CONNECT_REQ PDU can not receive

[zcmm]

hi,all i use use dongle as packet sniffer.when the phone can not connect my device,the dongle can not receive CONNECT_REQ PDU.if the phone can connect with my device,the dongle can receive CONNECT_REQ PDU; QS1:why can not receive CONNECT_REQ PDU when phone can not connect with device? QS2:the CONNECT_REQ PDU is from phone? QS3:when the phone connect with device,how long send CONNNECT_REQ PDU?

QS4:the 37 channel(2402MHZ) data is still not correct,and the rssi is weak(connect device is ok,and the device use DTM example,the 2402MHZ is 2402.168MHz by using the spectrometer ),but the 38 39 channel is correct,and rssi is normal. so i change the Crystals matching capacitance,from 30pf to 12pf,the 37 channel is correct. Why appear this kind of phenomenon?
QS5:i use the time_init create a timer(1s),and the lfclk is from NRF_CLOCK_LFCLKSRC_RC_250_PPM_TEMP_16000MS_CALIBRATION or NRF_CLOCK_LFCLKSRC_RC_250_PPM_250MS_CALIBRATION,the accuracy is very bad.Run 24 hours later, the timer error between 1-20 seconds(fast or low),Whether the internal crystals have a problem or firmware has a problem?

[Hung Bui]

Is there any chance that CONNECT_REQ PDU was never sent from the phone when the phone can't connect ? Then it's easy to understand why both the scanner and the device doesn't receive that packet.

How often do you see the phone can't connect ? Have you tried to increase the advertising interval to make it faster. The CONNECT_REQ PDU is sent when the phone receives the advertising packet.

[zcmm]

Different mobile phone is different.May be 50 times once.I have another question,pls see pictures

[endnode]

Is this your custom board? Have you verified all that with some proven HW like nRF52 DK?

[zcmm]

yes,it is my board.No,I have not test the DK,beacause i change my board Crystals matching capacitance from 30pf to 12pf,it is normal.This is very strange. Do you know QS5 ?

[endnode]

There is no reason why FW should cause malfunctioning on particular radio channel, this is all managed by the stack (Soft Device). I'm not HW engineer to advice on HW debugging but I guess that's pretty impossible to do over internet... If you have any doubts about FW then you should get some trusted HW (like DK or some 3rd party module) and verify it there.