ANT Forum

Hello,

we are working on an ANT network solution and we use the background scan to keep in contact with all network nodes. However, the background scan does not search permanently (as shown in figure 1 of the attachment). Our network nodes are mains power supplied. So, we don't have a battery lifetime problem.

Is there a way to improve the search quality of the background scan if power is no issue (as shown in figure 2 of the attachment)?

Best regards
Berthold [file name=Background_Search.pdf size=487519]http://www.thisisant.com/images/fbfiles/files/Background_Search.pdf[/file]      

I am not sure what your specific need is, but you might consider using the "Continuous Scanning Mode" feature. When an ANT channel is put into this state, it dedicates 100% of the radio to searching, and therefore will always find every single message that in range. The downsides of this are power draw (not an issue for you) and that no other channels can be active while scanning is enabled. It depends on your application, but you could possibly use continuous scanning at certain times and background search at other times. Look at Application Note 14 for more information:

http://www.thisisant.com/pages/developer-zone/ant-application-notes

If this is not suitable, one thing you can try on your background scanning channel would be to disable low priority search, and use high priority search only, which may result in slightly better search performance.      

Hy jefferson,

thanks for your reply. The "Continuous Scanning Mode" feature is very interesting, but not exactly what I need. I am using 1 master, 1 background scanning channel and slave channels to connect temporarily to ANT devices. Every network node sends network messages over the master channel to other network nodes and receives messages from other network nodes using the background scan. Since the number of network nodes in range is not defined, this is the only possible solution.

It is a pity that the "Continuous Scanning Mode" works with the highest priority and only allows one channel. A continuous scanning mode which can be interrupted by any other channels would be what I am searching for.

Thanks for your help      

If your application is custom (not ANT+) one additional option would be to play with channel periods in your design and try to find an increased level that still allowed all of your channels to operate. A rough guide of channel period to search time is as follows:

Transmission ---------- Worst case search time
10 Hz ----------------- 2 seconds
4 Hz ------------------ 3 seconds
2 Hz ------------------ 7 seconds
1 Hz ------------------ 15 seconds
0.5 Hz ---------------- 45 seconds

If you are on ANT+, then unfortunately, there isn't much else that you can do in this situation.      

yes I read this too, but unfortunately I also want to bring bursts through the network. I believe when I have many network nodes close to each other with a permanent master channel, then increasing the message period of all master channels will also increase the chance to interfere with the bursts.
Thanks to you Jefferson, I am already thinking about increasing the message period only for very important messages and reduce them afterwards. Since I have no slaves connected to the master this should be an acceptable compromise.
In case that someone has other ideas, how to improve the background search, please let me know.
Thanks,
Berthold      

I know you said you wanted to use bursts, but if you can settle for just using broadcasts and adjusting the rate, you can use the continuous scanning mode in RX-only mode (stops it interfering with bursts - also means it can't transmit/receive bursts) on channel 0, with up to 7 pseudo-channels for transmitting broadcast data to other masters on their time slot(you can of course use channel 0 to transmit to anyone, but I think you can only queue a single message at a time if you do that).

This way you don't miss any data except for in the case of collisions.

I was looking for a way to do what I think you were wanting too; have a continuous background RX-only channel and 7 normal channels, but it's not possible.      

Hello doug,

for my application I need at least 1 master for sending permanent broadcasts to the other nodes and a background scanning channel. In continues scanning mode it is not possible to have a master and only answering on a message from a master is possible. However, when every node is in continues scanning mode, then there is no master to answer.

If there is a way to send a broadcast message periodically while staying in continues scanning mode, then that would work for me fine. Because then I can turn the continues scanning mode off to use normal slaves if necessary and switch it on afterwards. But I haven't found anything in ANT_AN14 (application node 14), so I believe that this doesn't work neither.

Regards,
Berthold