Is it possible to continuously scan and while scanning connect to devices from time to time?

[yanshay]

I'm new to ble and trouble, developing on ESP32.
I want to continuously scan for devices. And to connect from time to time to some of them while scanning.
Preferably, do it from different tasks.
The Scanner takes ownership of central which is required for connecting. So is it possible to achieve with trouble or in general with ble?

[HaoboGu]

Sure, you can have multiple Centrals for scanning, connecting to peripherals, etc.

[lulf]

Try adjusting the scan window and interval. If they're too aggressive, the controller may not have time to satisfy the requirements of running them at the same time.

[yanshay]

What's considered agressive?
I tried from 100ms (window and interval, central is on power supply so not power issues), up to 10sec.
I can't say I feel any difference.
To discover and read two devices takes from 10 seconds to 30seconds (if more than that then it usually fail).
Is that reasonable?
The devices are Xiaomi Temp/Humidity sensors.

[HaoboGu]

According to my experience it's not normal. I tried with central + two peripherals, two peripherals connected within 5s.

[yanshay]

According to my experience it's not normal. I tried with central + two peripherals, two peripherals connected within 5s.

Is that including the scan or just the connect?
Is that including reading (so getting the service and then the characteristic and then reading the data - it is a three step process in my code}?

The pure connect from time it is initiated is about 2-3 seconds. But:

1. It takes about 10-15 seconds to discover the sensor, and they are found delayed. {and I'm using active scanning)
2. It takes another 2-3 seconds to get the service and charasteristic after the connection is made.

Does that sound reasonable?

Also, is there a way to skip to step of search for service/characteristic if I know the device including its address, service and characteristic in advance and cache some information from the first time I connect to it? To go directly to the read of the characteristic to speed things up?

[HaoboGu]

Including the scan. That's rough estimate though, I didn't test it