Device not booting up after SystemOff (NRF52840)

RE: Device not booting up after SystemOff (NRF52840)

AGeegee — Wed, 08 Jul 2026 12:54:45 GMT

Yes the steps are correct.

1. Disable IRQs

2. Setup GPIO

3. SYSTEMOFF

I would like to understand the situation where the lockup can occur, because it can cause our device to never turn back on.

As a test inserted a SPI EasyDMA Tx between 2 & 3, and it doesn't make the lockup any easier to reproduce.

RE: Device not booting up after SystemOff (NRF52840)

Kenneth — Wed, 08 Jul 2026 12:40:53 GMT

Hello,

So just so I don't misunderstand the flow, you are doing:

1. __disable_irq is made. ISB and DMB for good measure too

2. the GPIOs are setup for DETECT on LATCH

3. Go to System OFF

Right? I just want to ensure you have not swapped step 1 and 2.

[quote user="AGeegee"]If there are on going EasyDMA transactions, what would happen?[/quote]

Slightly undefined. Usually higher power consumption and partial transfer, but it may I guess also cause lockup.

Kenneth

RE: Device not booting up after SystemOff (NRF52840)

AGeegee — Wed, 08 Jul 2026 11:43:23 GMT

Thanks for the quick reply.

Before entering SYSTEMOFF a call to __disable_irq is made. ISB and DMB for good measure too. Before the System goes off all interrupts are disabled and the GPIOs are setup for DETECT on LATCH.

If there are on going EasyDMA transactions, what would happen?

RE: Device not booting up after SystemOff (NRF52840)

Kenneth — Wed, 08 Jul 2026 11:38:07 GMT

Hello,

Not directly related to the problem, but there is a note in the datasheet that: "Before entering System OFF mode, all on-going EasyDMA transactions need to have completed."

So in general we do recommend that you have a safe/proper disabling everything before going to system off. But in this case I suspect that there may be some higher level interrupts occurring shortly before you want to go to system OFF, and indirectly reconfigure or change "something" that prevent wakeup from system OFF to work. So you might also at some point shortly before you go to system OFF disable all interrupts before you configure the hardware exactly as you want before going to system OFF.

Kenneth