all the chips.
I am I wrong?

No, you are not wrong - the SDK only contains compatible SoftDevice versions.
The reason why I asked for SoftDevice version is because customers sometimes use older versions of them without ensuring that the SoftDevice version they are using is compatible with the SDK version they are using. This could have been the reason for the RAM adjustment warnings you are getting. It sounds to me like this is not the case here, however. My apologies if this seemed like a unnecessary detour from the issue, I just wanted to rule out compatibility issues being the cause.

Did you try to do the RAM adjustments as detailed in the warning, by the way? Did this resolve the NRF_ERROR_NO_MEM error you were getting?

Best regards,
Karl

[Piotr Romaniuk]

Hi Karl,

I did not try yet RAM adjustment.
Can you send me exact expression that I should write into linker window options?
I browsed source code including linker script and I am really confused.

I very concerned that the same problem (i.e. with memory) exists in Nordic original example (ble_uart project) without any modification. I plan to open new case for that, because it is basic code and is not influenced by any my changes.

I am very worried that I stuck in some basic issue, that further coding depends on. We are sending one message per day.
I am sending you private messages in chat window. I am not sure if you receive them?
Maybe chat will be faster to determine the cause of the problem.

Kind regards,
Piotr Romaniuk

[Karl Ylvisaker]

Hello Piotr,

Piotr Romaniuk said:

I did not try yet RAM adjustment.
Can you send me exact expression that I should write into linker window options?
I browsed source code including linker script and I am really confused.

I have attached an image that shows how it should look for you, after you have made the RAM start changes. The exact expression is the same as written in the warning in your log, and the location can be found by right clicking on the 'Project' in SES project explorer, selecting 'options', selecting 'Common' configuration, opening the 'Linker' tab, and double clicking on the 'Section Placement Macros'. Make sure to click OK to close all windows, once you have made the changes.
Please do this, and let me know if it resolves your error. 

Piotr Romaniuk said:

I very concerned that the same problem (i.e. with memory) exists in Nordic original example (ble_uart project) without any modification. I plan to open new case for that, because it is basic code and is not influenced by any my changes.

I have tested this on a mint SDK, and I am not seeing this issue.
Are you certain that you have tested this on an example which you have made no changes to?
The SoftDevice's memory footprint may change if you change its configuration, and this may be the reason why you have to update the RAM_START macro.
Could you download a mint version of the SDK 17.0.2, and see if you get this error there as well? If the issue persists, you should open a new ticket for this, yes.

Piotr Romaniuk said:

I am very worried that I stuck in some basic issue, that further coding depends on. We are sending one message per day.

This is indeed a seemingly basic issue, but I hope and think this error will be resolved when you change the RAM_START macro.

Piotr Romaniuk said:

I am sending you private messages in chat window. I am not sure if you receive them?
Maybe chat will be faster to determine the cause of the problem.

It is best to keep all related information in the ticket, so it may be of use to other's experiencing the same, or a similar issue, later, and to easily look up earlier information regarding the issue. The chat feature is not quicker than the tickets, unfortunately.

I look forward to hearing the effects of the RAM_START macro change, on your issue.

Best regards,
Karl