CC2541 can't update S120 connection parameters

RE: CC2541 can't update S120 connection parameters

Hung Bui — Wed, 18 Mar 2015 10:28:56 GMT

@bihu: It depends on what you implemented on the nRF51 central. Have you called sd_ble_gap_conn_param_update() anywhere in the nRF51 central firmware? There are 2 cases:

The central actively update the connection parameter without any request.
The central receive the request from the peripheral (BLE_GAP_EVT_CONN_PARAM_UPDATE_REQUEST event) then update the connection parameter accordingly.

In both case, sd_ble_gap_conn_param_update() must be called in the nRF51 central firmware.

RE: CC2541 can't update S120 connection parameters

bihu — Tue, 17 Mar 2015 15:15:02 GMT

Both peripheral and central role device are TI CC2541, I call GAPRole_SendUpdateParam on peripheral role device, I can see the LL_CONNECTION_UPDATE_REQUEST. But I can't see the update packet when central device change to NRF51822. How to explain this problem? I also use the latest TI stack.

I will try the S110 stack and try to update the connection interval to find the difference. I will tell you if I found clues.

RE: CC2541 can't update S120 connection parameters

Hung Bui — Tue, 17 Mar 2015 14:25:10 GMT

@bihu: It's correct that the scanning period will drop any connection packet inside that period. However, this only happens when the scan window is large and conflict with connection event. You would need to adjust the scan windows so that it won't block all the connection event.

No, the TI device when working as peripheral can't send LL_CONNECTION_UPDATE_REQUEST, what it can send is Conection parameter update request on L2CAP layer (Logical link controla and Adaption protocol). The LL_CONNECTION_UPDATE_REQUEST is on link layer and it should be from the master.

RE: CC2541 can't update S120 connection parameters

bihu — Tue, 17 Mar 2015 11:56:25 GMT

I'm sorry that makes you confused. From the Figure 16 in S120_Softdevice_Specification_V1.0.pdf. I found the S120 can't send data packet when doing scanning. I know the S120 can set the connection parameters when establish the connection. My confuse is the TI's peripheral device can't send LL_CONNECTION_UPDATE_REQ.

RE: CC2541 can't update S120 connection parameters

Hung Bui — Tue, 17 Mar 2015 11:50:11 GMT

What the peripheral can do is to set it's preferred connection parameter so that the central device can read and update accordingly if the central wants. Or the peripheral can send the connection parameter request (it's not the same as LL_CONNECTION_UPDATE_REQ) if the central accept that it will send LL_CONNECTION_UPDATE_REQ to update the connection parameter that justified with the request from peripheral. You can have a look here.

RE: CC2541 can't update S120 connection parameters

Hung Bui — Tue, 17 Mar 2015 11:48:19 GMT

I am sorry that I don't really get what you meant in "The BLE S120 will not send the packet when doing scan. And I saw the packet was sent after 50ms that I set as default connection interval. After I set the connection parameters when establish the connection and not scan when send data."

How the connection parameter is set in BLE is that, the central set the connection parameter (interval, timeout, slave latency) when it sends the connect request (when the connection is established). If there is no change, this connection parameter will be used all the time. The central and only the central can change this connection parameter by sending the LL_CONNECTION_UPDATE_REQ.

RE: CC2541 can't update S120 connection parameters

bihu — Tue, 17 Mar 2015 01:46:53 GMT

I think I ignore the time line on S120 document. The BLE S120 will not send the packet when doing scan. And I saw the packet was sent after 50ms that I set as default connection interval. After I set the connection parameters when establish the connection and not scan when send data. But my application can't set the connection interval when establish the connection for the chip didn't send the data all the time. Do you think the peripheral device didn't send LL_CONNECTION_UPDATE_REQ is the TI's bug?

RE: CC2541 can't update S120 connection parameters

Hung Bui — Mon, 16 Mar 2015 16:22:54 GMT

I just have another look in the S120 v2.0.0 APIs. We do have the compability mode for legacy devices. Could you try to use the opt api sd_ble_opt_set() with the compat_mode set to 1.

RE: CC2541 can't update S120 connection parameters

Hung Bui — Mon, 16 Mar 2015 15:38:42 GMT

@bihu: Preferred connection parameter update should be set on the peripheral not on the central side.

We had the issue with CC2541 with older stack from TI before, that the TI chip doesn't accept connection parameter update with tx windows offset set to 0. In the newer TI stack it works though.

However, what you described it a little bit different where the S120 didn't sent LL_CONNECTION_UPDATE_REQ. Have you made sure the connection parameter update request is accepted by the S120 ?

Could you send me the sniffer trace that shows the issue ? Also please let me know your S120 version.

RE: CC2541 can't update S120 connection parameters

bihu — Mon, 16 Mar 2015 03:52:46 GMT

And I tried to call sd_ble_gap_ppcp_get and sd_ble_gap_ppcp_set. The return error code is 6 (Not Supported). How to update connection interval on S120 side?