Gpio startup sequence for imx8qm apalis module

[AhmedMobarez]

Hello everyone,

I am using an apalis imx8qm module mounted on an Ixora board version 1.2.

right now when starting the ixora board the gpio pins (1-8) goes high for ~1.3 seconds then set to “low” as set up in pinmux.c , also the pins are connected to ground with a pull down resistor, my question is, is there any way to prevent this behavior and keep the pins grounded during startup ?

thank you

[josep.tx]

Hello @AhmedMobarez ,
You can try setting the GPIO values at boot time, as described in this thread:

iMX8X Setting default GPIO value in Device Tree

Hi @marcel.tx , I have same question too, do you have idea how to handle this ? Or you have any colleague good in device tree ?

Best regards,
Josep

[josep.tx]

Hello @AhmedMobarez ,
Do you have any updates on this topic?

Best regards,
Josep

[AhmedMobarez]

Hello @josep.tx ,

Thank you for following up, unfortunately I didn’t have time to test this issue, but I will test it early next week and let you know to close the thread, sorry for the delay.

but just to make sure, setting the pin levels in the device tree won’t conflict with controlling the pins from the firmware later?

Best,
Ahmed

[josep.tx]

Hello @AhmedMobarez ,

The title of the topic is misleading, it’s not about setting the pin levels in the device tree but setting them at boot time, in the U-Boot configuration.

By default GPIO pins configured as in input and you need to interact with a GPIO driver to set pin as an output and assign state. It can’t be done by Device Tee except this gpio-hog trick. From other hand you can select a pin pull-up or pull-down at Device Tree pin muxing section. Could it be enough for you case? Then when Linux boots you can set proper pin state by your app. You can also set pin state at U_boot level.

Please check the proposed solution, it might solve your issue.

Best regards,
Josep