i2c on USB_H

[jeroenvanderlaa]

Hi There,

we're having a prototype based on an MCIMX6X1EVK10AB. We're experiencing some problems with i2c4 that we connected on USB_H_DATA & USB_H_STROBE. There are multiple issue here where I would like to have some information about.

We measure an voltage of 1.95V coming out of NVCC_USB_H (pin V5). In my understanding this is an input and the voltage is used for the pads USB_H_DATA & USB_H_STROBE (pins Y5&W5) even if configured for i2c use. As implied by this post: i.MX6SX GPIO voltage select (USB_H_STROBE) 

If I look at 35.5.375 and 35.5.376 from IMX6SXRM it describes operations at 3.3V which is higher then the maximum voltage of the mentioned post (table10 of IMX6SXCEC).

We would like to use i2c4 on USB_H with a level of 3.3V is this possible? We can except voltage levels of 1.8V but prefer 2.5V if 3.3V is not possible.

What is the proper way to connect and configure our board?

Should we apply a voltage on NVCC_USB_H can we configure this element?

What should be the proper configuration of the pads in a dts file for Linux?

Best regards,

Jeroen van der Laan

[igorpadykov · Accepted solution]

Hi Jeroen

NVCC_USB_H max. allowable voltage is 2.75V according to

Table 10. Operating Ranges i.MX6SX Datasheet, it can not be set to higher values.
https://www.nxp.com/docs/en/data-sheet/IMX6SXCEC.pdf

From software side there are no dts changes compared with 3.3V option.

In general one can use solutions provided on web,  like AN10441 Level

shifting techniques in I2C-bus design

https://www.nxp.com/docs/en/application-note/AN10441.pdf 

Best regards
igor
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[jeroenvanderlaa]

Hi Igor,

thanks for confirming those questions. But as is the problem with a multi question post a few questions remain unanswered. Glad that you answered these questions.

Is it possible to configure NVCC_USB_H that it actually suplies a voltage (like 1.95V) or is always an input?

Best regards,

Jeroen van der Laan

[igorpadykov]

Hi Jeroen

NVCC_USB_H is always an input.

Best regards
igor