Jetson Nano GPIO说明

1. Jetson.GPIO 库

Jetson.GPIO库 已经预装在Nano，无需再安装其他GPIO Python库，如果安装了其他GPIO库需先卸载方可以正常适用Jetson.GPIO, 预安装路径：

/opt/nvidia/jetson-gpio

运行Jetson.GPIO前需运行以下步骤，建立GPIO 运行环境
步骤一 - 设置运行权限Setup permissions

sudo groupadd -f -r gpio
sudo usermod -a -G gpio jetbot  #$USER
sudo cp /opt/nvidia/jetson-gpio/etc/99-gpio.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules && sudo udevadm trigger

sudo reboot now

步骤二 - Python 代码引用
添加如下Python 代码后，才可以调用 import the RPi.GPIO (或者 motorhat library等)

import sys
sys.path.append('/opt/nvidia/jetson-gpio/lib/python/')
sys.path.append('/opt/nvidia/jetson-gpio/lib/python/Jetson/GPIO')
import Jetson.GPIO

步骤三：Python GPIO 案例
GPIO Mode

GPIO.setmode(GPIO.BOARD)
# or
GPIO.setmode(GPIO.BCM)
# or
GPIO.setmode(GPIO.CVM)
# or
GPIO.setmode(GPIO.TEGRA_SOC)

如下已验证代码案例（测量J41 PIN13，每隔2s 置高置低即0/1/0/1）

#!/usr/bin/env python
#BCM 是Broadcom SOC GPIO序列号，此处需修改为BOARD
#即Nano载板的40Pin GPIO序列号，参考上图<Nano_J41_40Pin.png>

#import jetson gpio
import sys
sys.path.append('/opt/nvidia/jetson-gpio/lib/python/')
sys.path.append('/opt/nvidia/jetson-gpio/lib/python/Jetson/GPIO')

import Jetson.GPIO as GPIO
import time

# Pin Definitions
output_pin = 13  #J41_BOARD_PIN13---gpio14/GPIO.B06/SPI2_SCK

def main():
    # Pin Setup:
    # Board pin-numbering scheme
    GPIO.setmode(GPIO.BOARD)
    # set pin as an output pin with optional initial state of HIGH
    GPIO.setup(output_pin, GPIO.OUT, initial=GPIO.HIGH)

    print("Starting demo now! Press CTRL+C to exit")
    curr_value = GPIO.HIGH
    try:
        while True:
            time.sleep(2)
            # Toggle the output every second
            print("Outputting {} to pin {}".format(curr_value, output_pin))
            GPIO.output(output_pin, curr_value)
            curr_value ^= GPIO.HIGH
    finally:
        GPIO.cleanup()

if __name__ == '__main__':
    main()

2. 超声波HC-SR04 应用案例

#!/usr/bin/env python
#BCM 是Broadcom SOC GPIO序列号，此处需修改为BOARD
#即Nano载板的40Pin GPIO序列号，参考上图<Nano_J41_40Pin.png>

import Jetson.GPIO as GPIO
import time

# Pin Definitions
trig_output_pin = 13  #发射PIN，J41_BOARD_PIN13---gpio14/GPIO.B06/SPI2_SCK
echo_input_pin = 18  #接收PIN，J41_BOARD_PIN18---gpio15/GPIO.B07/SPI2_CS0

def main():
    # Pin Setup:
    # Board pin-numbering scheme
    GPIO.setmode(GPIO.BOARD)
    # set pin as an output pin with optional initial state of LOW
    GPIO.setup(trig_output_pin, GPIO.OUT, initial=GPIO.LOW)
    GPIO.setup(echo_input_pin, GPIO.IN)
    #value = GPIO.input(echo_input_pin)
    #print("Value read from pin {} : {}".format(echo_input_pin,value_str))

    print("Starting Measure now! Press CTRL+C to exit")
    try:
        while True:
            # Toggle the output every second
            GPIO.output(trig_output_pin, GPIO.HIGH)
            time.sleep(0.00001)
            GPIO.output(trig_output_pin, GPIO.LOW)
         
            pulse_start = time.time()
            while GPIO.input(echo_input_pin)==0:
                    pulse_start = time.time()

                    pulse_end = time.time()
                    while GPIO.input(echo_input_pin)==1:
                            pulse_end = time.time()

                            pulse_duration = pulse_end - pulse_start
                            distance = pulse_duration * 17150
                            distance = round(distance, 2)

                            print ("Distance" , distance)
            
    finally:
        GPIO.cleanup()


if __name__ == '__main__':
    main()

3. Jetson Nano GPIO一些说明：

Jetson.GPIO Library doesn't support PWM**
（不支持PWM，如需要PWM需外接一个I2C转PWM信号的板子）
However, the following I2C controlled board can generate PWM signals up to ~1.6kHz and should have Python libraries available.
https://www.adafruit.com/product/815

You could potentially connect this to whatever H-Bridge meets the power requirements of your application. The motor driver we used for JetBot actually combines this chip and multiple H-bridge on the same board.
https://www.adafruit.com/product/2927

PS:
NVIDIA Forum:
Nano GPIO Python support
https://pypi.org/project/Jetson.GPIO/

Jetson Nano GPIO 代码目录及部分说明
GPIO DTS:
hardware/nvidia/platform/t210/porg/kernel-dts/porg-platforms/tegra210-porg-gpio-p3448-0002-a02.dtsi

P37-gpio12-GPIO.B04
P22-gpio13-GPIO.B05
P13-gpio14-GPIO.B06
P18-gpio15-GPIO.B07
VDD-USB-HUB-EN gpio151-GPIO.S07

IMX219 DTS:
hardware\nvidia\platform\t210\porg\kernel-dts\porg-platforms\tegra210-porg-camera-rbpcv2-imx219.dtsi