GPIO control during BOOT

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ltbleakney@gmail.com
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GPIO control during BOOT

Unread post by ltbleakney@gmail.com » Fri Jan 18, 2019 2:00 am

I have an ODROID C0 that I am using to control some large hardware, I would like to have some of the GPIO driven low during boot. I am using Ubuntu Mate and my program is taking advantage of WiringPi (written in C). I have seen a post about this with the XU4 but I don't know where the config files for the C0 that need to be edited are. Also I think that person was ok with tristate/high impedance and I need to drive them low.

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Re: GPIO control during BOOT

Unread post by odroid » Fri Jan 18, 2019 11:35 am

Which GPIOs pin do you want to change?

Refer the S805 datasheet as this thread to know the initial state.
viewtopic.php?f=111&t=30496

ltbleakney@gmail.com
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Re: GPIO control during BOOT

Unread post by ltbleakney@gmail.com » Wed Jan 23, 2019 2:02 am

My problem is probably more about how I do anything durring boot, I can find the memory address for each of the 7 pins I want low durring boot. I just don't know how to have any of my code run before the software which is set to run on boot. the flow chart on page 37 of the boot process could help me if I wanted to do a little assembly (or find a compiler?) programming to run before I start the normal boot loader, but that seems like a ton of work, and I feel like there aught to be something easier.

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Re: GPIO control during BOOT

Unread post by odroid » Wed Jan 23, 2019 11:29 am

If 7 pins are input mode by default, simply add pull-down resistors.

Otherwise, you might need to change the u-boot(boot loader) source code and compile it with GCC on your Linux PC.
https://wiki.odroid.com/odroid-c1/softw ... ing_u-boot

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