Not able to set the GPIO low permanently from the command line

[darla14]

Hello,

I am using STM32mp157f-dk2 board and I have a peripheral connected on GPIO pin #16 ( PF1)

on doing gpoiget gpiochip5 1 > i get 1

on doing gpiosetgpiochip5 1=0 i DO NOT get any error but on doing again gpioget gpiochip5 1 > i get 1 again

I see it is shared with SDMMC3_CMD . On directly connecting it to Ground , it becomes low , not otherwise from the above commands.

Is this the same MMC on which starter image is written?Is it safe to pull it down permanently from the hardware?

  

May I know how to make it low from the software permanenetly.

Regards,D

[PatrickF]

Hi @darla14​ ,

may I suggest to try using devmem2 to directly access GPIO registers.

e.g.

# enable GPIOF IP clock in RCC
devmem2 0x50000A28 W 0x00000020
 
# set PF1 in GPIO output mode
# read the value (I read 0xBFBFFFCF on my DK2)
devmem2 0x50007000 W 
# write the value modified with MODER1=0b01
devmem2 0x50007000 W 0xBFBFFFC7
 
# set PF1 = 0 using bit BR1 in GPIOF_BSRR (but PF1 should be already 0 as default value)
devmem2 0x50007018 W 0x00020000

Regards.

[PatrickF]

In fact, using "gpioget gpiochip5 1" will put PF1 in input mode (I assume you have an external pull-up as you read '1'), so should not be used after having issued "gpioset gpiochip5 1=0" which put PF1 in output with '0'.

Regards.

[darla14]

Thanks @PatrickF​  This worked actually by following example code on stm32mpu wiki using the libgpiod example code :

Regards,

[PatrickF]

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