sometimes my board cannot be reset

[DonWoo]

hi,I got a very strange phenomenon when our board begin a mass production.Here is some details:

1.Our board use a 4.2v lithium battery;and we have downloaded our firmware in 300 piece chips.

2.Then we found 30 boards which cannot reset by nrfgo studio with JLINK(SWD).

3.Disconnect the lithium battery then connect again,it can be reset.

4.The same problem happened sometimes when long press the main key.This key can make the power management chip generate a reset signal on SWDIO pin when be long pressed.And the SWDIO pin just connects to the power management chip.ALSO in this situation we found a pulse waveform in SWDIO pin in oscilloscope when long press.

What can i do to locate this problem?Cause our production is upcoming. Many thanks in advance.

[Hung Bui]

Hi DonWoo,

This issue happens only once (you power reset it and it never happens again) or it some times occurs again ?

Note that right after programming, the device will retain in debugging mode and the reset pin won't able to reset the chip.