rSAP GPRS modem support

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eddie_f
Posts: 30
Joined: Sun Apr 17, 2011 6:39 pm

rSAP GPRS modem support

Post by eddie_f » Mon May 09, 2011 6:58 pm

VW/Skoda/Audi (and maybe others too) do have a feature called GPRS modem (and 3G in newer rSAP modules) within their BT modules. The idea is to supply all BT enabled devices of the passengers in the car with mobile internet. With modern smartphones, an internet connection is often used to check mail, weather, traffic (that's my primary usage when driving, traffic info for my Navgion Mobile Navigator for Android)...

On Windows Mobile 6.5 I had the possibility to use the GPRS modem via another BT connection from my phone to the car. This works like a modem dialup connection, where phone dials *99# to get an internet connection over the BT modem.
I already checked the android market, but there seems to be no such app available. All tethering apps work the other way round and are for laptops, that use the phone as their BT modem or even as a Wifi hotspot.

This could be an interesting feature for a future version to make the phone "whole" again when the SIM is borrowed to the car kit.
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Thanks for the DUN plugin, you are the best!

admin
Site Admin
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Joined: Wed Mar 23, 2011 4:12 pm

Re: rSAP GPRS modem support

Post by admin » Tue May 10, 2011 9:47 am

Good idea but I guess I will not find the time to do that and I don't have a car to test it.

As this is outside the scope of rSAP anyway perhaps someone else might try? After all Android is only Linux so all necessary parts (rfcomm?) may be there - at least on Cyanogen. Perhaps all it needs is a script?

snudel
Posts: 9
Joined: Mon May 02, 2011 1:59 pm

Re: rSAP GPRS modem support

Post by snudel » Tue May 10, 2011 3:37 pm

Hi Admin

Maybe you post where you are living. Maybe someone with a car can help you testing it.
I am also interrested in this topic.

Rgds

eddie_f
Posts: 30
Joined: Sun Apr 17, 2011 6:39 pm

Re: rSAP GPRS modem support

Post by eddie_f » Tue May 10, 2011 4:24 pm

There is an app on the market called "Nook Color Bluetooth Tether" that does exactly what I need, but it does not work on the DZ, because the widget that initates the connection cannot be started or even found (maybe CM7 related or Sense does not like the widget whatever). Maybe someone with CM7 running on the DZ/DHD can try the app?
I don't want to switch from Sense to whatever ROM, I like it the way it is.

The BT modem function can be emulated by any laptop/desktop computer with a widcomm BT stack, so there is no need for a car with that function. I would much appreciate it, if someone with the right coding skills could look into that or point me towards an app, that I haven't seen yet. Linux can definitely do that.

-EDIT:

Found this on XDA:

Code: Select all

find out Bluetooth device id and channel ID
enable root (su)

to find out BT <device id>:
hcitool scan --class

to find out <channel>
sdptool search -bdaddr <BT device id>:

To bind to rfcomm0
rfcomm bind /dev/rfcomm0 <bt device id> <channel>

If it works (the dialing part is missing here AFAIK), this included in a nice app (or in the rSAP app) could do it already.

-EDIT 2:

Tried two different things and nothing seems to work. Looks like the rSAP app sets the phone into a kind of airplane mode but with bluetooth enabled. Now I can't connect to any new device. The GPRS modem is only available after the rSAP connection is up, so this looks like a dead end right now. No internet for the Android phone when in rSAP mode. The funny thing is, that I can use my old WM6.5 device and connect to the internet using the GPRS modem.

On the other hand, the radio can download the phonebook via PBAP in rSAP mode. Damn you Google for not having DUN included into Android, this could have been so easy :cry:
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Thanks for the DUN plugin, you are the best!

admin
Site Admin
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Joined: Wed Mar 23, 2011 4:12 pm

Re: rSAP GPRS modem support

Post by admin » Wed May 11, 2011 9:57 am

The problem is again that it may not work with the HTC/Broadcom Bluetooth stack. At least all the hcitool, sdptool and rfcomm might not work. I'll check the "Nook Color" app this evening.

I don't understand why HTC does not use the standard Bluez code...

eddie_f
Posts: 30
Joined: Sun Apr 17, 2011 6:39 pm

Re: rSAP GPRS modem support

Post by eddie_f » Wed May 11, 2011 3:02 pm

Maybe they use Broadcom hardware for BT and Bluez has problems with Broadcom stuff (stability or driver issues). I haven't tried CM for my phone, so I can't say if there are any problems with BT when it's in use.
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Thanks for the DUN plugin, you are the best!

admin
Site Admin
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Joined: Wed Mar 23, 2011 4:12 pm

Re: rSAP GPRS modem support

Post by admin » Wed May 11, 2011 11:15 pm

What's puzzling me is that when you flash CyanogeMod (or another AOSP based ROM) you have a completely different Bluetooth stack, and it works. Perhaps it's worth the effort to try and extract the HTC/Broadcom stuff from the HTC ROMs and replace it with "pure" Bluez from AOSP?

Did not check the Nook app yet...

admin
Site Admin
Posts: 4128
Joined: Wed Mar 23, 2011 4:12 pm

Re: rSAP GPRS modem support

Post by admin » Thu May 12, 2011 9:59 pm

OK did a test with my CyanogenMod Desire connecting to my Galaxy S. I typed

Code: Select all

rfcomm bind /dev/rfcomm0 <Galaxy S device id> <channel>
pppd /dev/rfcomm0
When starting pppd I get the pairing hints and the Galaxy S asks me if I want to allow DUN access from the Desire. But I still don't have network access. Does any Linux guru know what's missing? Some script? Is it possible that I ned the 'chat' util?

eddie_f
Posts: 30
Joined: Sun Apr 17, 2011 6:39 pm

Re: rSAP GPRS modem support

Post by eddie_f » Fri May 13, 2011 1:20 am

I found this: http://www.eit.se/hb/misc/text/ipaq_gprs_bluetooth.txt

You need the chat utility and all steps are described in there. It's for an ipaq, but it's dialed from a linux distro on the ipaq ;)
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Thanks for the DUN plugin, you are the best!

admin
Site Admin
Posts: 4128
Joined: Wed Mar 23, 2011 4:12 pm

Re: rSAP GPRS modem support

Post by admin » Fri May 13, 2011 10:39 am

Found source code for 'chat'. I think I'll try that over the weekend. Can anyone think of a use case where you might want to connect to a different device than the car kit for DUN connection? I don't want to implement a device selection, that takes so much time to code :D

As a former Microsoft afficionado I'm really beginning to like Linux...

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