CC2640R2F: Questions on connection parameter update

Niranjan Hegde

Part Number: CC2640R2F

Device	CC2640R2LAUNCHXL
SDK	simplelink_cc2640r2_sdk_4_20_00_04
IDE	IAR8.32.2
Reference Project	MultiRole

Hi Ti,

Recently we have faced some issue with the connection interval https://e2e.ti.com/support/wireless-connectivity/bluetooth/f/538/t/943355.

I have multiple questions as listed below.

1. Connection interval update call-back never received to application.

As per the suggestion, we have used "GAPROLE_LINK_PARAM_UPDATE_APP_DECIDES” to update the connection interval where application need to receive call back in the “GAP_UPDATE_LINK_PARAM_REQ_EVENT”.

But unfortunately I couldn’t receive this event at all. I was always getting just the “GAP_LINK_PARAM_UPDATE_EVENT”.

Could you please let me know when this event will triggered? (Like in LL_CONNECTION_UPDATE_IND etc).

Update in Multi.c

// Connection parameter update parameters.

static gapRole_updateConnParams_t gapRole_updateConnParams =

{

.paramUpdateEnable = GAPROLE_LINK_PARAM_UPDATE_APP_DECIDES, //<< updated on suggestion

.connHandle = INVALID_CONNHANDLE,

.minConnInterval = DEFAULT_MIN_CONN_INTERVAL, //<< set to 50 (ms I guess)

.maxConnInterval = DEFAULT_MAX_CONN_INTERVAL, //<< set to 60 (ms I guess)

.slaveLatency = MIN_SLAVE_LATENCY,

.timeoutMultiplier = DEFAULT_TIMEOUT_MULTIPLIER

};

2. Multiple defines related to connection interval and connection update intervals

There are multiple connection interval related parameters (like #defines and update structures).

As I can see there are multiple structures for connection parameter updates as in below files:

multi_role.c - gapRole_updateConnParams_t updateParams
multi.c - static gapRole_updateConnParams_t gapRole_updateConnParams

As I can understand “gapRole_updateConnParams” is only used in “gapRole_HandleParamUpdateNoSuccess” which will be called on the connection param update timeout.

Could you please let me know the uses of different structure and the use of timeout? In other cases (than the timeout) it will not use the param update enable to “GAPROLE_LINK_PARAM_UPDATE_APP_DECIDES”.?

Also there are some unused #defines in multi.c like “MIN_CONN_INTERVAL” and “MAX_CONN_INTERVAL”, even project compiles without them.

3. Multirole project will automatically choose higher connection interval (above the defined).

As I observed, on connecting a two Mutirole devices will not do any transactions for “LL_CONNECTION_UPDATE_IND” (unless connection update option used).

In mult_role.c I have set the “DEFAULT_CONN_INT” to 55 (I guess unit is 55 ms). Other Multirole was flashed with DEFAULT_CONN_INT to 200 which is initiating the connection.

After the connection as observed, "connection interval" will be 250ms.

I was expecting it to be around 50 - 60.

4. Multirole project connection interval param update value has no relevance with one set to GAP, while connecting with Android.

(Similar to above question 3).

I also observed the connection interval with the Android mobile phone.

In mult_role.c I have set the “DEFAULT_CONN_INT” to 55 (I guess unit is 55 ms).

But after the connection param update the value has been set to 36.

I was expecting it to be in the range of 55. (50 – 60)

Not sure why?

Could you please educate me on all of the questions I have? Also let me know if you need any further information.

Thanks in advance.

Niranjan Hegde

over 4 years ago

0 Jenny T over 4 years ago

TI__Expert 4435 points

Hi Niranjan,

I've assigned an expert to assist you with your questions.

Best Regards,

Jenny

0 Alec May over 4 years ago in reply to Jenny T

TI__Genius 17265 points

Hi Niranjan,

I'd be happy to help look into this issue for you. The first bit of advice that I can give is that the connection interval is measured in units of 1.25ms according to the BLE core spec. So the minimum conn interval value of 6 indicates the minimum BLE connection interval of 7.5ms. I will look into your questions about the GAP events and get back to you.

Best Regards,
Alec

0 Niranjan Hegde over 4 years ago in reply to Alec May

Intellectual 650 points

Hi Alec,

Thanks for clarifying on the connection interval multiplier. I had to ask this question as I couldn't able to relate some of the comments written for those values.

As example of multi.c

Thanks in advance and Happy holidays !

Niranjan

0 Alec May over 4 years ago in reply to Niranjan Hegde

TI__Genius 17265 points

Hey Niranjan,

So help me understand, is all of this on one device? The event GAP_UPDATE_LINK_PARAM_REQ_EVENT is only posted when you RECEIVE a param update request, not when you initiate one. You can see that in the documentation here:
http://software-dl.ti.com/simplelink/esd/simplelink_cc2640r2_sdk/3.40.00.10_new/exports/docs/blestack/ble_user_guide/doxygen/ble/html/group___g_a_p___event___i_ds.html

Best Regards,
Alec

0 Niranjan Hegde over 4 years ago in reply to Alec May

Intellectual 650 points

Hi Alec,

Happy new year.

As I have mentioned in questions 1 & 4 (Initial questions), I am initiating the connection param update from the other device while DUT(device under test) "receives" param update request..

0 Alec May over 4 years ago in reply to Niranjan Hegde

TI__Genius 17265 points

Hey Niranjan,

Thanks for clearing that up. Do you have GAP_UPDATE_REQ_PASS_TO_APP set? I believe if it is not set that the update process will be handled entirely by the stack itself. You can see this described at the link below. Let me know if this helps.

software-dl.ti.com/.../group___g_a_p___constants.html

Best Regards,
Alec

0 Niranjan Hegde over 4 years ago in reply to Alec May

Intellectual 650 points

Hi Alec,

As mentioned in question 1, I am using the GAPROLE_LINK_PARAM_UPDATE_APP_DECIDES.

http://software-dl.ti.com/lprf/simplelink_cc2640r2_sdk/1.30.00.25/exports/docs/blestack/ble_sw_dev_guide/doxygen/group___multi___c_bs.html

May be I missed to mention that we are using BLE4.2 not BLE5.

Thanks

Niranjan

0 Alec May over 4 years ago in reply to Niranjan Hegde

TI__Genius 17265 points

Hi Niranjan,

Sounds good, what does your param update decision callback look like?

Best Regards,
Alec

0 Niranjan Hegde over 4 years ago in reply to Alec May

Intellectual 650 points

Hi Alec,

Please refer the Multirole project. Have not changed other part of the code. So my call back is as is. Point here is I am not getting this call-back at all.

static void multi_role_paramUpdateDecisionCB(gapUpdateLinkParamReq_t *pReq,
                                             gapUpdateLinkParamReqReply_t *pRsp)
{
// Make some decision based on desired parameters. Here is an example
// where only parameter update requests with 0 slave latency are accepted
if (pReq->connLatency == 0)
{
    // Accept and respond with remote's desired parameters
    pRsp->accepted = TRUE;
    pRsp->connLatency = pReq->connLatency;
    pRsp->connTimeout = pReq->connTimeout;
    pRsp->intervalMax = pReq->intervalMax;
    pRsp->intervalMin = pReq->intervalMin;
}

// Don't accept param update requests with slave latency other than 0
else
{
    pRsp->accepted = FALSE;
}
}

Thanks

Niranjan Hegde

0 Alec May over 4 years ago in reply to Niranjan Hegde

TI__Genius 17265 points

Hey Niranjan,

Just an update, I'm discussing this with someone else on my team to come up with some recommendations for you. I will provide an update tomorrow.

Best Regards,
Alec

0 Alec May over 4 years ago in reply to Alec May

TI__Genius 17265 points

Hey Niranjan,

We're working with your field applications representative now to get a better idea of the full picture here, but in the meantime we found another thread that I think may be related to your current issue. Take a look at it and let me know your thoughts.

https://e2e.ti.com/support/wireless-connectivity/bluetooth/f/538/t/842051?CCS-CC2640R2F-%D0%A1onnection-interval-update#pi320995=2

Best Regards,
Alec

0 Niranjan Hegde over 4 years ago in reply to Alec May

Intellectual 650 points

Hi Alec,

Thanks for your reply,

As suggested in the link I have defined USE_LL_CONN_PARAM_UPDATE and I could see the application call back for connection param update with "GAP_UPDATE_LINK_PARAM_REQ_EVENT". Thanks for the pointing out the solution.

But still question 3 is open.

Meanwhile I will continue my testing.

Thanks

Niranjan Hegde

0 Clément over 4 years ago in reply to Niranjan Hegde

TI__Guru** 101450 points

Hey Niranjan,

Niranjan Hegde said:

3. Multirole project will automatically choose higher connection interval (above the defined).

As I observed, on connecting a two Mutirole devices will not do any transactions for “LL_CONNECTION_UPDATE_IND” (unless connection update option used).

In mult_role.c I have set the “DEFAULT_CONN_INT” to 55 (I guess unit is 55 ms). Other Multirole was flashed with DEFAULT_CONN_INT to 200 which is initiating the connection.

After the connection as observed, "connection interval" will be 250ms.

I was expecting it to be around 50 - 60.

Quoting the BLUETOOTH CORE SPECIFICATION Version 5.1 | Vol 6, Part B, §4.5.1:

The connInterval shall be a multiple of 1.25 ms in the range of 7.5 ms to 4.0 s.
The connInterval is set by the Initiator’s Link Layer in the CONNECT_IND or
AUX_CONNECT_REQ PDU from the range given by the Host and can be
changed using the Connection Update procedure (see Section 5.1.1) or
Connection Parameters Request procedure (see Section 5.1.7).

I guess the connection interval used at connection establishment is within the expected range. Then, after a short amount of time a connection parameter is issued and accepted by the peripheral hence this longer connection interval. You could verify this using a BLE sniffer. You could also reject all the connection parameters updates on both devices to see if the connection interval remains the same.

I hope this will help,

Best regards,

Bluetooth®︎

Bluetooth forum

CC2640R2F: Questions on connection parameter update