How to receive data constantly with single channel

[GyuHyeon Lee]

• Nrf51822
• SDK : nrf51_12.2.0
• soft device : s130
• Example : ble_app_beacon

I’d tried single channel adverting with nrf51 beacon.  And I referenced this way to disable other channels.

https://devzone.nordicsemi.com/f/nordic-q-a/11401/advertising-on-a-single-channel-with-s132

Finally, I got the conclusion grape1, grape2. Admittedly, using only 37channel is more stable than using multi channel. But, here is the question. 

Why is there no receive beacon data on single channel periodically?

[Edvin]

I have not heard that using only channel 37 is more stable than using all 3 channels. In my opinion I would say it is the opposite, because if you are in an environment with a lot of noise on channel 37, you can still rely on the other two channels, 38 and 39.

 

However, I believe that the reason for why you are seeing the gaps in the graph is because the scanner is scanning on all 3 channels. However, the scanning timeslots and advertising timeslots are a bit different. Advertising is advertising on all 3 channels in a burst, and then goes to sleep until the next advertising event. A scanner will  scan on 1 channel for a given period of time (scan window), then change channel and scan there for the next scan window, and so on. Hence, when the scanner is scanning on channel 38 or 39, it will not hear the advertisements on channel 37. In Graph2, you don't have the gaps because when you are scanning on channel 38 and 39, you will still hear the advertisements from the peripheral, because it is using all the channels.

 

To summarize, it is not more reliable to only use one channel to advertise. Rather the opposite.

A scanner can only scan on one channel at the time.

 

Please see this post on advertisements for a more thorough explanation.

 

Best regards,

Edvin