Can the nRF52840 do USB power class negotiation?

[Richard Gledhill]

Hi everyone,

We are investigating whether the nRF52840 can be used to carry out USB device negotiation with a host in terms of setting the maximum charging current.

Our potential device doesn't actually need USB data support, so until now we've just connected the USB power and ground to the charger chip, which is a "dumb" charger, i.e. not a USB-specific charging chip.

If we connect the USB lines to the micro, can it do the necessary negotiation and/or configuration of D+/D- lines to enable higher charging currents from a USB host?

I realise an alternative is to use an off-the-shelf USB device/charger chip, but these are expensive and board space is limited.

Thanks

Richard

[Øyvind]

Hello Richard, 

Please see this answer from my colleague Stian. The USBD is USB 2.0 compliant but does not have built-in support for the Battery Charging Specification rev 1.1.

Kind regards,
Øyvind

[Richard Gledhill]

Hello Øyvind,

Thanks for the link.  Is it physically possible to implement BCS1.1 using the nRF52840 ? In other words can we implement BCS1.1 in software and, if so, what hardware changes might be required on our board on the D+/D- connections?

Kind regards,

Richard

[Øyvind]

Hi Richard, 

I'm sorry but I don't have an answer to that. I have forwarded your question to our HW team and will respond as soon as I have an answer. Do note that we are moving into vacation time here, and some delay must be expected.

Thank you!

Kind regards,
Øyvind

[Richard Gledhill]

Thanks, that's great!

[Øyvind]

Hi Richard, thanks for your patience. 

The answer from the HW team is:

Implementing BC1.1 support on the nRF52840 without any external HW is not possible. The options then would be to purchase an off-the shelf charger detection part, or design/implement something similar to what these off-the shelf parts do. Is the detection of all charger types required? Or is DCP detection sufficient? If only DCP detection is required, it could probably be done using an external GPIO analog-"switcher" with some additional GPIO usage on the 840, and 2 resistors.

I hope this answers your question. 

Kind regards,
Øyvind

[Richard Gledhill]

Hi Øyvind,

Thanks for the detailed answer.  In this case we'll look at using an off-the-shelf part.

Kind regards,

Richard