MX25R64 cannot enter DPD.

Question

Hello, 
 We found that the nrf52840 cannot properly pull the CS pin high to get the MX25R64 into DPD. The SDK version is nrf connect SDK V2.0.0. The macro CONFIG_PM_DEVICE=y has been enabled. At this time, the driver nrf_qspi_nor.c should be able to control the MX25R64 to enter the DPD. But when we measured the CS pin level, it was always low. How to pull the cs pin high in nrf_qspi_nor.c ? 
 Thanks.

helsing · Answer

Hi Bon, here is the pull request with a fix for the missing pull-up on the CSN line: https://github.com/zephyrproject-rtos/zephyr/pull/48645 "When there is no external pull-up on the CSN line and the line is put into the low-power mode (input direction and disconnected buffer), after some time its level falls to low and some flash chips, like for example MX25R64, exit the Deep Power-down mode when that happens. To prevent this, activate the GPIO internal pull-up for this line in boards that do not have the external pull-up on it. "