Ok I got the car's hotspot working, this is not particularly intuitive!
I have two phones, a Galaxy A5 2016 (personal) and an iPhone 6s (work). The A5 is the primary phone and the one I want to use for data because I get 17GB a month on it and use hardly any of it.
It was definitely connecting via HFP rather than rSAP, here are some before and after pics:
First, if I try and connect to the wifi hotspot with the iPhone, I get this error:
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I believe this is because the car is trying to use the embedded SIM by default which doesn't have a data pack.
I checked the Bluetooth settings on my Samsung out of curiosity (I wanted to see what changes):
Screenshot_20171116-094631.jpg
Now for the fun part... go into connection manager:
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On the primary phone go into the options menu:
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Select "Display Bluetooth profiles":
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Notice how car phone says "Not connected". Select it and the phone will go "boing!" (well mine does due to the notification settings), then you'll get this message:
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Select "No" and you will now be using your phone for data via rSAP:
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Notice how car phone says "connected" but handfree (HFP) is now "not connected".
Back on connection manager we can see that the data connection is now using my phone rather than the eSIM:
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Now looking at the Bluetooth settings on the Samsung it's disabled "call audio", I've not actually tried making a call yet but suspect it'll work fine (my Passat also uses rSAP and only has "Contact access" and "SIM card access" listed and works fine):
Screenshot_20171116-094730.jpg
Ok so now I connected the iPhone to the car's wifi hotspot and voila!
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You may think "jeez, just enable the wifi hotspot on your phone" but I didn't want to have to keep turning that on and off as it saps the battery (and is a security risk). This way the kids tablets will auto-connect to the car wifi whenever they get in and all the data will get routed via the rSAP connection to my Samsung.
Now I haven't checked if it connects like this automatically next time I jump in, I'm hoping that the Bluetooth connection settings are "sticky" but we'll see when I jump in to pick up the kids later whether I get the tell tale "boing!" (which means it connected via rSAP rather than HFP).
If you haven't worked it out yet, I work in IT and am a bit of a nerd so quite like playing with stuff like this! :-)