CC2642R: Two issues on Connection Parameter Request procedure

Hi,

I'm assigning an expert to comment. Stay tuned for follow-up.

Hi Cetri,

I will try to reproduce here. What phone model and android version were you using?

Do you have a sniffer log of this?

Hi Marie,

My phone is ZTE Z978 with Android 6.0.1.

The sniffer log is already attached in my original post.

Can you check the LL source code to see what I'm asking?

- Cetri

Hi Cetri,

I would say the second packet violates the following paragraph in the spec: ( BLUETOOTH SPECIFICATION Version 5.0 | Vol 6, Part B page 2670 Link Layer Specification 5.1.7.1 Issuing an LL_CONNECTION_PARAM_REQ PDU).

• May set the Offset0 to Offset5 fields to a value other than 0xFFFF [...] If one or more of the Offset0 to Offset5 fields have been set, then:
[...]
- If Interval_Min is not equal to Interval_Max then the PerferredPeriodicity
field shall be set to a value other than zero. If Interval_Min is equal to
Interval_Max then the PreferredPeriodicity field may be set to any value
and shall be ignored by the recipient.

However I agree with your second point, that when this happens the master should get a GAP_LINK_PARAM_UPDATE_EVENT with status != success.

Hi Marie,

Thanks for your reply. Per your pointing to the spec, I agree that my Android used an invalid parameter.

Have you reported the issue of the lack of GAP_LINK_PARAM_UPDATE_EVENT upon rejection to the development team? Is there any way to know if a rejection has happened?

- Cetri

Hi Cetri,

Yes I have scheduled a discussion with the development team on this topic. I will let you know by the end of next week.

Since your device is the master in this connection you should be able to use an L2CAP connection update parameter procedure instead. If you disable the LL Connection Update Request on the device this will happen automatically when you call GAP_UpdateLinkParamReq().

uint8_t features[8];
uint8_t i;

 
features[0] = (
                LL_FEATURE_ENCRYPTION
               //|LL_FEATURE_CONN_PARAMS_REQ
               | LL_FEATURE_REJECT_IND_EXT
               | LL_FEATURE_SLV_FEATURES_EXCHANGE
               | LL_FEATURE_PING
               | LL_FEATURE_DATA_PACKET_LENGTH_EXTENSION
               | LL_FEATURE_PRIVACY
               | LL_FEATURE_EXTENDED_SCANNER_FILTER_POLICIES
              );

 
for(i=1; i<8; i++)
{
    features[i]=0;
}
HCI_EXT_SetLocalSupportedFeaturesCmd(features);

Hi Marie,

L2CAP Connection Parameter Update Request can be sent by only slave, not master according to the spec 5.1 Vol 3 Part A Section 4.20 : 

Hi Marie,

What I want to do is to connect with a phone with a short interval to discover services/chars quickly and then switch to a longer interval to save power. If I reconnect, I will have to do discovery again since the phone may come up with different handles upon the new connection. That means I should use a short interval for the new connection and switch to a longer one again, which will lead me to the same result.

If I can know whether or not the connection parameter update has failed, I can re-attempt with different parameters that the phone may accept. Any update from the development team?

- Cetri

Hi Cetri,

I see. I will let you know later this week.

From your log it looks like the phone did accept the parameters, it just added the offset value which makes it an invalid request...