If I understand correctly, the default advertising type set by Adafruit is: BLE_GAP_ADV_TYPE_CONNECTABLE_SCANNABLE_UNDIRECTED
Within an advertising interval, the peripheral will first transmit on ch37 and switch to receive mode to listen for any scan/connect request; it then will repeat the same again on ch38 and ch39.
If we do not need the packet to be scannable/connectable, we should be able to set the type to:
BLE_GAP_ADV_TYPE_NONCONNECTABLE_NONSCANNABLE_UNDIRECTED
I suppose the peripheral’s radio will only transmit on ch37, 38, 39 and will not enter receive mode. Not sure if this can further lower the power consumption. I do not have the tools with me to verify the idea but at least the code compiles and the packet can be received by the central.
Bluefruit.Advertising.setType(BLE_GAP_ADV_TYPE_NONCONNECTABLE_NONSCANNABLE_UNDIRECTED);
Bluefruit.Advertising.restartOnDisconnect(true);
Bluefruit.Advertising.setIntervalMS(100, 100); // in unit of ms
Bluefruit.Advertising.setFastTimeout(5); // number of seconds in fast mode
Bluefruit.Advertising.start(5);