Hello,
We have a custom NRF52840 board that can be powered via both Battery and USB. The peripherals that are connected to the board require it to be in high power mode supplying 3.3v.
We have noticed that during development, if we do not have the battery plugged in and USB connected, the board will fail to flash via the J-link on the nrf52840DK almost every time. The custom board is powered via VDDH through a charge controller. The measured voltage on this line is 3.7v without a battery which to my understanding should be more than enough to flash the board. With a battery I get a reading of 3.8v.
Am I missing something? I cannot understand why a board would be unflashable despite having necessary voltage. There is a line running to Pin P0.30 from the charge controller that will be used to read the charge state of the battery. The charge controller states the signal is tai-state. Is that something that could cause the chip not to flash?
We had a previous board that did not suffer from this problem, the only difference between that there was no connection to Pin P0.30.
Thanks in advance.
Griffin
