I am using X1 Pin 5 (GPIO3) to control a BJT, with the goal being that the GPIO pin will be low during power-up / boot. According to section 4.4 in the Apalis iMX8 datasheet, this pin default to an input with pull-down resistor. Additionally, I have a 20k external pulldown. Even so, during power-up and boot, this signal goes just high enough to turn on the BJT, which indicates that it is somehow being pulled up in the iMX8. It remains in this state until we take control of the pin and set it to an output.
I am also using X1 Pin 7 (GPIO4) in a similar way, and it is behaving the same way.
Is there a mistake in the datasheet regarding the PD default state indicated? I can work around this problem by changing the value of my 20k external pulldown, but I need to understand why and how the pin is being pulled up so that I can properly select the value of the external pulldown. Thanks!
Hi @PGB74,
In case it makes a difference, could you state what version/release of software you are using when you experience this?
Best Regards,
Jeremias
There is no external pull ups on mentioned pins. And they should be in Hi-Z mode after power on. Could you stop boot at U_boot stage by pressing “space” at terminal connected to debug UART and check pins status?