Automation Control Services for Quasi Real Time applications using BLE 5

[jinvers]

Dear Sirs,

I am evaluating the option of controlling a couple of motors (each with an independent controller based on a nRF52840 device) from a Smartphone App. Both controllers receive the same orders  from the smartphone and both motors should actuate near simultaneously. A first idea is using indications to Include acknowledge messages from each nRF52840 device, just to be sure of a right RF link between the smartphone and the two nRF52840. I understand that it's not possible to have a full synchronization between both motors and I think the full mechanical set would accept a maximum delay of 60ms-70ms between the time response of the two motors. 

Do you finf this application could be succesful? What kind of GATT service would you suggest to use or take as a example to be adapted?

Thank you very much in advance.

Best Regards,

Joel Invers

[Karl Ylvisaker]

Hello Joel Invers,

I understand that it's not possible to have a full synchronization between both motors and I think the full mechanical set would accept a maximum delay of 60ms-70ms between the time response of the two motors. 

Do you finf this application could be succesful?

As with all radio communication it is impossible to guarantee that a packet will reach the other device successfully, since there might be obstacles or noise in the environment which prevents this. This is thus highly dependent on the positioning of the two devices relative to each other, and the environment in which they are operating in. Could you elaborate more on both these aspects in your application?

In general, I can say that the lowest possible connection interval is 7.5 ms for a BLE connection, and any packets that are not acknowledged will be retransmitted in the following connection event. Longer packets have a higher probability of being corrupted by noise in the environment, and I do not know anything about the command length in your case.
If your tolerance is 60 ms, and the devices have a reasonable placement and operating environment, I would think that this should work fine with BLE.
Your description of the use case is however pretty sparse, which makes it hard to say anything with a larger degree of certainty. Could you elaborate further on your use case?

Best regards,
Karl