How to keep the pin's value
yyykkkyyy opened this issue · 5 comments
Hi, I really enjoy using this amazing gpio library !
BTW, when I use gpio_write function, it doesn't keep the value.
If I write 1 to the pin connected LED, the LED flashes for a moment.
Is this correct behavior ?
And can I keep the value without sleep() in C code ?
Thanks.
Hi @yyykkkyyy. It sounds like your program is terminating after the gpio_write()? If you are using character device GPIOs, e.g. with a /dev/gpiochipN device, you should keep in mind that the GPIOs won't retain their output state and will revert to a default state (likely an input) after being released when the program exits.
Thank you for your replying @vsergeev !!
Yeah, as you mentioned above, I use /dev/gpiochipN char device.
And I use the sample code which is on the README.
If you are using character device GPIOs, e.g. with a /dev/gpiochipN device, you should keep in mind that the GPIOs won't retain their output state and will revert to a default state (likely an input) after being released when the program exits.
Is this behavior the specification of /dev/gpiochipN?
Can I retain the GPIO's state ?
Yeah, that's the behavior of the Linux character device GPIO API. You can retain state after close with the sysfs GPIO API if you export the GPIO before c-periphery opens it (gpio_open_sysfs()), but the Linux sysfs GPIO API is deprecated and will be removed in future versions of Linux.
Oh, Okay. I understood the behavior !
In fact, I used the sysfs GPIO but I knew it will be deprecated. So I explore the other way.
Thank you very much @vsergeev !!!
And sorry for my poor English :-)
No worries. Feel free to open an issue if you have any other questions or problems.