i.MX6 Boot Cfg

[davidwende]

Many of the boot_cfg (LCD) pins are muxed to interfaces such as I2C or SPI.

How does the pullup / pulldown on the config pin exist in harmony with for example always pullup on I2C signals?

[davidwende]

Hello Igor and thanks for your response.

It is still not entirely clear.

In my case (using MCIMX6Y2DVK09AB) I have a I2C port multiplexed with 2 of these configuration pins.

Now I2C requires pullups to VDD, value depending on I2C speed and line capacitance, but lets says around 3-10k.

If the required boot cfg value is high, then all OK.

However if the required value is low, then the 10k resistor to ground will be installed, but there will still be a pullup to VDD through the series combination of the  isolation resistor and the I2C pullup.

I would appreciate if you could consider this case also.

David

[igorpadykov]

Hi David

in such case one can use more complex isolation circuit used in i.MX6SL EVK spf-27452 p.13

Schematics (2)
Design files, including hardware schematics, Gerbers, and OrCAD files. (REV 1)
http://www.nxp.com/products/microcontrollers-and-processors/arm-processors/i.mx-applications-process...

Best regards
igor

[davidwende]

Thanks Igor,

That is a good help.

David

[igorpadykov]

Hi David

if boot pins are used for other purposes isolation circuit should be

used, 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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