l2cap implementation with static uuid and randm channel in nrf5340

RE: l2cap implementation with static uuid and randm channel in nrf5340

Hung Bui — Fri, 10 Nov 2023 10:30:15 GMT

Hi,
Can you step into the code and check why it didn't return.
Could you explain why you want to do credit based L2CAP ?
What's the limitation of the ots that you decide to make the change ?
Have you enabled CONFIG_BT_L2CAP_ECRED=y ?
Have you studied the sample in \zephyr\tests\bsim\bluetooth\host\l2cap ?
I saw that they use bt_l2cap_ecred_chan_connect in credits_seg_recv and credits

RE: l2cap implementation with static uuid and randm channel in nrf5340

manikandan — Fri, 10 Nov 2023 04:09:21 GMT

i too want to close this as soon as possible OTS default sample working fine..my l2cap gets stuck at bt_l2cap_ecred_chan_connect getting unknown error in central

regards

manikandan v

RE: l2cap implementation with static uuid and randm channel in nrf5340

Hung Bui — Thu, 09 Nov 2023 13:18:12 GMT

Hi,
I'm sorry that the issue has been dragging for so long.
But can you clarify that even if you use BT_GATT_OTS_L2CAP_PSM 0x0025 like in ots_l2cap you still can't make it work ?
I don't see why it worked for the OTS but not for you ?
At which step the OTS works , but not your own l2cap channel ?

RE: l2cap implementation with static uuid and randm channel in nrf5340

manikandan — Thu, 09 Nov 2023 03:48:50 GMT

hello thanks for your reply that is also not working my steps

1)initaiting a discovery service with static uuid ABDD3056 28FA 441D A470 55A75A52553A

2)after making ble connection initaiting a l2cap register using this register_l2cap_server

3)and making l2cap connection using bt_l2cap_ecred_chan_connect

4)and sending the data using this bt_l2cap_chan_send

but i still could not be able to mkq the l2cap connection

regards

manikandan V

RE: l2cap implementation with static uuid and randm channel in nrf5340

Hung Bui — Wed, 01 Nov 2023 10:11:05 GMT

Hi Manikandan,
Could you show how exactly you assign the value ?
I think I have confused between PSM and SPSM. It more likely that what we use as psm in our code is actually SPSM.
You can find this :

It's matched with the SPSM in the spec:

So please try using psm value = 0x80, or better set it to 0 and let it dynamically assigned.

RE: l2cap implementation with static uuid and randm channel in nrf5340

manikandan — Wed, 01 Nov 2023 01:52:52 GMT

yes, i have tested with custom psm that is working fine.. but if i give value in the range of >0x1000 i am getting unknown error while making l2cap channel connection with bt_l2cap_chan_connect .. that is where i am stuck

RE: l2cap implementation with static uuid and randm channel in nrf5340

Hung Bui — Thu, 26 Oct 2023 12:00:31 GMT

Hi,
Have you tried use test with fixed custom PSM ?
Have you managed to establish a L2CAP connection with that.
I would suggest to make sure everything is working before you test with dynamic random PSM.

I found this in the spec:

My understanding is that you can choose the PSM value from the initiator side.
Try something like 0x1001.

RE: l2cap implementation with static uuid and randm channel in nrf5340

manikandan — Wed, 25 Oct 2023 11:36:36 GMT

Hello,

I can able to do connection with custom PSM as I have asked in my question I want to make l2cap connection with random PSM (PSM value should genrate after discovery) not custom one

RE: l2cap implementation with static uuid and randm channel in nrf5340

Hung Bui — Wed, 25 Oct 2023 09:36:54 GMT

I'm not so sure why BT_GATT_OTS_L2CAP_PSM has anything to do with service discovery and sending request.
The reason BT_GATT_OTS_L2CAP_PSM has the value 0x0025 because it's a standard PSM service in the spec and it has the value 0x0025:
https://btprodspecificationrefs.blob.core.windows.net/assigned-numbers/Assigned%20Number%20Types/Assigned_Numbers.pdf

If you are doing custom PSM you can choose anything above 0x80.

RE: l2cap implementation with static uuid and randm channel in nrf5340

manikandan — Tue, 24 Oct 2023 15:50:49 GMT

Yes I have seen that but what I am not getting is why they are specifing PSM value as

#define BT_GATT_OTS_L2CAP_PSM 0x0025 in ots_l2cap.c

RE: l2cap implementation with static uuid and randm channel in nrf5340

Hung Bui — Tue, 24 Oct 2023 13:05:29 GMT

Hi Manikandan,
Have you looked at the central_otc sample ?
In the sample, the central does service discovery (discover_func() called in connected() ) then subscribe to notification (subscribe_func () ) and then write to the ots service in otc_btn_work_fn) function.

If you are not familiar with BLE I would suggest to get started with our sample in the SDK and our Bluetooth Academy.

RE: l2cap implementation with static uuid and randm channel in nrf5340

manikandan — Tue, 24 Oct 2023 03:22:48 GMT

yes, i have refered this examples now i can be able use l2cap but only thing i am missing is how to perfrom gatt service discovery from central after establishing a connection want to know how to make central to send a request to peripheral device to set up anl2cap channel using the specfic gatt characteristic or how can i set any custom gatt characteristic?

RE: l2cap implementation with static uuid and randm channel in nrf5340

Hung Bui — Mon, 09 Oct 2023 14:59:40 GMT

Hi Manikandan,

I'm afraid that we don't have further material compare to what I have discussed with your in the last ticket.

l2cap implementation on nrf5340

You need to dig into central_otc and peripheral_ots samples.