GPIO Control

JN GPIO Port

The Jetson GPIO signals are routed through a bidirectional level shifter before reaching the external GPIO connector. The level shifter translates between the Jetson's 1.8V I/O domain and the connector-side 3.3V domain.

Connector Pin	Signal	Jetson SODIMM Pin	GPIO Identifier	Sysfs #
1	VDD_5V_SYS	—	Power	—
2	GPIO00	87	GPIO3_PCC.04	228
3	GPIO01	118	GPIO3_PS.05	149
4	GPIO02	124	GPIO3_PH.06	62
5	GPIO03	126	GPIO3_PI.02	66
6	GPIO05	128	GPIO3_PH.07	63
7	GPIO07	206	GPIO3_PV.00	168
8	GPIO10	212	GPIO3_PV.01	169
9	GPIO11	216	GPIO3_PZ.00	200
10	GND	—	—	—

Level Shifter

GPIO pins on this connector operate at 3.3V. Do not apply 5V directly to any GPIO pin.

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What is sysfs?

Linux exposes hardware interfaces under /sys using a special virtual filesystem called sysfs. GPIO, PWM, I2C, SPI and other hardware components appear as simple files inside this structure.

Info

This allows GPIO pins to be controlled using simple file writes: export → direction → value.

Terminal Code Example

This example demonstrates how to set GPIO with sysfs ID 228 (GPIO00) to HIGH and LOW using the terminal.

echo 228 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio228/direction
echo 1 > /sys/class/gpio/gpio228/value
echo 0 > /sys/class/gpio/gpio228/value

How to Calculate the Sysfs Value from a GPIO Name?

• Download the pinmux configuration file for your specific Jetson module. It is available on NVIDIA's official documentation page.
• Inside the downloaded pinmux_config_template.xlsm file, you will find two sheets:
  • The first sheet contains general notes and explanations.
  • The second sheet (jetson_[xx]_module) lists the GPIO names along with their detailed identifiers (e.g., GPIO3_PI.01).

• In an identifier such as GPIO3_PI.01:
  • The letters (e.g., PI, where I is important) correspond to the TEGRA_GPIO_PORT value.
  • The number after the dot (01) represents the pin offset.
• The Sysfs GPIO number is computed using the following formula: TEGRA_GPIO = (TEGRA_GPIO_PORT * 8) + pin_offset
  • You can find this formula in the tegra194-gpio.h header file.

tegra194-gpio.h

#define TEGRA_GPIO(port, offset) \ ((TEGRA_GPIO_PORT_##port * 8) + offset)
#define TEGRA_GPIO_PORT_A   0
#define TEGRA_GPIO_PORT_B   1
#define TEGRA_GPIO_PORT_C   2
#define TEGRA_GPIO_PORT_D   3
#define TEGRA_GPIO_PORT_E   4
#define TEGRA_GPIO_PORT_F   5
#define TEGRA_GPIO_PORT_G   6
#define TEGRA_GPIO_PORT_H   7
#define TEGRA_GPIO_PORT_I   8
#define TEGRA_GPIO_PORT_J   9
#define TEGRA_GPIO_PORT_K  10
#define TEGRA_GPIO_PORT_L  11
#define TEGRA_GPIO_PORT_M  12
#define TEGRA_GPIO_PORT_N  13
#define TEGRA_GPIO_PORT_O  14
#define TEGRA_GPIO_PORT_P  15
#define TEGRA_GPIO_PORT_Q  16
#define TEGRA_GPIO_PORT_R  17
#define TEGRA_GPIO_PORT_S  18
#define TEGRA_GPIO_PORT_T  19
#define TEGRA_GPIO_PORT_U  20
#define TEGRA_GPIO_PORT_V  21
#define TEGRA_GPIO_PORT_W  22
#define TEGRA_GPIO_PORT_X  23
#define TEGRA_GPIO_PORT_Y  24
#define TEGRA_GPIO_PORT_Z  25
#define TEGRA_GPIO_PORT_AA 26
#define TEGRA_GPIO_PORT_BB 27
#define TEGRA_GPIO_PORT_CC 28
#define TEGRA_GPIO_PORT_DD 29
#define TEGRA_GPIO_PORT_EE 30
#define TEGRA_GPIO_PORT_FF 31

• After substituting the port index and the pin offset into the formula, you obtain the corresponding sysfs GPIO number.

Example

GPIO00 sysfs value is 228
GPIO00 -> GPIO3_PCC.04
TEGRA_GPIO_PORT = CC
Offset = 4
TEGRA_GPIO = (TEGRA_GPIO_PORT_CC * 8) + 4 -> (28 * 8) + 4 = 228

Warning

This Formula Does NOT Apply to PMIC GPIOs (max77620-gpio)

sudo dmesg | grep "registered GPIO"
[    0.534131] gpiochip_setup_dev: registered GPIOs 0 to 255 on device: gpiochip0 (tegra-gpio)
[    0.591897] gpiochip_setup_dev: registered GPIOs 504 to 511 on device: gpiochip1 (max77620-gpio)

• Jetson platforms have two separate GPIO controllers:
  • tegra-gpio → [0–255] On-SoC Tegra GPIOs
  • max77620-gpio → [504–511] PMIC GPIOs
• If the GPIO belongs to tegra-gpio → Use Tegra Port Formula.
• If it belongs to max77620-gpio → The sysfs number is assigned directly by the kernel and the correct calculation is offset = sysfs_gpio - gpiochip_base # Example: 509 - 504 = 5

GPIO Usage

C (libgpiod)Shell (sysfs)Python

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

#define GPIO_BASE "/sys/class/gpio"

static int gpios[] = {228, 149, 62, 66, 63, 168, 169, 200};
static const char *names[] = {
    "GPIO00","GPIO01","GPIO02","GPIO03",
    "GPIO05","GPIO07","GPIO10","GPIO11"
};
#define GPIO_COUNT (sizeof(gpios) / sizeof(gpios[0]))

static int gpio_write_file(const char *path, const char *value) {
    FILE *f = fopen(path, "w");
    if (!f) { perror(path); return -1; }
    fprintf(f, "%s", value);
    fclose(f);
    return 0;
}

static void export_gpio(int gpio) {
    char path[64], buf[8];

    /* Export */
    snprintf(buf, sizeof(buf), "%d", gpio);
    gpio_write_file(GPIO_BASE "/export", buf);

    /* Set direction */
    snprintf(path, sizeof(path), GPIO_BASE "/gpio%d/direction", gpio);
    gpio_write_file(path, "out");
}

static void unexport_gpio(int gpio) {
    char buf[8];
    snprintf(buf, sizeof(buf), "%d", gpio);
    gpio_write_file(GPIO_BASE "/unexport", buf);
}

static void set_value(int gpio, int value) {
    char path[64];
    snprintf(path, sizeof(path), GPIO_BASE "/gpio%d/value", gpio);
    gpio_write_file(path, value ? "1" : "0");
}

int main(void) {
    /* Export all */
    for (size_t i = 0; i < GPIO_COUNT; i++)
        export_gpio(gpios[i]);

    printf("Sequential blink — watch your LED bar...\n");

    for (size_t i = 0; i < GPIO_COUNT; i++) {
        printf("  ON  -> %s (gpio%d)\n", names[i], gpios[i]);
        set_value(gpios[i], 1);
        usleep(500000);   /* 500 ms */
        set_value(gpios[i], 0);
        usleep(200000);   /* 200 ms */
    }

    printf("Done. Cleaning up.\n");
    for (size_t i = 0; i < GPIO_COUNT; i++)
        unexport_gpio(gpios[i]);

    return 0;
}

Compile and run:

    gcc -o test_gpio test_gpio.c
    sudo ./test_gpio

#!/bin/sh

if [ $# -ne 2 ]; then
    echo "Usage: $0 <GPIO_PIN> <VALUE>"
    echo "VALUE: 0 (low) or 1 (high)"
    exit 1
fi

GPIO_PIN="$1"
VALUE="$2"

if [ "$VALUE" != "0" ] && [ "$VALUE" != "1" ]; then
    echo "Error: VALUE must be 0 or 1"
    exit 1
fi

GPIO_PATH="/sys/class/gpio/gpio$GPIO_PIN"

if [ ! -d "$GPIO_PATH" ]; then
    echo "$GPIO_PIN" > /sys/class/gpio/export
    sleep 0.1
fi

echo "out" > "$GPIO_PATH/direction"
echo "$VALUE" > "$GPIO_PATH/value"

Make executable and run:

    chmod +x gpio_set.sh
    sudo ./gpio_set.sh 228 1

#!/usr/bin/env python3
import time
import os

GPIOS  = [228, 149, 62, 66, 63, 168, 169, 200]
NAMES  = ["GPIO00","GPIO01","GPIO02","GPIO03",
        "GPIO05","GPIO07","GPIO10","GPIO11"]
GPIO_BASE = "/sys/class/gpio"

def gpio_write(gpio, filename, value):
    with open(f"{GPIO_BASE}/gpio{gpio}/{filename}", "w") as f:
        f.write(str(value))

def export(gpio):
    export_path = f"{GPIO_BASE}/gpio{gpio}"
    if not os.path.exists(export_path):
        with open(f"{GPIO_BASE}/export", "w") as f:
            f.write(str(gpio))
    gpio_write(gpio, "direction", "out")

def unexport(gpio):
    with open(f"{GPIO_BASE}/unexport", "w") as f:
        f.write(str(gpio))

for gpio in GPIOS:
    export(gpio)

print("Sequential blink — watch your LED bar...")

try:
    for gpio, name in zip(GPIOS, NAMES):
        print(f"  ON  → {name} (gpio{gpio})")
        gpio_write(gpio, "value", 1)
        time.sleep(0.5)
        gpio_write(gpio, "value", 0)
        time.sleep(0.2)
finally:
    print("Done. Cleaning up.")
    for gpio in GPIOS:
        gpio_write(gpio, "value", 0)
        unexport(gpio)

Run:

    sudo python3 test_gpio.py

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