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Smart Bluetooth

LeCa_2156671
New Contributor II

Hi experts,

  How we set/config the SCA/MCA for BLE connection in BCM20736? Is there any interface or API we could use for this setting ?

  tks

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1 Solution
BoonT_56
Employee

I will close this case for the time being while you work out with ITON.

View solution in original post

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17 Replies
BoonT_56
Employee

Sorry, but what are SCA and MCA?

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LeCa_2156671
New Contributor II

SCA -- Slave clock accuracy

MCA -- Master clock accuracy

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LeCa_2156671
New Contributor II

SCA -- Slave clock accuracy

MCA -- Master clock accuracy

When create connection between master/slave, the clock accuracy parameter would be sent from master to slave in the connection request package.

We need to modify/config this parameter.

tks

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BoonT_56
Employee

My understanding is that during a connection, the master will share a frequency hop synchronization packet with its slave which contain information of its bd_address and clock. That is how a slave in turn get synchronized with the master as well as the frequency hopping algorithm. I am not aware that there is an API to change these parameters.

Are you facing some issues like connection or reconnection?

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LeCa_2156671
New Contributor II

Hi Boont,

   Yes we do have the issue of unstable connection / re-connection.

   Due to our experience, we doubt that it's related to the clock accuracy when we using the internal LPO now.

   We want to modify the MCA parameter to 1200ppm and do further test.

   But we could not find out the interface or API.

   Could you pls help us to confirm with Designer/Developer for our above requirement ?

   Many thanks

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LeCa_2156671
New Contributor II

Hi Boont,

When using internal clock,the real accuracy of the clock is 1200ppm,but we trace the air data using analyzer and found the SCA in the connection request packet 20736[Central] send is 31ppm~50ppm.

And  we found a smart phone with a smaller clock accuracy is easier to lost connection with 20736.

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BoonT_56
Employee

Are you using a module or SoC? Yes, the internal LPO (128KHz) has an accuracy of 1200ppm.

Do you have any air trace or log to show the disconnection scenario?

I'm checking internally on the APIs.

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LeCa_2156671
New Contributor II

Hi boont,

In out test, BCM20736 works as master, cell-phone works as slave.

Please find out the picture, the log file cached by sniffer.

In Link-Layer Packet, the SCA (clock accuracy ) announced as 31ppm ~ 50ppm. it's fixed setting and no APIs for us to modify.

link.pngdescription.png

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BoonT_56
Employee

I have just confirmed with the developers that we do not have APIs to control this these parameters nor are they open to change anywhere. Btw, what is the model of the cellphone that you are using? And OS?

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LeCa_2156671
New Contributor II

Hi Boont,

   The cell phone is Moto Z.

   We do need the APIs to modify the SCA/MCA parameters, we have purchased nearly 200K BCM20736. it's absolutely a bug of setting when BCM20736 work with internal LPO.

   Pls help confirm with developers again.

   tks

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LeCa_2156671
New Contributor II

Hi Boont,

   Could the developers provide one patch to us, which could modify the MCA/SCA to 1200ppm when we define internal LPO used.

   It's very important for us, and count on your strong support.

   Many thanks...

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BoonT_56
Employee

I have some thoughts here:

1) Did you try on other mobilephones with similar Android ver?

2) Assuming you are using SoC (not module), did you have a chance to test it out on the tag3? What did you see then?

3) On the disconnection issue, does it help if you increase the duty cycle of the scan interval and window?

4) From whom (in Cypress) did your procurement/sales work with?

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LeCa_2156671
New Contributor II

Hi Boont,

please help refer to my answer as below:

1) Did you try on other mobilephones with similar Android ver?

--> Yes we did the compare test.  Seems that the error phenomenon only related to the cell-phone. The higher accuracy clock of the cell-phone, the shorter time of the connection broken.

2) Assuming you are using SoC (not module), did you have a chance to test it out on the tag3? What did you see then?

--> We have no tag3 on our hand, so we could not do the same test. sorry for that.

3) On the disconnection issue, does it help if you increase the duty cycle of the scan interval and window?

--> In our system design, we could not decrease the interval of the connection. Scan interval is no related to connection interval.

4) From whom (in Cypress) did your procurement/sales work with?

--> Iton in Shenzhen

One more thing for your reference.

When we design with another BLE SoC, they have the same issue(Default MCA/SCA setting is 31ppm ~ 50ppm). With this setting, the connection would break after few minutes.

But they provide us the MCA/SCA setting API, after we modify the setting to the right data(refer to clock accuracy), the issue of disconnection is solved. Very stable.

For your reference.

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BoonT_56
Employee

Your request to change "MCA/SCA" settings, if possible, would have to happen on FW level. It is not something that Apps can do. Moreover, this issue occurred to only one particular brand of mobilephone. My advice is to get your management to talk to ITON about this issue. Then ITON may seek counsel with Cypress.

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LeCa_2156671
New Contributor II

Hi Boont,

   Thanks for your advice, I would push ITON to seek counsel wih Cypress ASAP.

   So, if there is one solution could be provided by Cypress, it's one patch ? or some others ?

   tks

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BoonT_56
Employee

Actually I haven't across this request before. So it could be a patch as you said...

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BoonT_56
Employee

I will close this case for the time being while you work out with ITON.

View solution in original post

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