Two BLE devices send data to each other

[JohnCC]

Hi,

   We are evaluating a pedal power meter for bicycle, but have a question we would like some advice.

Usually pedal-type power meters are divided into left and right sides. The right pedal transmits the pedaling data to the left pedal through BLE protocol and then the left pedal transmits the data to the mobile phone uniformly.

If we want to complete the right pedal transmitting data to the left pedal. What kind of BLE protocol should we use? Is there an example for reference?

Thank you.

John.

  

[Amanda Hsieh]

Hi,

Due to the Easter holidays in Norway, we are less staffed than usual. You can expect an answer sometime next week,

Sorry for the inconvenience and thanks for your patience. 

Regards, 
Amanda

[Karl Ylvisaker]

Hello John,

Usually pedal-type power meters are divided into left and right sides. The right pedal transmits the pedaling data to the left pedal through BLE protocol and then the left pedal transmits the data to the mobile phone uniformly.

If we want to complete the right pedal transmitting data to the left pedal. What kind of BLE protocol should we use? Is there an example for reference?

You say that it is 'usually' being sent to the left pedal then bundled and re-sent - is this topology the ideal one you would like to go with in your project, or could it also be an option to send it directly to the receiving device, without going through the left pedal? The main drawbacks of sending it through the left pedal will be that it increases the power consumption of the left pedal compared to the right one (so the left will be out of charge faster than the right one), and it introduces additional latency - it could of course be that neither of these are issues in your use-case/design, I just thought I should mention them just in case.

In either case, you can use a regular BLE connection to send the data from the right pedal (either to the left pedal, or directly to the intended receiver).
You could for instance start out with the NUS service example from the SDK to give this a try.

If you are not already familiar with the nRF Connect SDK I highly recommend going through the nRF Connect SDK Fundementals course at the DevAcademy to quickly familiarize with it! :) 

Best regards,
Karl