Page 1 of 1
Reading output GPIO pin logic state
Posted: Mon May 21, 2018 4:06 pm
by x-8973
I needed to know the logical level on the pin, which is set to output. The gpio_get_level() function always returns 0, even after a gpio_set_level(GPIO_PIN, 1). Is there any way to find out the logical level on such a pin?
Code example:
Code: Select all
gpio_config_t io_conf;
io_conf.intr_type = GPIO_INTR_DISABLE;
io_conf.mode = GPIO_MODE_OUTPUT;
io_conf.pin_bit_mask = (1 << GPIO_OUTPUT_IO_LED);
io_conf.pull_down_en = GPIO_PULLDOWN_DISABLE;
io_conf.pull_up_en = GPIO_PULLUP_DISABLE;
gpio_config(&io_conf);
while (1)
{
if (gpio_get_level(GPIO_OUTPUT_IO_LED)) // If pin is switched on
{
ESP_LOGI(__func__, "LED on");
gpio_set_level(GPIO_OUTPUT_IO_LED, 0); // Switch pin off
}
else
{
ESP_LOGI(__func__, "LED off");
gpio_set_level(GPIO_OUTPUT_IO_LED, 1); // Switch pin on
}
}
Re: Reading output GPIO pin logic state
Posted: Mon May 21, 2018 6:31 pm
by loboris
The question was asked several times already, you must set the gpio mode to GPIO_MODE_INPUT_OUTPUT (or GPIO_MODE_INPUT_OUTPUT_OD) if you want to use the gpio as output and read its state back. Or you can simply save the state in a variable after gpio_set_level().
Re: Reading output GPIO pin logic state
Posted: Mon May 21, 2018 7:24 pm
by x-8973
I did a search on the forum, but did not find anything suitable. Thank you, now I will know)
Re: Reading output GPIO pin logic state
Posted: Thu Feb 14, 2019 4:07 pm
by flodis
If you are interested in the last output state of a pin you can read from either GPIO_OUT_REG (31..0) or GPIO_OUT1_REG (32..39).
To detect if port is input or output you can read the GPIO_ENABLE_REG (31..0) or GPIO_ENABLE1_REG(32..39)
If you are sure the direction is not changed outside your control a non atomic direct port access for pin 0..31 like this may work:
Code: Select all
gpio_num_t pin = (gpio_num_t)(your_pin_number_0to31 & 0x1F);
int state=0;
if (GPIO_REG_READ(GPIO_ENABLE_REG) & BIT(pin)){
//pin is output - read the GPIO_OUT_REG register
state = (GPIO_REG_READ(GPIO_OUT_REG) >> pin) & 1U;
}
else
{
//pin is input - read the GPIO_IN_REG register
state = (GPIO_REG_READ(GPIO_IN_REG) >> pin) & 1U;
}
Details here:
https://github.com/espressif/esp-idf/bl ... gpio_reg.h
https://docs.espressif.com/projects/esp ... /gpio.html
https://www.espressif.com/sites/default ... #section.4
Re: Reading output GPIO pin logic state
Posted: Tue Aug 10, 2021 5:17 am
by JL1946
Many thanks to @flodis for your code snippet. It worked for me...
I implement a timer to toggle the Blue Led on a Esp32 Dev Board...
My Code is as follows:
Code: Select all
#define BLINK_GPIO 2
void blink_blue_led() {
gpio_num_t pin = (gpio_num_t)(BLINK_GPIO & 0x1F);
int state = 0;
if (GPIO_REG_READ(GPIO_ENABLE_REG) & BIT(pin))
{
state = (GPIO_REG_READ(GPIO_OUT_REG) >> pin) & 1U;
if (state == 0) {
gpio_set_level(BLINK_GPIO, 1);
} else {
gpio_set_level(BLINK_GPIO, 0);
}
}
}
Re: Reading output GPIO pin logic state
Posted: Tue Sep 07, 2021 11:26 pm
by ayham24
Hey Could you please somehow send me your whole package of the program if it's ok? cuz i'm trying since days to do it but i don't know what's wrong here
i would be really thankful
Re: Reading output GPIO pin logic state
Posted: Sat Oct 22, 2022 3:19 am
by davidhbrown
flodis wrote: ↑Thu Feb 14, 2019 4:07 pm
... read from either GPIO_OUT_REG (31..0)
or GPIO_OUT1_REG (32..39)....
Emphasis added as I'd missed that on first reading and it turned out I was using GPIOs 32 and 33 (hidden behind #defined constants so I'd forgotten)
Thank you for the example; it's working great.
Re: Reading output GPIO pin logic state
Posted: Thu Jun 13, 2024 11:44 am
by bojanj
I'm trying to compile pieces of the code posted here with the latest Arduino (IDF 5.x). WHich libraries do I have to #include?