ANT Forum

Hi all, I have been doing a bit of investigation regards adding wireless capability to our existing product. We got underwater data loggers and main datalogger unit and our customer is interested to be able to link up the underwater data loggers with the main datalogger.

One thing that attract us was Ant low power consuption, but the system is as follow:

*There could be multiple data loggers that need to link up to the main datalogger (one master, multiple slaves)

*The main logger will initialize went it wants to do a download of all loggers (doesnt matter if one at a time).

*The underwater dataloggers radio link needs to be low power due to system constrains, but they need to be on the lookout for the master signal went to begin data transfer.

*Needs to be bi-directional communication.

*The main logger doesnt know how many underwater loggers are in the network, hence it needs to do a search mode.

*I understand there 8 channels on the drop-module (AP2 Module)
How could i utilize it efficiently.

Sorry for all the questions, I am new to wireless protocols so any guiding help would be very appretiated

Thank you in advances
Chris      

Do the underwater loggers need to transfer data while underwater? ANT uses a 2.4GHz radio, for which water is a pretty big challenge.

As long as the data transfers can be performed outside of the water, there are several ways you could achieve the topology you describe; which one is the most efficient depends a lot on your power and latency requirements. Since the underwater loggers are the more power constrained portion of the system, you may benefit by configuring them as masters and setup the main logger as the slave, with independent channels for each of the underwater loggers. You may also want to consider background scanning channel or the continuous scanning mode for the main logger unit.

To get more familiarity with ANT and figure out whether it is suitable for your project, we would recommend having a look a the "ANT Message Protocol and Usage" document. The first sections will provide a description on how ANT channels work, and what does it mean to be the master or slave.
http://www.thisisant.com/pages/developer-zone/ant-protocol-and-usage

Application Notes AN11 ANT Channel Search and Background Scanning Channel and AN14 Continuous Scanning Mode for Asynchronous Topologies would also provide you some idea on how you could make the topology you want.
http://www.thisisant.com/pages/developer-zone/ant-application-notes      

Thanks alejandra for responding

Firstly no, the underwater loggers do not need to do data transfer underwater, the conditions of the data transfer is once a day (went all the underwater loggers being retrieve) and went the main data logger station request each logger to send the data invidiually.

The limitation might be the main data logger station(mainly ram to buffer recieve data to be store into external dataflash) so invidiual underwater logger download might be the way to go.

We not overly worry about data transfer speed, as long it doesnt take hours ( there might be up to 8 underwater loggers with worst case scenario of 40,000 bytes to be send).

I hope this is a bit more info.
Thanks heaps
Chris      

Since you will be sending larger chunks of data, ANT-FS may fit your needs. Sequential individual downloads, configuring the main unit as the host and the underwater loggers as client devices would fit your use case. You can find more information about ANT-FS here (registration required)

http://www.thisisant.com/pages/ant/ant-fs-specification

Getting a hold of a devkit and exploring the capabilities of ANT and ANT-FS using the PC tools (ANTware, ANT-FS PC host and PC client)would be quite helpful for your evaluation.