CC2640R2F: How to scan adv on a fixed channel

Mr Tian

Part Number: CC2640R2F
Other Parts Discussed in Thread: CC2640

Hello all,

Our application make use of adv package to perform localization task. According to our test, BLE adv on channel 38 is heavily influenced by other rf signals (lets say within setting period of time, channel 37 and 39 received around 100 packages, 38 only received around 60). So we want to scan on a fixed channel.

We understand it's aginst the BLE spec. However, we don't really need adv on other channle as we only use it to sense the strength of signal, instead of establish connection. Please kindly suggest what are the possible options. Many thanks!

over 3 years ago

0 YiKai Chen over 3 years ago

Guru 735535 points

You cannot fix scan channel. You can refer to similar discussions in this thread.

0 Mr Tian over 3 years ago in reply to YiKai Chen

Intellectual 700 points

Yi YiKai Chen,

Thanks for the reply. I notice there are some other threads discuss relatic topics and there's another thread claim that the restriction is mainly within the BLE stack, which TI needs to make the stack comply to BLE core spec...

One approach we are discussion is: if each scan is always start from ch 37, then we can make the scan_window/scan_interval/duration all equals to one value. After each scan duration, we manually trigger scan again. By doing so, if the assumption is correct, each scan duration will only have time to complete on ch 37, and will start again on ch 37...

Not sure whether this approach works... Besides, we are not sure if there's any better way to solve this.. Thats the reason asked.. Mnay thanks!

0 YiKai Chen over 3 years ago in reply to Mr Tian

Guru 735535 points

I don't think "scan_window/scan_interval/duration all equals to one value." is feasible to achieve this.

0 Mr Tian over 3 years ago in reply to YiKai Chen

Intellectual 700 points

Could you please kindly share your thoughts why this is not feasible? Device scan are not always start from ch37 on each GAPObserverRole_StartDiscovery call?

0 YiKai Chen over 3 years ago in reply to Mr Tian

Guru 735535 points

I don't see TI BLE stack allow developer to set such precise scan interval/duration.

0 Mr Tian over 3 years ago in reply to YiKai Chen

Intellectual 700 points

An example could be:

1) set window/interval/duration to around 2s, so it will scan on ch37 for 2s, before scan finish and GAP_DEVICE_DISCOVERY_EVENT event sent. adv can be received with GAP_DEVICE_INFO_EVENT within this 2s.

2) Once GAP_DEVICE_DISCOVERY_EVENT received, start another 2s device scan. Continue this process.

So by this approach, if assumption is correct, data might be lost between two scan session (as event schedule takes time, and during this process CC2640 is physically not scanning). Let's say we have 100ms blackout in every 2s. However, we receive 30% more adv package due to better channel performance. In this case, 100ms blackout in every 2s doesn't really matter...

0 YiKai Chen over 3 years ago in reply to Mr Tian

Guru 735535 points

I see you point now and sounds feasible to me now. You can try it to know if it works for your application.

0 Mr Tian over 3 years ago in reply to YiKai Chen

Intellectual 700 points

We've done a test and it proves proposed approach work. It continous scan on ch 37.

0 YiKai Chen over 3 years ago in reply to Mr Tian

Guru 735535 points

Cool and Thanks for sharing your results.

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CC2640R2F: How to scan adv on a fixed channel