What might cause a HardFault on sd_app_evt_wait()?

[Eliot Stock]

I'm ending up in the HardFault_Handler() on calling sd_app_evt_wait() within a function that reads from the UART. What might cause that? Stack screenshot attached.

I have the SoftDevice enabled at the time but am not advertising (although I'd like to be advertising at the same time at some point, incidentally). The problem's not reliably reproducible, but it happens fairly often.

[Ole Morten]

Normally, my best guess would be that you do this from interrupt priority higher than the SVC interrupt priority, in other words higher than 2. As described in the architecture chapter of the Reference Manual, this is not possible, and will cause a HardFault directly. However, your back trace seems to indicate that you come from main, in which case this sounds strange.

Are you sure there isn't something about your memory setup that's not correct? Are you able to reproduce the problem when running with command line GDB? If so, can you please share an example project?

[Ole Morten]

It doesn't matter which interrupt priority you configure your UART with, as long as you're not calling the softdevice version from a function running with this priority. I'd be happy to take a look at your code, both regarding this and the other problem you've posted, so please post a support case and include as much as you can.