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GPIO pins high during Pre-loader/Uboot 5CSE-H4-3YA
Added by Brian Wentworth about 8 years ago
Hello,
I have a project where I hooked up leds to several gpio lines. The gpio lines go high for about 5 seconds (which is not acceptable for this application) during what seems to be the preloader/uboot stage and then go low once the countdown "hit any key to autoboot completes" is displayed in the user terminal. Is there a way to specify the logic level on those pins on initial power up?? ie. modify a file or configuration setting in preloader/uboot..
As always, thanks for the support
Brian
Replies (3)
RE: GPIO pins high during Pre-loader/Uboot 5CSE-H4-3YA - Added by Daniel Vincelette about 8 years ago
Hi Brian,
Unluckily the initial values of the GPIOs aren't configurable from what I've seen. You could edit board/cl/mitysom-5csx/mitysom-5csx.c and in the board_init function set the GPIOs values but I'm not sure how long it takes to get that point after power on.
Another idea we have is set those pins an LOAN IO, so they are controllable from the FPGA. This should set them as floating on power up but you'd need to put a PIO core in the FPGA in order to control them. Also some of the GPIOs are used for BSEL/CSEL on powerup so they're initial state would need to be taken into consideration too.
Dan
RE: GPIO pins high during Pre-loader/Uboot 5CSE-H4-3YA - Added by Brian Wentworth almost 8 years ago
Dan,
Thanks for the reply. I am able to better control them using an external weak pull down circuit on power up, which gives a determinate state (Low) during boot.
Thanks again for the great ideas.
Brian
RE: GPIO pins high during Pre-loader/Uboot 5CSE-H4-3YA - Added by Daniel Vincelette almost 8 years ago
Brian,
Glad to hear that worked!
Dan
