CC2640R2F: How to disable initial LL_LENGTH_REQ

Deniz Can Cigsar

Part Number: CC2640R2F
Other Parts Discussed in Thread: CC2640,

CC2640R2F has problem with Realtek adapters in Windows.. It looks like both ends does not comply with standard.. At the beginning of connection, both sides transmit LL_LENGTH_REQ. The specification says LL_LENGTH_REQ can be issued at anytime, also if master sends LL_LENGTH_REQ, the slave should not request but just respond. Instead of responding to LL_LENGTH_REQ coming from master, CC2640 requests LL_LENGTH_REQ as well.. When that happens, Realtek driver transmits procedure error. From specification, I understand that Realtek should not do that, accept the request gracefully..

We set maximum packet length to 27 with HCI_EXT_SetMaxDataLenCmd(27, 328, 27, 328) at the initialization to prevent initial LL_LENGTH_REQ at the beginning of the connection. With this Realtek adapter works flowlessly.. However, that disables DLE completely.. We couldn't figure setting rxLength to 27 other than that..

What could you suggest? We want CC2640 start with 27 bytes rx, 27 bytes tx PDU. Than increase that to 251 etc.. Disabling LL_LENGTH_REQ issued by CC2640, but responding master's LL_LENGTH_REQ with high values would be much better..

over 4 years ago

0 Jan over 4 years ago

TI__Mastermind 44240 points

Hi,

Thank you for reaching out. I have assigned an expert to help you with your query. in the meantime, I have a few questions that will help us resolve this as efficiently as possible. What SDK version are you using? Do you have a sniffer log you can share that details this behavior? If so, then can you share it with us? Is this behavior observable with a non-modified example project?

I have found a few threads that may be helpful. Can you look through them and let us know if they help?

https://e2e.ti.com/support/wireless-connectivity/bluetooth-group/bluetooth/f/bluetooth-forum/1002323/cc2640r2f-ble-connections-failing-due-to-extended-packet-sizes

https://e2e.ti.com/support/wireless-connectivity/bluetooth-group/bluetooth/f/bluetooth-forum/851754/cc2640r2f-dle-activation

https://e2e.ti.com/support/wireless-connectivity/bluetooth-group/bluetooth/f/bluetooth-forum/590090/cc2640r2f-cc2640r2-ble-stack-connection-issue

Best Regards,

Jan

0 Deniz Can Cigsar over 4 years ago in reply to Jan

Intellectual 720 points

Hi Jan,

The SDK version is 4.30.0.8.. simple peripheral app also fails. It's expected though, if you look at the log.. Because it always starts like that..

The sniffer log is the following:

Realtek issues LL_VERSION_IND, meanwhile, before answering the request, CC2640 issues LL_LENGTH_REQ which causes "different transaction collision (0x2A).. The connection is not terminated, but service discovery etc is not executed..

Other adapters do not respond like this. They gracefully send response, which is expected..

If we disable LL_LENGTH_REQ CC2640 sends at the start with HCI_EXT_SetMaxDataLenCmd(27, 328, 27, 328) the connection established successfully, however, this time we loose DLE entirely, which slows down the transfers..

We need to disable CC2640's self started LL_LENGTH_REQ without loosing DLE..

By the way, every master sends this request. We've never seen one that did not.. Why do TI bother sending that? If it were configurable I could understant.. Such as "auto length request" flag etc..

0 Ammar N over 4 years ago in reply to Deniz Can Cigsar

TI__Mastermind 25810 points

Hey Deniz,

Thanks for the logs and the comments. Are you using BLE4.2?

Can you perform this test using the latest SDK and see if you can reproduce the issue?

Another thing you can try is to disable the initial connection parameter update in the application. You can remove the define USE_LL_CONN_PARAM_UPDATE to do this. This will give us some insight on the issue if you are still able to reproduce it with the connection parameter update removed.

Bluetooth®︎

Bluetooth forum

CC2640R2F: How to disable initial LL_LENGTH_REQ