[199] USBD: USBD cannot receive tasks during DMA

nRF52840 Revision 3 Errata

This anomaly applies to Revision 3, build codes QIAA-Fx0, CKAA-Fx0.

It was inherited from the previous SoC revision Revision 2.

Symptoms

The USBD does not perform incoming tasks.

Conditions

The USBD is performing a DMA transfer.

Consequences

If any EasyDMA transfer is in progress, USB tasks cannot be used.

Workaround

To enable incoming tasks when using DMA, use the following code when starting a DMA transfer: 

*(volatile uint32_t *)0x40027C1C = 0x00000082;
After the DMA transfer is completed, use: 

*(volatile uint32_t *)0x40027C1C = 0x00000000;