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LAUNCHXL-CC2640R2: Increasing MTU size starts causing errors

Sarthak Tanwani
Intellectual 340 points

Part Number: LAUNCHXL-CC2640R2

Hi,

I am developing a custom application based on project zero. Currently, I am using the blestack and not the ble5stack. In my application, the device is supposed to prepare data at a set interval and send it via notifications to the phone at a set interval (set by the user of a phone application). The data I need to send has a maximum length of around 200 bytes. Therefore, I need to increase the MTU size from the default to 251. I am using the nRF connect app for this. But as soon as I increase the MTU size and try to send or receive data from the device, it starts showing error on the nRF app log and usually disconnects due to timeout. Here I have attached images of the log and GATT error codes it shows.

Also, there was no error shown in the Device UART log. It just shows "connection timed out" and then starts advertising again.

As you can see, I set the MTU size to 251 at log #000043. It tries to send data to a notification after that but the connection times out. Similar to what happens after log #000094.

I need to send data that is larger than the default MTU size.

What could be causing the problem and how should I solve it?

I am using Simplelink SDK version 4.20 and TI compiler version v16.9.1.LTS .

  • 0
    TI__Mastermind 25810 points

    Hey Sarthak,

    I've assigned your post to an expert to comment. In the meantime, I have some clarifying questions that I hope will provide some more context.

    As you are using project zero, what characteristic are you using to send notifications from? Is that characteristic configured for notifications? If you have made any modifications in this regard, please share them. To further clarify, does this issue occur only when sending larger amounts of data (around 200 bytes)? Have you tested this with notifications of smaller sizes, one that will not require a change in the MTU size?

    The logs indicate the phone terminated the connection for some reason. Have you tried using our BTOOL application running the host_test firmware as your central instead?

    It would be good to provide some of the code changes made. If you can narrow it down to only the modifications that are necessary to reproduce this issue, this would help.

    Last note, you may want to update to the latest SDK. At this point I don't have enough information to say this will fix this issue, but this will be a good sanity check if perhaps the issue you encounter was fixed in a later SDK.

  • 0
    TI__Guru** 101540 points

    Hi,

    Based on this thread, it looks like the issue is solved and was due to some memory issues.

    Thanks and regards,