Using nRF52840 to send data over open sea surface

[Harry94]

I am currently working on a project where I try to send data from a swimmer in the open sea to a point on the land (beach). I know that Bluetooth communications are blocked by the water, but would it be possible to achieve this communication whenever the wrist of the swimmer (wearable) is out of the sea? Will the sea environment allow this communication?

[Harry94]

Hi Edvin, 

Thanks a lot for your reply. 

What if only wanted to establish the connection (just for detection purposes)? What could I use if I wanted to achieve fast connection? 

Best regards, 

Harry 

[Edvin]

On peripheral (typically the device with the smallest battery, so I assume the wristband thing), you need a short advertising interval. On the Central (the scanning device), you need a large scan window (preferably equal to the scan window). Depending on what acts as your central, you may or may not be allowed to use the radio 100% for scanning. If it is a mobile phone, you will not, but if it is another nRF, just set the scan window = scan interval. 

Then, on both devices, set your preferred connection interval to be as low as possible. Again, if the central is a phone, you can't decide exactly what it is going to be. If it is an nRF, set both minimum and maximum connection interval to be 7.5ms.

What you would want to do then is to keep track of your connected and disconnected events. That is, the BLE_GAP_EVT_CONNECTED, and BLE_GAP_EVT_DISCONNECTED.

I don't know exactly how the position in the water will affect the range. You would have to do some testing to figure this out.

So what is your central in this connection? Is it a phone, or do you intend to use nRFs as both peripheral and central in the connection?

Best regards,

Edvin