Anomaly 211 description

[KrystianL]

Hello,

could you advice me where can I find description of nRF5  anomaly 211 - the one described in nRF5 SDK 17.0.2?

Citation from 17.0.2 release notes:

...

- Added an optional workaround for anomaly 211.
If `NRFX_USBD_USE_WORKAROUND_FOR_ANOMALY_211 = 1` is set,
the USB stack will handle cases of waking up not preceeded by a resume signal.

...

Can not find it in errata to e.g. nRF52840:

https://infocenter.nordicsemi.com/topic/errata_nRF52840_Rev2/ERR/nRF52840/Rev2/latest/err_840.html

Br,

Krystian

[ovrebekk]

Hi Krystian

I will need to do some checking internally to figure out what information there is to share about this issue. 

I will try to get back to you in a couple of days. 

Best regards
Torbjørn

[ovrebekk]

Hi Krystian

Sorry for the slow response, it took some time to get to the bottom of this. 

Apparently this issue is caused by certain old USB hubs, which don't follow the USB specification properly when handling USB suspend. 

When the investigation was started this was treated as an anomaly, but since the problem was found to be on the hub side, and not on the nRF side, it doesn't count as an anomaly in the nRF device. This is the reason there is no mention of this in the errata. 

A workaround is in place to add tolerance for the behavior of these USB hubs, but applying the workaround will increase the sleep current significantly. This might not be a problem for a USB device, which typically has plenty of power available through the USB port, but to avoid increasing the current consumption for all USB applications the workaround has to be enabled specifically by setting this define. 

Best regards
Torbjørn

[KrystianL]

Hello,

thank you for exhaustive response.

[ovrebekk]

You welcome Krystian