with nrf52840 how to detect (scan/sniff) a beacon, identify UUID and aftet go to sleep for one second

RE: with nrf52840 how to detect (scan/sniff) a beacon, identify UUID and aftet go to sleep for one second

Simonr — Fri, 15 Nov 2019 07:41:45 GMT

Thank you for the clarification! Okay, so a beacon transmitting every 1 second, should mean that scanning for 3 seconds at a time will be sufficient for detecting at an advertisement each scanning interval. So, setting the scan duration to 3 seconds should be sufficient there. Then, when you're done, tell the device to go to system idle mode for 2 seconds or so. The attached file just need to set the time you're asleep for to 2 seconds. You can do this by using the RTC. Enable RTC with something a function similar to this.

void rtc_enable(void)
{
	nrf_drv_rtc_counter_clear(&rtc);
    nrf_drv_rtc_tick_enable(&rtc,true);
	mcuInSleep = true;
}

Attached is a main.c file that should work as a beacon scanner going to sleep after the scan duration is over, so you just have to implement the RTC to sleep for the desired amount of time.

devzone.nordicsemi.com/.../main.c

Best regards,

Simon

RE: with nrf52840 how to detect (scan/sniff) a beacon, identify UUID and aftet go to sleep for one second

yahdar72 — Thu, 14 Nov 2019 10:39:06 GMT

Hi Simon,

I work for a company that ask to me to make firmware for a beacon detector (beacon already created and is capable to send advertise every 1 second consuming only 3uA ) in few work days; in the menawhile I also must follow other activities with greater priorities, so as you can image I can devote few time to understand libraries and BSP.

The beacon, for power saving, send an advertise every 1 second.

With one seconds beacon transmission, in my mind with the scanner that listen for 3 seconds, the scanner should be able to detect the beacon in every situation, also after a long sleep. Is this right?

If 3 second are too few, by your expirience, how many seconds the scanner need as a minimun to detect beacon?

I hope these informations are useful and you can help me.

Best regards
Yahdar

RE: with nrf52840 how to detect (scan/sniff) a beacon, identify UUID and aftet go to sleep for one second

Simonr — Thu, 14 Nov 2019 09:21:26 GMT

And what exactly are you struggling with? Are you able to scan and detect the beacon? If the device only is scanning for 3 seconds before going to sleep, There won't be a guarantee that it will be able to detect the device every time. What's the advertising interval of the beacon?

Best regards,

Simon

RE: with nrf52840 how to detect (scan/sniff) a beacon, identify UUID and aftet go to sleep for one second

yahdar72 — Wed, 13 Nov 2019 20:43:03 GMT

sorry for my bad english, I'm working on a central (scanner) and pratically I need only to detect an external beacon with a specific UUID that my central knows. when the beacon with UUID is near to the scannel, that is when signal level (RSSI) is over a value, I must set an output pin (I/O) at high level. When beacon is far and signal level (RSSI) under a value, or not detectable (lost), then that output pin must set low.

The work is simple, but there is also another small problem, the system must go in sleep (under 2uA), or wake up, by the level of another I/O (an input pin). When nrf52 is active (Input pin externally kept high) the detect state must continue for 3 seconds and after has to go sleep for 2 seconds, and so on until input pin will be pulled low.

Best regards,

yahdar

RE: with nrf52840 how to detect (scan/sniff) a beacon, identify UUID and aftet go to sleep for one second

Simonr — Wed, 13 Nov 2019 13:50:06 GMT

Sorry, but what do you mean by "intercepting" a beacon detection? Can you please try to explain a bit more about what you want to do, and what you're struggling with? Are you working on a central (scanner) or a peripheral (beacon)?

Best regards,

Simon

RE: with nrf52840 how to detect (scan/sniff) a beacon, identify UUID and aftet go to sleep for one second

yahdar72 — Wed, 13 Nov 2019 09:24:13 GMT

Hi simonr

thanks for the very usefull reply, but looking for a place/function where intercept beacon detection, I have meets some problem because I don't understood how to detect a specific becaon (scanning filter?) and where detect this event to move a I/O.

Please could you be so kind to give me some indications?

thanks in advance and best regards

RE: with nrf52840 how to detect (scan/sniff) a beacon, identify UUID and aftet go to sleep for one second

Simonr — Thu, 07 Nov 2019 09:18:15 GMT

Sorry for the delayed reply. You can check out our ble_app_blinky_c example, where you can edit the SCAN_DURATION define yourself. Note that the duration of the scanning is stated in units of 10ms, and if it's set to 0x0000, scanning continues until it is explicitly disabled.

Best regards,

Simon

RE: with nrf52840 how to detect (scan/sniff) a beacon, identify UUID and aftet go to sleep for one second

yahdar72 — Tue, 05 Nov 2019 20:39:59 GMT

First of all, thank for the answer ketiljo.

I'm newbie with nrf5 and BLE so if is possible to have some link to an example code for a central that start and stop scanning for a predetermined time will be very usefull for me.

RE: with nrf52840 how to detect (scan/sniff) a beacon, identify UUID and aftet go to sleep for one second

ketiljo — Tue, 05 Nov 2019 13:31:58 GMT

Not sure what you are trying to do here. In order to scan for a beacon, you need to jeep the central in scanning mode for as long as it takes to detect the beacon. It doesn't wake up and start scanning by itself. You need to define how often you are scanning and for how long.