ENC (encoder) setting phase inputs with pullup on rt1050?

[jackking]

I am trying to use inputs GPIO_B0_12 and GPIO_B0_13 as phase inputs to the ENC peripheral.

In the SDK samples the phase pins have pull-down set, but I am trying to use an encoder with common to GND, so I need pull-up enabled.  In the PIN CONFIG tool I have set pull-up for those pins, and I also tried using an external 10k pull-up resistor, but regardless it seems those pins have pull-down enabled.

Even just scoping the pin directly and using GPIO, I don't see the input pulled up...  On other pins I have successfully set pull-up, but GPIO_B0 pins seem to all be pulled down.

Here is my pin setup:

Any help appreciated!

[igorpadykov · Accepted solution]

Hi Jack

you are right, in general if GPIO_B0 pins should be used later for other purposes one can use

isolation circuit described in sect.2.3 Bus isolation circuit i.MX6 System Development User’s Guide

https://www.nxp.com/docs/en/user-guide/IMX6DQ6SDLHDG.pdf

Best regards
igor
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[jackking]

Well, a lot of the GPIO_B0 pins are used at boot time for BOOT_CFG, so they have external 10k pull-downs (on the EVK). 

So it doesn't look like you can use B0 as pull-up inputs while the fuses aren't set.