nRF52840 using Zephyr 2.0.0
We currently have a system that after we are running can drop to 20uA. However, on boot, we draw something like 5-7mA. This large on boot current draw is causing the nRF to enter brownout condition because we are running off a coin cell and the internal resistance of the coin cell is 150 ohms when capacity is depleted some. This is bricking the device because it drops to brownout but not low enough to trigger BOR. I have solved this in hardware so i can reboot the nRF at brownout conditions.
when I reboot though, the nRF52840 pulls so much power that it just causes it to go into brown out again. so i am in a constant BOR loop.
I noticed on boot, for 350ms we dont seem to have a problem, so what is being ran in this time period?
After the 350ms, this is where the large current draw appears, pulling the VCC rail down. After the 350ms, what is happening?
Is the 350ms, loading of the Zephyr OS, and then after that we run our code? If so, what can we do on boot to reduce current draw to less than 1mA on startup? We even tried running firmware where we just pout a while loop in main and it still boots with 5-7mA before dropping to a little less than 1mA. Is there any low current minimal boot examples out there to reference?
We do need to be able to have only BLE operating at this point in time, as it is a low power beacon-type mode only when on coin cell.
