scan request and scan response

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luke.liu@litepo...
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scan request and scan response

From your document Proximity application_v.13, it seems that central device sends connection request right after receiving the advertisement packet from peripheral device. But according to BT4.1 spec, there shall be scan request packet from central device and scan response packet from peripheral device before the connection request packet. Do I miss something here? Thanks.

Luke

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Hi luke,

Hi luke,

The da14580 complies with the BT4.0 specification. If the scanning is passive and not active then there are no scan response data. In case of active scanning for every advertising indication a scan response is requested from the central, if you mean that you can't see the command that sends the scan response data is because those are sent from lower layers of the stack. You use a sniffer and you can't see scan response data packets ?

Thanks MT_dialog

luke.liu@litepo...
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Can you check the document

Also from your GUI SmartSnippets, how do I mimic the two device connection? I tried to use the data rate monitor with two devices. Once I started peripheral and central, I was not able to sniffer either the scan request or the scan response during the scanning process. After he scanner finds the device address when I click connect I did sniffer the connection request packet.
Thanks.

luke.liu@litepo...
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For the above question, I was

For the above question, I was able to use the connection manager to mimic the link with both passive and active scan. I got scan request and response with active scan.
I do have another question about the air interface. It seems the T_IFS (time between adv and scan request) allowed is about 125-140us. According to spec, the T_IFS time shall be 150us. But I tried with 150us it definitely does respond to the scan request. Do you know what is the designed intervals?

Thanks,
Luke

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Hi luke,

Hi luke,

How do you know that the T_IFS allows 125 - 140 us ? and how did you change the value of the T_IFS? Can you give more information about what you are trying to do?

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luke.liu@litepo...
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Basically our instrument

We sniffer the link. We can fine tune the timing between the falling edge of the advertisement and the scan request.

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Hi luke,

Hi luke,

Because i haven't fully undestood your question....is it why the da listens too early 125-140 us and not exactly at 150 us ? This is because the system needs to have some kind of tolerance. 

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luke.liu@litepo...
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Yes your understanding is

Yes your understanding is right. I understand the tolerance but if scan request is sent at 150us, the da will miss it.

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Hi luke,

Hi luke,

The BT specification states that Scan_Request shall be sent after 150 us and the tolerance is defined as the tolerance of the fast clock in terms of ppm. The Scan_Response is also sent after 150 us form Scan_Request. To enable tolerance of the clocks 580 starts its receiver earlier than 150us.

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luke.liu@litepo...
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I understand 580 starts

I understand 580 starts receiver earlier than 150us. But it seems to shut down its receiver before 150us. That's why in my previous comment I said by playing with the scan request timing, the scan request is only received (confirmed by the scan response packet) in the window 125-140 us after the advertisement. Not 150us as in spec.

luke.liu@litepo...
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any comments?

any comments?

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Hi luke,

Hi luke,

We will get back to you as soon as we 've got some new information on this.

Thanks MT_dialog

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Hi luke,

Hi luke,

Can you give us some clarifications about the issue you are experiencing, for example is this happening with multiple da chips, is it something you are experiencing every time (is it replicable) or it happens from time to time, what devices are you using and which SDK you are using, any information would be usefull. This seems a bit strange because an issued like that would be hard to miss since the da have interoperability with most of the major vendors. Any information you can provide it would be useful to us.

Thanks MT_dialog 

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