6 ms·

Faking Bluetooth LE

110 points by tdrnd 13y ago

acgourley 13y ago
This is awesome! The 2.4ghz nordic RF chip is cheap and easy to work with, I could imagine the guts of a simple "FitBit" style device made for just $5 at 'maker scale' of 1,000+ units. The ability to talk to android/ios phones cheaply will lead to some really cool projects. Obviously if you're going commercial you have so many other hurdles to cross that you may as well just use BTLE proper, but for hacking/making/prototyping it's very cool.
- FigBug 13y ago
  Why not just use a Nordic nRF51822 that comes with a full BLE stack, 32 arm processor, super low power. $2.50 per unit instead of using a separate micro and transceiver.
  - acgourley 13y ago
    I guess because I didn't know those were that cheap - I'm out of date on this stuff and remember BT3.0 SoC's costing a lot more.
  - krasin 13y ago
    In order to use BLE stack in nRF51822, one will need to deal with their DRM for the S110 SoftDevice, or implement an open source BLE stack similar to what the article suggests.
    - FigBug 13y ago
      What DRM is there? I thought the SoftDevice was just a binary blob? I'm currently in the prototyping phase of a product that uses the nRF5, I couldn't see any competitive advantage I would gain from developing my own stack considering the time investment it would take.
      - krasin 13y ago
        Have you noticed that you had to enter a serial number in order to get your SDK?
        FigBug 13y ago
        Yes, is the Sdk somehow locked to the processor serial? How does production work?
        foolsday 13y ago
        The soft device is provided as a hex file and does not contain any DRM whatsoever.
        krasin 13y ago
        Can you post a download url to this hex file? Will the license allow you to do so?
        foolsday 13y ago
        The website requires a Product Key (not serial number) before it allows you to download the installer (I would assume for licensing reasons). The installer also includes documentation and tools that make working with the soft device easier.
        krasin 13y ago
        Thanks for the information. Yesterday, I have bought a few nRF51822, and will update this thread with my experience. While all early signs, including your words, indicate a good possibility that I will hit an unexpected problem due to the licensing scheme, the lack of the first hand experience does not let me be firm in my statements.
lnanek2 13y ago
> It has absolutely nothing to do with bluetooth besides the name Not really true. APIs on Android are mostly the same with a small new set of classes. HTC and Samsung and Broadcom have an API for over a year now and there's an Android standard one in the latest Android announced at Google IO. Enabling and pairing and device discovery are all the same from the Android side, though. Maybe an extra constant indicating the device type. Additionally, it's from the same group as Bluetooth, you often buy adapters and scanners and equipment and test software that are dual mode. This is why BLE is destroying older protocols for the same thing like ANT. ANT was never used much outside a few fitness and medical devices. BLE is all over the place since devices often have a Bluetooth chip in them anyway, so it isn't much more to make it dual mode. Many Android phones support BLE now. Also in that area, the big Bluetooth Unplugfest conference and testing event is there for BLE just like Bluetooth. So all the companies that go to get Bluetooth certified are there with the BLE offerings.
- tadfisher 13y ago
  Unfortunately, the Android BLE API only supports half of the standard, as Android devices cannot be placed in peripheral mode. This is something Apple released on day 1, and it's slightly infuriating when creating cross-platform applications. There is no good, non-hacky way to do local radio comms between iOS and Android, and it stinks. Here's hoping Kit Kat rolls out with full BLE support.
  - JimDabell 13y ago
    > This is something Apple released on day 1 Actually, iOS had support for acting in central mode only in iOS 5 and added support for acting in peripheral mode in iOS 6.
locacorten 13y ago
Another cool hack with Bluetooth from MSR. Emulating a long-lived connection to a smartphone even when the phone is blocking incoming Bluetooth connections: http://research.microsoft.com/en-us/um/people/ssaroiu/publications/mobisys/2009/bluemonarch.pdf http://research.microsoft.com/en-us/um/people/ssaroiu/public...
thethimble 13y ago
Does anyone have any good resources for learning more about BLE?
- Dwolb 13y ago
  I haven't found comprehensive sources. Here's one blog that's good to reference when working with Bluegiga radios.
- onebot 13y ago
  This is the best resource on the subject, written by the designer of the protocol. The author is, surprisingly, a pretty good writer. This not only gives you everything you need to know (without grokking the spec), but also talks a lot about why they made the decisions they did. Highly recommend... http://www.amazon.com/Bluetooth-Low-Energy-Developers-ebook/dp/B009XDA1G8 http://www.amazon.com/Bluetooth-Low-Energy-Developers-ebook/...
  - timthorn 13y ago
    He is also a very good speaker, if you ever get the chance to hear him.
nl 13y ago
Related, Samsung announced that they will be enabling ANT± on all their S4 phones, and apparently the S3 hardware can be enabled too(!) That's big news for anyone doing connected devices.
- stbtrax 13y ago
  It's good for legacy devices, but I can't think of any reason to use ANT in future products since you'd need to have a BLE version for iOS users.
  - nl 13y ago
    Oh, because ANT+ lets you connect to multiple devices simultaneously. BTLE doesn't let you do that, and it's a pretty big problem. For example, if you do triathlons ANT+ lets you use a 910XT for the swim & run, and an Edge 500 for the ride without having to re-pair the devices. This isn't just a theoretical problem: according to a very recent DCRainmaker survey[1] 29% of people use this exact scenario[2]. iOS is bit issue of course, but there are ANT+ dongles and BTLE->ANT+ retransmitters (in the form of a heart rate monitor band). It's worth noting that the Stages power meter does do the dual BTLE and ANT+ transmission thing. I think ANT+ is going to hang around a lot longer than people think, especially in the field above casual fitness. [1] http://www.dcrainmaker.com/2013/09/curiositysurvey-different-cycling.html http://www.dcrainmaker.com/2013/09/curiositysurvey-different... [2] http://www.dcrainmaker.com/2013/10/symposium-keynote-presentation.html http://www.dcrainmaker.com/2013/10/symposium-keynote-present...
    - jmah 13y ago
      Bluetooth LE uses a client/server (called "central" / "peripheral") model; think of "server" like "web server", typically the client is your smartphone. I could believe that a single peripheral can't simultaneously connect to multiple centrals (I'm just getting started with BTLE), but the typical pattern is for e.g. the heart rate sensor and smartwatch to both be peripherals of a smartphone. The first article you reference says: So for folks that may use one device for cycling and another for running, this could cause issues if both devices tried to connect to the heart rate strap at the same time. As long as you're not cycling and running at the same time, this isn't an issue.
swamp40 13y ago
So I don't really get why you'd want to use a $2.50 chip to half-ass implement the functionality of a $3 chip. (You can't bond, you can just advertise, and you can't do the necessary CRC.) The code's not that much different - just buy an nRF8001. Nordic started with the nRF24LE1 and tweaked the hardware to match the Bluetooth specs and turned it into an nRF8001. (Or better yet, use a TI CC2540/41. The documentation is much better.)

110 points by tdrnd 13y ago

This is awesome! The 2.4ghz nordic RF chip is cheap and easy to work with, I could imagine the guts of a simple "FitBit" style device made for just $5 at 'maker scale' of 1,000+ units. The ability to talk to android/ios phones cheaply will lead to some really cool projects. Obviously if you're going commercial you have so many other hurdles to cross that you may as well just use BTLE proper, but for hacking/making/prototyping it's very cool.

FigBug 13y ago
Why not just use a Nordic nRF51822 that comes with a full BLE stack, 32 arm processor, super low power. $2.50 per unit instead of using a separate micro and transceiver.
- acgourley 13y ago
  I guess because I didn't know those were that cheap - I'm out of date on this stuff and remember BT3.0 SoC's costing a lot more.
- krasin 13y ago
  In order to use BLE stack in nRF51822, one will need to deal with their DRM for the S110 SoftDevice, or implement an open source BLE stack similar to what the article suggests.
  - FigBug 13y ago
    What DRM is there? I thought the SoftDevice was just a binary blob? I'm currently in the prototyping phase of a product that uses the nRF5, I couldn't see any competitive advantage I would gain from developing my own stack considering the time investment it would take.
    - krasin 13y ago
      Have you noticed that you had to enter a serial number in order to get your SDK?
      - FigBug 13y ago
        Yes, is the Sdk somehow locked to the processor serial? How does production work?
        foolsday 13y ago
        The soft device is provided as a hex file and does not contain any DRM whatsoever.
        krasin 13y ago
        Can you post a download url to this hex file? Will the license allow you to do so?
        foolsday 13y ago
        The website requires a Product Key (not serial number) before it allows you to download the installer (I would assume for licensing reasons). The installer also includes documentation and tools that make working with the soft device easier.
        krasin 13y ago
        Thanks for the information. Yesterday, I have bought a few nRF51822, and will update this thread with my experience. While all early signs, including your words, indicate a good possibility that I will hit an unexpected problem due to the licensing scheme, the lack of the first hand experience does not let me be firm in my statements.

lnanek2 13y ago

> It has absolutely nothing to do with bluetooth besides the name Not really true. APIs on Android are mostly the same with a small new set of classes. HTC and Samsung and Broadcom have an API for over a year now and there's an Android standard one in the latest Android announced at Google IO. Enabling and pairing and device discovery are all the same from the Android side, though. Maybe an extra constant indicating the device type. Additionally, it's from the same group as Bluetooth, you often buy adapters and scanners and equipment and test software that are dual mode. This is why BLE is destroying older protocols for the same thing like ANT. ANT was never used much outside a few fitness and medical devices. BLE is all over the place since devices often have a Bluetooth chip in them anyway, so it isn't much more to make it dual mode. Many Android phones support BLE now. Also in that area, the big Bluetooth Unplugfest conference and testing event is there for BLE just like Bluetooth. So all the companies that go to get Bluetooth certified are there with the BLE offerings.

tadfisher 13y ago
Unfortunately, the Android BLE API only supports half of the standard, as Android devices cannot be placed in peripheral mode. This is something Apple released on day 1, and it's slightly infuriating when creating cross-platform applications. There is no good, non-hacky way to do local radio comms between iOS and Android, and it stinks. Here's hoping Kit Kat rolls out with full BLE support.
- JimDabell 13y ago
  > This is something Apple released on day 1 Actually, iOS had support for acting in central mode only in iOS 5 and added support for acting in peripheral mode in iOS 6.

locacorten 13y ago

Another cool hack with Bluetooth from MSR. Emulating a long-lived connection to a smartphone even when the phone is blocking incoming Bluetooth connections: http://research.microsoft.com/en-us/um/people/ssaroiu/publications/mobisys/2009/bluemonarch.pdf http://research.microsoft.com/en-us/um/people/ssaroiu/public...

thethimble 13y ago

Does anyone have any good resources for learning more about BLE?

Dwolb 13y ago
I haven't found comprehensive sources. Here's one blog that's good to reference when working with Bluegiga radios.
onebot 13y ago
This is the best resource on the subject, written by the designer of the protocol. The author is, surprisingly, a pretty good writer. This not only gives you everything you need to know (without grokking the spec), but also talks a lot about why they made the decisions they did. Highly recommend... http://www.amazon.com/Bluetooth-Low-Energy-Developers-ebook/dp/B009XDA1G8 http://www.amazon.com/Bluetooth-Low-Energy-Developers-ebook/...
- timthorn 13y ago
  He is also a very good speaker, if you ever get the chance to hear him.

nl 13y ago

Related, Samsung announced that they will be enabling ANT± on all their S4 phones, and apparently the S3 hardware can be enabled too(!) That's big news for anyone doing connected devices.

stbtrax 13y ago
It's good for legacy devices, but I can't think of any reason to use ANT in future products since you'd need to have a BLE version for iOS users.
- nl 13y ago
  Oh, because ANT+ lets you connect to multiple devices simultaneously. BTLE doesn't let you do that, and it's a pretty big problem. For example, if you do triathlons ANT+ lets you use a 910XT for the swim & run, and an Edge 500 for the ride without having to re-pair the devices. This isn't just a theoretical problem: according to a very recent DCRainmaker survey[1] 29% of people use this exact scenario[2]. iOS is bit issue of course, but there are ANT+ dongles and BTLE->ANT+ retransmitters (in the form of a heart rate monitor band). It's worth noting that the Stages power meter does do the dual BTLE and ANT+ transmission thing. I think ANT+ is going to hang around a lot longer than people think, especially in the field above casual fitness. [1] http://www.dcrainmaker.com/2013/09/curiositysurvey-different-cycling.html http://www.dcrainmaker.com/2013/09/curiositysurvey-different... [2] http://www.dcrainmaker.com/2013/10/symposium-keynote-presentation.html http://www.dcrainmaker.com/2013/10/symposium-keynote-present...
  - jmah 13y ago
    Bluetooth LE uses a client/server (called "central" / "peripheral") model; think of "server" like "web server", typically the client is your smartphone. I could believe that a single peripheral can't simultaneously connect to multiple centrals (I'm just getting started with BTLE), but the typical pattern is for e.g. the heart rate sensor and smartwatch to both be peripherals of a smartphone. The first article you reference says: So for folks that may use one device for cycling and another for running, this could cause issues if both devices tried to connect to the heart rate strap at the same time. As long as you're not cycling and running at the same time, this isn't an issue.

swamp40 13y ago

So I don't really get why you'd want to use a $2.50 chip to half-ass implement the functionality of a $3 chip. (You can't bond, you can just advertise, and you can't do the necessary CRC.) The code's not that much different - just buy an nRF8001. Nordic started with the nRF24LE1 and tweaked the hardware to match the Bluetooth specs and turned it into an nRF8001. (Or better yet, use a TI CC2540/41. The documentation is much better.)