For anyone developing apps for Mac, an update is required to use USBm and USB2 ANT sticks for the new change introduced by the El Capitan OSX release.
We have identified the root cause as a change to the low-level USB communication behavior that causes the ANT USB communication pipes to stall and stop sending and receiving data. El Capitan changed the behaviour negotiating with the USB device during initialization so it is possible now for the USB pipe flags to become out of sync. From the app perspective, the app will stop receiving messages and any of the command message functions that wait for a response will fail. From the user perspective, it often appears as if the ANT stick is not present unless they unplug and replug the stick.
We have identified a software solution to avoid the problem, and will release a new version of the ANT library soon. The solution is to pump the USB pipe with messages in a specific order to get the communication flags in the right state. The new version will also have several other stability improvements and error fixes for OSX.
Solutions:
* Switch your app to use the new version of the ANT library when it becomes available
* If you can't wait for the new library, please refer to the patch at
http://pastebin.com/abjxvtEV to make the changes in your current library version yourself.
* If you are not building the library yourself you can try a similar workaround in your own code to request the capabilities message twice and wait for the response as soon as you connect to the ANT stick. Wait for the response for each request, but ignore failures. Then proceed with the rest of your ANT operation as normal.
* If you are a consumer arriving here browsing the Internet for a solution, please contact the developers of your app and refer them to this post. Additionally, you may find success using an app that is fixed already such as Garmin Express to open the ANT device first, then close Express and use your desired app.
If you have any questions or comments please respond below.
