nRF52840 USB EventReady Hang

[George Beckstien]

I am trying to implement the HAL interface for USB devices in Mbed for the nRF52840. Mbed is currently on nRF SDK14.2 so I may not have all the most recent bug fixes for the USB driver.

I am following the example in examples/peripheral/usbd and am enabling and starting the USBD peripheral using the POWER events. I am encountering an issue where calling nrf_drv_usbd_enable() hangs while waiting for the USBD READY event (see the following lines:https://github.com/AGlass0fMilk/mbed-os/blob/f2df72078397c8305cd57c36046237f7186ce704/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_14_2/drivers_nrf/usbd/nrf_drv_usbd.c#L1706-L1710)

I am also seeing a hardfault on startup if USB is plugged in when I reset the MCU.

You can view my implementation here:

github.com/.../USBPhy_Nordic.cpp

Any insight into why I might be seeing this behavior?

[Kenneth]

I suspect this issue: http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52840.Rev1.errata/dita/errata/nRF52840/Rev1/latest/anomaly_840_187.html?cp=2_0_1_0_1_20 

[George Beckstien]

Alright, so I have taken the extra code from the SDK V15.2 version that includes the workarounds for Errata 171 and 187 and now it gets past the enable. Thanks for that.