i.MX283 USB data lines Hi-Z

[thrtn]

We are an OEM with a project that uses the i.MX283. Instead of using the
on-board charger, we are using an external charger that can provide more
current to charge our batteries. The charger does D+/- negotiation and
requires a processor that can place the D+/- lines in a HI-Z state for 1
second following power. Is it possible to place the USB_0 D+/- lines in this
state?

[igorpadykov]

Hi Tr

according to p.6 attached AN4199 app note:

"i.MX28 processor can be programmed to distinguish between the USB and wall-power

sources by sensing the status of the D+/D- USB signals", this could be done using

procedures given in "Battery Charging Specification Revision 1.0" from usb.org.

So if used external charger is compliant to this specification i.MX28 can support it.

Best regards
igor
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[thrtn]

I think you have misunderstood what I'm asking. For this particular project, the charger we are using does its own D+/- detection. It cannot rely on the D+/- detection done by the i.MX28, therefore programming the i.MX28 to make the distinction is not helpful. For the charger to complete the detection properly, it needs to be attached to a processor whose D+/- lines are in a Hi-Z state for the first second after power is applied. Is it possible to place the i.MX28's D+/- lines in a Hi-Z state?

[igorpadykov]

> Is it possible to place the i.MX28's D+/- lines in a Hi-Z state?

no. Only supported functionality as described in "Battery Charging Specification Revision 1.0" from usb.org.

Best regards
igor