ANT Forum

Hello,

In our asynchronous application, we use the continuous scanning mode and it consumes significant power. It would be nice to start and stop this continuous mode so that performance during scanning is not affected and all Ant+ devices are found. This may save us some power.

Unfortunately, I see no command in S210/S310 stacks to stop it. There are couple of time out parameters that can be set, but not sure if it is doing a time-out on continuous/background scanning. Is there any documentation specific to achieving this?

Any information is greatly appreciated.

Thank you!
     

Hi,

Search time out parameters do not apply for Continuous Scanning mode. To stop continuous scanning mode you must call the sd_ant_channel_close() method (nRF51 SDK) with Channel 0 as the parameter.

You may use the search time out parameters (in addition to the close command) if you are using a Background Scanning Channel. The two available methods in the nRF51 SDK:

sd_ant_channel_low_priority_rx_search_timeout_set()
sd_ant_channel_rx_search_timeout_set()

It is recommended that the Background Scanning Channel is operated in low priority search mode, even though it looks like you will only be using one channel.

You can find more information in the following documents:

AN 14 Continuous Scanning Mode
AN 11 Channel Search and Background Scanning Channel

Available on our downloads page: http://www.thisisant.com/developer/resources/downloads/#documents_tab


     

Thank you for the helpful answers!

In terms of radio usage, is background scanning channel intermittently used as opposed to full-blown continuous mode? Is there any difference in SNR values of these two channels?

Reason for having a background scanning channel, is it more for interference assessment?

It would be nice to have time outs on Continuous scanning mode in the future releases of nrf51 SDK.
     

You are susceptible to missed packets using the Background Scanning Channel (See waveform in Channel Search and Background Scanning App Note) whereas in Continuous Scanning mode the radio is continuously active and you should receive all transmitted packets. (As long as they are in range and without RF interference).

Using a background scanning channel allows you to have other ANT channels open on the device and uses less power compared to continuous scanning mode. Most ANT+ master devices transmit at ~4Hz, and worst case scenario with a background scanning channel it will take ~3 seconds to find an ANT+ device (although the average acquisition time would be ~1s). Using continuous scanning mode the device will receive all packets, so listening for ANT+ devices transmitting at ~4Hz you can expect acquisition times of <1s.

You can always implement time outs for the Continuous Scanning Mode using the timers available on the nRF51.