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2 USB stick receivers and 16 bike speed sensors?

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Total Posts: 1

Joined 2010-02-19

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We are developing a Windows application that uses 2 ANT+ USB sticks as receivers and 16 bikes speed sensors (Bontrager).

For our initial development we used another computer with 2 ANT+ USB sticks. On this computer, we ran two instances of ANT Display Simulator v1.800 and configured each of the 8 channels in both apps to be bike speed sensors each with its own, unique Device ID. In our app on another computer (with 2 USB sticks) we paired the 16 simulated bikes speed sensors and everything works fine. We get some RX_FAILED messages, but that is expected.

When we pair with the actual Bontrager speed sensors instead of the simulated speed sensors, we get much different results. We do get some messages from the sensors, but mostly we get RX_FAILED events (expected) and *many* CHANNEL_COLLISION events.

So my understanding was that the ANT devices manage co-existence without me having to do anything. I'm not getting many (if any) collisions when I have simulated sensors. But I'm getting a lot of collisions when I use actual sensors. Am I dealing with a limitation on the Bontrager speed sensors? Or is it something in my code? Thanks.      
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Total Posts: 662

Joined 2012-10-09

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Please note that the performance you see when transmitting between two USB sticks sitting right next to each other is likely to be different than that of a set of sensors mounted on bikes and a USB stick. You may need to experiment with the positioning and orientation of the USB sticks on the receive end to improve your RF performance.

Channel collisions in your case are probably caused by dropping to search. As you are using 8 slave channels, make sure that you are only using low priority search to prevent search from preempting your active channels. Please refer to the following application notes for more details on channel collisions and search
AN15 Multi Channel Design Considerations
AN11 ANT Channel Search and Background Scanning Channel

Have you considered using Continuous Scanning Mode for this kind of application?
AN14 Continuous Scanning Mode for Asynchronous Topologies

You can find the application notes here
http://www.thisisant.com/pages/developer-zone/ant-application-notes      
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Total Posts: 1

Joined 2010-02-19

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Oh, man, I can't believe I didn't look into continuous scanning. It is perfect for our app. I did a quick test with the ANT Scanning Mode Demo and see that it can receive data from all 16 simulated bike speed sensors (and many more than 16 I suspect). I'll have to rework out app a bit, but it looks like continuous scanning will work for us.

I guess I didn't see this before because I was thinking that "continuous scanning" meant "continuous scanning for pairing". In other words, I was thinking that this was a pairing strategy.

Anyways, thanks a lot for your help!      
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Total Posts: 17

Joined 2011-01-24

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I'm having trouble getting the continuous scanning channel demo to work. When I try an ANT2 USB stick it just says Failed to Initialize ANT. And when I try an ANT1 stick it connects, but fails on the config.      
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Total Posts: 213

Joined 2011-05-02

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Thanks for bringing that to our attention. Someone will look into it as soon as possible.      
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Total Posts: 3

Joined 2013-12-19

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I don't know if it helps, but I am using Seego HR System with 1 USB, I think it is the m model (is the micro one).

The thing is we are only monitoring HR Belts (I get the other day 77 simultaneously. Picture attached)

The software has the option of combo sensor (speed+cadence), but I haven't try yet.

So, if I can have 77 users without problem simultaneously, I'm sure you will have 16!


     

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77.jpg

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