RE: Message synchronization with no connection

Sigurd — Mon, 21 Jan 2019 16:01:45 GMT

Hi,

The scan request/response mechanism is not really designed for message synchronization in mind. Also note that all active scanners will generally request the scan response packet. So both sensor and network node need to know each other’s BLE address, to filter out other scanners. And you will need to add the network-node BLE address in the sensor whitelist, so that only the network-node will trigger the sensor to send a scan_response.

1) No. The SoftDevice will send the application the BLE events asynchronous, and also note that the real advertising interval is adv_interval + advDelay, where advDelay is a pseudo-random value with a range of 0 ms to 10 ms generated by the Link Layer for each advertising event. So you should just enable the scanner with a given scan interval and window, and wait for the network node to send the configuration ADV packet, and the sensor to receive it. If you have not received it within a couple of seconds, you could turn the scanner off and restart the procedure.

2) The SoftDevice handles this for you. The 3 advertising channels(37,38,39) will be used.

3) It could work, but it will depend on your implementation on how robust it will be. I think it would be a lot more robust to connect to the sensor devices. The network node could keep a list of all senors, and when it wants to configure them, it could iteratively connect to the sensors and configure them. If you have alot of sensor devices, it could also be worth checking out Bluetooth Mesh for this type of sensor network.