SCAN_REQ length and Online Power profiler values

[EmmaJaf]

Hi all,

As we will al agree refering to the BLE standard, a SCAN_REQ Frame contains 176 bits (22bytes), and since the BLE legacy standard datarate is 1Mbit/s, the duration of a SCAN request is 176us.

We you have a look at the online power profiler and set it for Advertising TX/RX mode, as below, we see that the 3 RX windows, which should receive the SCAN_REQ sent over the 3 standard advertising channels, are of length 60us.

My question is: where do I miss something ? 

[EmmaJaf]

Would this mean that the RX window is only searching for the preamble and if detects something would go on listening to obtain the whole packet?

[Stian Røed Hafskjold]

Hi,

EmmaJaf said:

Would this mean that the RX window is only searching for the preamble and if detects something would go on listening to obtain the whole packet?

Correct.

The online power profiler does not include SCAN_REQ (and scan response). This would have been misleading in terms of power consumption, since under normal conditions only a few of the RX windows actually receive a scan request. So, the radio turns on the receiver for about 60 us, and if no preamble has been received, the receiver is turned off again.