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How to use 40-Pin GPIO on reComputer Jetson Boards

This wiki demonstrates how to access and control the 40-pin GPIO of reComputer Jetson Boards. For this wiki, we have used reComputer J4012 as an example. However, the steps will be similar for other reComputer Jetson boards as well.

Before You Start​

Here is some information you need to know before you start working with the 40-Pin GPIO on reComputer Jetson devices.

  • The voltage level per GPIO pin is 3.3V
  • You cannot back power the reComputer Jetson boards via GPIO because of the current limitation from GPIO pins

Find GPIO Name​

Step 1: Open the datasheet of a reComputer Jetson board. Below you can find datasheets of all the reComputer Jetson boards that are available.

Here we have chosen the datasheet of reComputer J4012.

Step 2: Navigate to the section 40 Pin Expansion Header - J10

Step 3: Find the name of the Header Pin # making sure it's default usage is GPIO under the Default Usage / Description column

For example, check Header Pin 15. It's Default Usage is GPIO

Step 4: For the same pin, find the name under Module Pin Name column. In our example, it is GPIO12

Access and Control GPIO​

Now we have 2 different methods to access the GPIOs on the Jetson boards based on the availability of the GPIO labels directly. Using first method, we can directly know the GPIO pin labels after executing a command within the device. However, if the pin labels are not shown directly, you can use the second method.

Method 1​

In this method, the dts file for GPIO is included inside the JetPack version you flash and will have GPIO labelled properly already so that you can obtain the pin labels directly from the device.

Step 1: Enter the terminal of the Jetson device and execute this command

sudo su
cat /sys/kernel/debug/gpio

Step 2: Find the GPIO number corresponding to the Module Pin Name that we got before

In this case, it is gpio-268 corresponding to GPIO12

Step 3: Execute the following inside the terminal to export gpio-268 pin

cd /sys/class/gpio
echo 268 > export

Step 4: Set the direction and set the value. Here direction can be in/ out and the value can be 0/ 1

For example, to set GPIO12 to HIGH

cd gpio268
echo "out" > direction
echo 1 > value

To set GPIO12 to LOW

echo 0 > value

Step 5: To set the GPIO pin that you exported back to default state, execute the following

cd ..
echo 268 > unexport

Method 2​

In this method, the dts file for GPIO is in not included inside the JetPack version you flash and will not have GPIO labelled properly. So we need to refer to another document (pinmux) and obtain this pin label information. Refer the links below according to the SoM.

Step 1: Download the pinmux document according to the SoM you are using. Here we choose the Jetson Orin NX/ Nano document

Step 2: Find the GPIO label (under Customer Usage column) corresponding to the Module Pin Name that we got before. For example, for GPIO12, it is GPIO3_PN.01 and here we refer to PN.01

Step 3: Enter the terminal of the Jetson device and execute this command

sudo su
cat /sys/kernel/debug/gpio

Step 4: Find the GPIO number corresponding to the GPIO label that we got before

In this case, it is gpio-433 corresponding to PN.01 which is also equal to GPIO12

Step 5: Execute the following inside the terminal to export gpio-433 pin

cd /sys/class/gpio
echo 433 > export

Step 6: Set the direction and set the value. Here direction can be in/ out and the value can be 0/ 1

For example, to set GPIO12 to HIGH

cd PN.01
echo "out" > direction
echo 1 > value

To set GPIO12 to LOW

echo 0 > value

Step 7: To set the GPIO pin that you exported back to default state, execute the following

cd ..
echo 433 > unexport

For Jetpack6+​

Similar to method 2, we need to refer to another document (pinmux) and obtain this pin label information. Refer the links below according to the SoM.

Step 1: Download the pinmux document according to the SoM you are using. Here we choose the Jetson Orin NX/ Nano document

Step 2: Find the GPIO label (under Customer Usage column) corresponding to the Module Pin Name that we got before. For example, for GPIO12, it is GPIO3_PN.01 and here we refer to PN.01

Step 3: Enter the terminal of the Jetson device and execute this command

sudo apt update
sudo apt install gpiod

gpioinfo

Step 4: Find the GPIO number corresponding to the GPIO label that we got before

In this case, it is gpiochip0 line85 corresponding to PN.01 which is also equal to GPIO12

Step 5: Then we can use the gpioset command to configure the working mode of the GPIO.

# To set GPIO12 to HIGH
sudo gpioset --mode=wait gpiochip0 85=1
# To set GPIO12 to LOW
sudo gpioset --mode=wait gpiochip0 85=0
info

If you want to learn more about the gpioset command, please refer to this: https://www.acmesystems.it/gpiod

Tech Support & Product Discussion​

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