Reading Fast Changing Input from Input Pin

RE: Reading Fast Changing Input from Input Pin

Håkon Alseth — Thu, 26 Mar 2020 15:05:58 GMT

Hi,

No worries. Glad to hear that you found the root cause!

Kind regards,

Håkon

RE: Reading Fast Changing Input from Input Pin

kb2423 — Thu, 26 Mar 2020 15:04:53 GMT

Sorry, it was my bad. Pin should be no pull up/down, I didnt know this. Before nrf I was working with stm32 it could handle the data when pin was pull down, so I thought it must be pull down. But I was wrong, thank you for answers.

RE: Reading Fast Changing Input from Input Pin

Håkon Alseth — Thu, 26 Mar 2020 11:43:00 GMT

Hi,

Isolate the problem and test the specific pin.

Start with a very small example, like blinky, and just read the input, and if it changes, increment a variable / toggle a LED or something (change to the GPIOs in question):

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/** @file
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 * @defgroup blinky_example_main main.c
 * @{
 * @ingroup blinky_example
 * @brief Blinky Example Application main file.
 *
 * This file contains the source code for a sample application to blink LEDs.
 *
 */

#include <stdbool.h>
#include <stdint.h>
#include "nrf_delay.h"
#include "boards.h"
#include "nrf_gpio.h"

/**
 * @brief Function for application main entry.
 */
int main(void)
{
    /* Configure board. */
    bsp_board_init(BSP_INIT_LEDS);
    nrf_gpio_cfg_input(BUTTON_1, NRF_GPIO_PIN_PULLUP);
    /* Toggle LEDs. */
    while (true)
    {
        uint32_t pin_state = nrf_gpio_pin_read(BUTTON_1);
        /* Pin is active low */
        if (pin_state == 0) {
            static uint32_t active_count;
            active_count++;
            /* Visual aid */ 
            nrf_gpio_pin_toggle(LED_1);
        } else {
            /* Pin inactive - do nothing */
        }
    }
}

/**
 *@}
 **/

Does this run? If yes, then there's no hardware problem (soldering or otherwise). It does not work? Then check your connections.

Kind regards,

Håkon

RE: Reading Fast Changing Input from Input Pin

kb2423 — Wed, 25 Mar 2020 19:17:36 GMT

I dont have oscilloscope so I dont know how is signal. I listened other device with stm, and configure some of stm pins to copy those signals then I made connections between nrf and stm. When that device sends signal stm sends same signal to nrf, now I can read the data thanks to stm board. Whats the problem and how can I fix it?

RE: Reading Fast Changing Input from Input Pin

Håkon Alseth — Wed, 25 Mar 2020 12:24:35 GMT

If that pin is solely used as an input, there should be no restrictions, and it should work as a normal input pin. Have you scoped the signal to see if there's anything strange with the voltage or wave form going into the GPIO?

Kind regards,

Håkon

RE: Reading Fast Changing Input from Input Pin

kb2423 — Wed, 25 Mar 2020 11:56:11 GMT

That device doesnt use SPI or UART, they have their own communication protocol, a pin as a clock and a pin as a data.

I am checking P0.23 and configured it with this nrf_gpio_cfg_input(23,NRF_GPIO_PIN_PULLDOWN); . As I said before I use same pin with same configuration as a button it gives me one and zeros. But it cant detect ones that coming from other device. That device's period is 9 us for 1 bit.

RE: Reading Fast Changing Input from Input Pin

Håkon Alseth — Wed, 25 Mar 2020 07:52:48 GMT

[quote user=""]But when I connect it to other device for communication it can not detect changes. [/quote]

Do you mean that you connect it as a GPIO input, then as a SPI MOSI pin for instance (or UART or any other peripheral)? If that is the case, the peripheral will claim the selected GPIO. You cannot use a GPIO as input in addition to a UART TXD simultaneously.

[quote user=""]My nrf52832 is always giving me 0. How can I fix that?[/quote]

Regardless of which GPIO you're checking, you're always getting 0? Have you configured the respective gpio as input? You can do that by calling nrf_gpio_cfg_input().

Kind regards,

Håkon