OTA Failing when GPIO High Voltage Mode (3.3 V)

[Mattchew]

Hello,

We are working with the nRF52840 and the OTA works when I set 0x10001304 to a value from 0-3. When I set 0x10001304 to a value of 4 or 5, the OTA fails. 

[Vidar Berg]

Hello,

I can't think of any obvious explanations to this behavior, the internal operation on the chip should generally not become impacted by this regulator setting. Is there any external circuitry that requires a certain voltage range (e.g. external i2c sensor, etc)?

Some suggestion for further troubleshooting:

1. Check if the DFU target is advertising after disconnect. Maybe it's advertising with the wrong device name?

2. Attach a debugger to the board and see if the program is stuck somewhere. You can use "nrfjprog --readregs" to read the CPU registers from a running target.

[Mattchew]

It looks like our supply is 3.3V. If we change it to 3.6V input things work better. 

If we keep our input at 3.3V and change our output to 3.0V we still have the issue. Maybe we need to change the brownout level or one of the other thresholds?

infocenter.nordicsemi.com/index.jsp

[Vidar Berg]

The brown out threshold is not configurable, but it should not trigger unless VDD goes below 2.5 V. Could it be that the supply dips below this voltage level due to an increased load, or do you have a stable voltage supply? I think it may be worth trying to probe VDD with an oscilloscope to see if there are any voltage dips.