I have a custom design PCBA that mimics the beacon reference design (exact same circuit). For reference, I am running from a primary lithium cell and bucking. However, I am using AT25XE011 as my external flash. The FW I am running is your DA14580_BEACON_3.40.6-> dialog_beacon_fh. The beacon does function, can boot from flash (and SmartSnippets can connect and erase/write/read external flash thru JTAG), and advertises.

However, I am experiencing an unexpected current flow and battery sag through the memory ic, which ultimately leads to a very short battery life and run time. I have isolated this down to the CS pin. When I attach an AT25XE011 to the WLCSP breakout board from the pro-kit, I get the exact same behavior. Looking at the CS pin with a scope, it does not stay high after the initial memory read on bootup, which I would expect (de-selected when not in use, pulled up or pushed up internal to the DA14580). I can add a pullup (used a 10k in testing) from the CS line to the battery power rail which removes the battery sag. However, the CS pin isn't pulled all the way to the battery rail (I'm seeing a ~0.75V differential with a battery voltage at ~2.9V), so there is current flow across the resistor and/or through the memory IC.

Can you provide any insight into the source of the problem? Are there GPIO settings for the CS pin that need to be adjusted? Does the AT25XE011 behave differently than the W25X10CL?

Thanks,
John