i.MX8 M USB1 OTG - how to change polarity of OTG_PWR/OC?

[mehrenfried]

We followed your DOC-346008 implementation guide for OTG port without Type C connector. But we did not recognized the fact that USB1_OTG_PWR and USB1_OTG_OC are high active.

We validate that i.MX8 M recognize the USB1_OTG_OC as active high, even if the DOC-346008 claims the signals as low active signal.

The USB1_ID pin resistor R210 is marked as DNP in DOC-346008. Without the connection between the connector ID pin and USB1_ID (R210 assembled), i.MX8 M does not react on ID pin changes.

Is it possible to change the polarity of i.MX8 M USB1_OTG_PWR and USB1_OTG_OC from high active to low active?

Please confirm that the connection between USB1_ID, USB1_OTG_ID and microUSB ID pin is mandatory.

Regards,

Matthias

[weidong_sun]

Hi Matthias，

1. USB1_OTG_OC's logic

It is overcurrent pin, if the current that USB provides for external device is more than 500mA, FLAGA & FLAGB will ouput LOW , then USB1_OTG_OC will be pulled down to LOW.  Then software should drives USB1_OTG1_PWR pin to disable U28's OUTPUT ( OUTA or OUTB)

so this is the meaning of "Active Low "

2. USB1_ID or USB1_OTG_ID

Here USB1_OTG_ID(GPIO ID) should be used.  Because some customers use it successfully.

Hope above information is helpful to you!

Have a nice day!
B.R,

Weidong

[mehrenfried]

Hi Weidong,

it is understood that the FLAGA &FLAGB drives the signal low, if an overcurrent is detected.

But from a datasheet perspective, USB1_OTG_PWR and USB1_OTG_OC are defined as high active signals.

There is no low active flag like USB1_OTG_OC# or USB1_OTG_OC_N.

Are you allowed to confirm, that the iMX8M ALT1 USB1_OTG_OC pin is a low active, and the datasheet is not correct?

But I have to admit that if we configure the GPIO as ALT1/USB function pins, the Linux boot log reports an OVERCURRENT Condition, when the USB1_OTG_OC signal is high (no physical overcurrent condition)

It seems, other customers implements the pin as low active and changed the polarity or remove the ALT1 function and use the pin as a GPIO.

This is why I’m asking so persistent. Your statements and my observations do not fit. And before we start a redesign to change the polarity of the signals externally, I want to be sure that we understand the issue completely.

Regards,

Matthias

[weidong_sun]

Dear Matthias,

     Could you tell the following situation on your board?

1. USB1 works in device mode

When USB1 works in device mode, is it normal to download the image to the eMMC/SD card on the board?

2. USB1 works in Host mode

When USB1 works in host mode, can VBUS Pin on USB connector provide 5V power to external USB devices?

Thanks!

Have a nice day!

Weidong