Android Question BLE - Scan Request and Scan Response?

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doncx

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When I use SCAN or SCAN2, I receive the standard advertising packet in response. It's helpful, but the device offers more.

The BLE device I'm communicating with (a Blue Maestro Tempo Disc) has this standard advertising packet - which I'm receiving - and also a "scan response" packet with further information, which they say is available to a "scan request".

How do I issue a "scan request"? I have not figured this out.

Thanks for any information on this.
 
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emexes

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doncx said:
and also a "scan response" packet with further information, which they say is available to a "scan request".

How do I issue a "scan request"?
Click to expand...

Maybe their usage of the word "scan" at that point means for their sensors to take a measurement, rather than from our perspective at the other end of the communication where we're thinking it's a Bluetooth scan to see who's out there.

Try connecting up with nRF Connect, see what characteristics (measurement and status values) are available.
 
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emexes

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doncx said:
Thanks for any information on this.
Click to expand...

It's been a few years since I looked at BLE GATT, and the consortium seems to have rearranged their website yet again.

I think the most useful documentation, for deciphering GATT descriptors that tell you the type, format and units of each characteristic, is now at:

https://www.bluetooth.com/specifications/assigned-numbers/

and I've attached the most useful document from there. No, I take that back: apparently it's too large to attach to this post. Download "GATT_Specification_Supplement_v7.pdf" and search for "blood" or "pulse" or "pressure" or whatever it is your device is measuring.
 
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emexes

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doncx said:
How do I issue a "scan request"? I have not figured this out.
Click to expand...

If the device has a "take reading now" button, you might not even have to request the device to do a reading; there's probably a characteristic (data value) that tells you the last valid reading, and perhaps its date and time.

So you could do it the hacker way - read all characteristics (you get a list of services when you connect, and then for each service you can get a list of characteristics) and see what changes when you do a new reading (with a different value to the old reading). But nRF Connect is already set up to do almost that, except that you'll have to poke through the characteristics one-by-one instead of having them all displayed in real(ish) time. Might be quicker to use that than to write your own.
 
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doncx

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Thanks for your replies. I am new to BLE and so am learning as I go. I believe there is a formal "scan request" and "scan response" capability in BLE where the requestor (B4A in this case) scans with a "request" and receives additional *advertising* information - without connecting - from devices with that capability.

However, for all my searching I haven't figured out exactly how. Here's a link that describes the BLE feature: https://www.argenox.com/library/bluetooth-low-energy/ble-advertising-primer/.

Search that page for the subheading "Scan Response" to find this:


When I scan with B4A I see the normal advertising in my logs but nothing additional. How do I access that?

All help is appreciated!
 
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