central cannot connect to a device, always 0x3e

RE: central cannot connect to a device, always 0x3e

Vidar Berg — Mon, 08 May 2023 10:05:30 GMT

Changing this behavior will require a new Softdevice release from us. I will make a feature request for this internally. However, I can't promise that it will be done. I recommend you contact our sales representative for your area if this is a critical feature for your product.

RE: central cannot connect to a device, always 0x3e

daoms — Sat, 06 May 2023 02:40:20 GMT

Thanks for your clarification.

Unfortunately I'm not able to get any support from device side.But even if there is something wrong with device implementation, Nordic should be able to cover that, as Phone does.

I burned 2 different version firmware to the 52832 board ,to play with the same device. You can see the sniff below,the only difference is CSA(other paramteres like interval/offset have no affect after tried).

Appreciate any advices for I don't want to use the old SDK.

NRF5_SDK_17.0.2 NG

NRF5_SDK_13.1.0 OK

RE: central cannot connect to a device, always 0x3e

Pål Håland — Fri, 05 May 2023 09:47:32 GMT

Hi daoms,

Thank you for contacting us regarding this issue.

As far I can see regarding the Bluetooth Specification the Central device is permitted to set the ChSel bit both 0 or 1 if it support CSA#2. If it only support CSA#1 then it shall set it to 0.

It could have been a courtesy to set it to 0 in case a peer device is not handling the use of RFU bits correctly. But per the specification we are not doing anything wrong here, in fact the Peripheral device is.

Could you tell us more about the product that you are having issues with, and also provide the sniffer log for both the failing case, and the working case in case there are something else that you have overlooked? Have you tried to contact the vendor of the peer device to ask their Chip manufacturer to provide a bug-fix for their implementation?

Best regards,
Pål Håland
Nordic Semiconductor ASA

RE: central cannot connect to a device, always 0x3e

daoms — Fri, 05 May 2023 03:01:01 GMT

The advertiser of course will ignore the Chsel field because it doesn't have this field. It always uses CSA1,but the initiator use CSA2 in its CONNECT_REQ packet, they don't speak in the same way, this is why they cannot make connection.

So it seems that the new Nordic softdevice is not compatitable with old BLE4.0, because it always CSA2 to speak to a CSA1 device.,which results to a fail connection.

Am I right?

RE: central cannot connect to a device, always 0x3e

Vidar Berg — Wed, 03 May 2023 06:45:36 GMT

The Bluetooth team said the advertiser should ignore the Chsel field if it is based on Bluetooth version <5:

"In 5.0 this field in the INIT PDU was changed from RFU to ChSel, and the receiving device (when not supporting it, or not knowing what it is version < 5.0 ) should set it to 0 and ignore it."

[quote user="ble_starter"]BTW,could you please tell which old verison has CSA1 ,for I suupose you can get it easier interanlly.[/quote]

Of course. You can use nRF5 SDK 13.1.0 with s132 v.4.0.x (SDKs and SoftDevices). This Softdevice is based on Bluetooth 4.1.

RE: central cannot connect to a device, always 0x3e

daoms — Wed, 03 May 2023 02:23:58 GMT

I cannot ope the device,but I heared that the chip is from realtek.

As you mentioned in previous reply,"The softdevice will fallback to CSA1 ...required by spec",so when does this case happen?Is it that initator analyzes the advertise and gets to know the peripherall use CSA1 ,it then use CSA1 in its CONNECT_REQ?

If so ,it seems that nordic softdevice doesn't obey to bluetooth spec.Becasue it STILL sends a CSA2 CONNECT_REQ even it gets a CSA1 advertise.

BTW,could you please tell which old verison has CSA1 ,for I suupose you can get it easier interanlly.

Thansk

RE: central cannot connect to a device, always 0x3e

Vidar Berg — Fri, 28 Apr 2023 14:35:57 GMT

I see what you mean now - ChSel is '2' in the CONNECT_IND packet even though the advertiser has it set to '1'. Are you able to share any details about the BT chipset you are trying to connect to? I will follow up with our Bluetooth team to hear what they think abou this.

In the meantime, if it is not too much work, you could try to test with an older Softdevice that does not support CSA #2 do see if you get the same problem.

RE: central cannot connect to a device, always 0x3e

daoms — Fri, 28 Apr 2023 13:12:16 GMT

Yes,my central is a custom board,and it is able to connect to several other devices.

From the sniff I posted,we can see that the only difference is the CSA and window size/offset. The device has CSA1 in its ADV packet,the phone is smart to use CSA1 in its CONNECT_REQ, but my central still use CSA2.

I'm not sure about how CSA works in connection procedure.I suppose If I copy the phone parameters to my central in CONNECT_REQ, there should be no difference as to the device ,right?

RE: central cannot connect to a device, always 0x3e

Vidar Berg — Fri, 28 Apr 2023 06:37:22 GMT

Yes, it is mandatory in Bluetooth 5. But I don't recall seeing this be a problem before. The Softdevice will fall back to using CSA #1 if the peripheral does not support CSA #2 as required by the spec.

Are you testing with a custom board or a DK? And have you tested if it is able to connect to other devices as central or peripheral?

RE: central cannot connect to a device, always 0x3e

daoms — Fri, 28 Apr 2023 03:23:47 GMT

not really.I'm suspecting it is the CSA problem,as we can see the device ADV packet show it is CSA 1.

Is there a way to change the ChSel of my 52832 from 2 to 1?

I searched in forum here, and get the awareness of that CSA 2 maybe is mandatory....hope not.

RE: central cannot connect to a device, always 0x3e

Vidar Berg — Thu, 27 Apr 2023 12:29:53 GMT

Hi,

The peripheral is either failing to receive the connect ind packet or ignoring it (most likely the latter if the issue is consistent). Do you know if the peripheral might be advertising with a whitelist/filter accept list? When advertising with a whitelist, the peripheral will only respond to connect request from known devices in the list.

Best regards,

Vidar