SB20 - Can't Connect to Zwift

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If you use Zwift long enough, you have seen the following:









Since January, I've been writing a pair of iOS apps to monitor and control the SB20. While doing my testing, I saw the above behaviours just about every day. The reasons became fairly clear from my developer's perspective.

Why does my Bike Disappear from Zwift?

  1. The SB20 bike can have at most 2 Bluetooth connections. After this limit is exceeded, the bike is not visible to apps like Zwift.
  2. Each Stages power meter crank can have at most 2 Bluetooth connections. After this limit is exceeded, the PMs are not visible to apps like Zwift.
Sounds easy to manage, right? Not always. The hidden culprits are apps on your phone. It is common for an app controlling something like a TV or speaker, to connect to the SB20 and PM cranks to see what services they provide. To do this kind of "feature interrogation", one of the two available Bluetooth connections will be used. If the app developer is not careful, that connection can be maintained when you open another app. 

Here is an example of a feature I recently implemented:




This simple page lets you check battery levels of all nearby devices before starting a ride.  One click and you see all battery levels

I had to be careful to keep the related "discovery" connection times to a minimum since a user can move the app to the background (i.e., open another app) and keep its connections alive. 

If a connection is inadvertently maintained, the SB20 or power meter cranks can disappear from the Zwift Paired Device page.

FWIW: I used an array of timers to ensure no connection is held for more than 5 seconds 🤓









🔬ASIDE - For those who are technically inclined, Bluetooth connection problems are partially based on a misunderstanding between Zwift and Stages. The SB20 "advertises" that it is both a "fitness device" and "speed and cadence" device. Unlike most other bikes and trainers, the SB20 does not advertise that it is also a "cycling power" device.  Zwift occasionally gets confused particularly when the SB20 is already connected to other apps. 

What Can You Do?

If you are not seeing the SB20 or PM cranks in Zwift, try these steps:
  1. Turn your bike off/on
  2. Close and restart the Zwift app your phone, tablet or computer.
  3. Close the Stages Cycling app until your connect issues are resolved.
  4. Temporarily turn off Bluetooth on your phone until you are fully connected in Zwift.
  5. If you can't turn Bluetooth off  (if, for example, you using the phone to run Zwift), kill all apps on the phone that use Bluetooth until the problem is resolved. 
  6. If you have a Garmin computer configured to use Bluetooth, you should turn it off too.

Could the problem be the SB20 Bike?

Of course that's possible. Here my experience: For several months I connected, reconnected, sent bad data and had my iPad software crash countless times. The SB20 never failed to advertise its services and connect. The Stages bike may have issues with things like Erg mode, but its Bluetooth software (based on the Nordic/Ericsson Semiconductor wireless stack) is excellent. 

Does ANT+ have this Connection Limitation?

In short, the answer is no. There are few connection restrictions with ANT+. You can generally connect to as many devices as you wish.

Just be aware: ANT+ is typically available only on PC and Mac computers using a special USB dongle. Phone, iPads and Apple TVs are Bluetooth only. One bright spot are devices like Garmin computers.  They support both Bluetooth and ANT+. 

Want to learn more? Check out: Indoor Riding - ANT+ and Bluetooth 

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If you have an iPad and connect directly to the Stages Power meters, here's another connection issue that many people report: Stages SB20 - Zwift Connection Error 



Comments

  1. MarkApril 2, 2024 at 6:26 PM

    Thanks so much for this explanation. I'm new to the bike and to zwift, and have bern having frequent "connection failed" issues during rides, despite quick connection at first to my android tablet. Perhaps your suggestions will help.

    ReplyDelete
  2. Suzane73June 15, 2024 at 7:09 PM

    I was kindly referred to your blog by someone in the Zwift forums, as I am having difficulty with this very issue. Apologies for commenting here. My problem is slightly different in that both the StagesCycling app and Zwift cannot detect the bike. However, both apps see both power meters just fine. Do you have any suggestions I could try? I’ve tried unplugging, restarting, reinstalling, etc. Hoping it’s not an issue with the SB20 itself. Thank you!

    BTW, GearView looks great! If I can get things working again, it would be awesome to have everything on one screen.

    ReplyDelete

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