APEX ORIN NX II GPIO Digital Output#

Hardware Connection#

Interface Pin Definition#

Connector

DB9 Pin Number

Description

Utility Channel Index

DI_0

1

GPIO IN

0

DI_1

2

GPIO IN

1

DO_0

3

GPIO OUT

0

DO_1

4

GPIO OUT

1

GND

6-9

Ground


Connector

DB9 Pin Number

Description

Utility Channel Index

DI_2

1

GPIO IN

2

DI_3

2

GPIO IN

3

DO_2

3

GPIO OUT

2

DO_3

4

GPIO OUT

3

GND

6-9

Ground


Use this channel index with the DI or DO utility shown below.

DO Hardware Specifications#

The rated DO operating range is 0–24 V. The permitted reference-voltage range (Vref) is 0–36 V. The permitted reference-voltage range is distinct from the product’s rated operating range.

Hardware Specifications

Vref

0~36V

Nominal Load Current

100 mA

DO Usage#

GPIO usage examples are shown below

sudo /opt/miivii/features/gpio/bin/miivii_set_do_level <DO number> <level: 0/1> <duration(seconds) of level>

# <DO number>: DO index; 0 represents DO0, 1 represents DO1, and so on.
# <level: 0/1>: required logic level; 0 for low, 1 for high.
# <duration(seconds) of level>: duration in seconds. DO remains at <level: 0/1> during this period, then returns to its previous state.
# Note: GPIO SYSFS was marked obsolete starting with Linux kernel 4.8, and is no longer supported starting with Jetpack 6.0. GPIO operations using libgpiod are recommended. Operation without a hold duration is therefore not supported.

# Example: set DO0 high for 20 seconds.
#sudo /opt/miivii/features/gpio/bin/miivii_set_do_level 0 1 20

Compile the Sample Code

cp -r /opt/miivii/features ~/
cd ~/features/gpio
sudo make;

GPIO Troubleshooting#

​1. Permissions and Pin Ownership​#

​Symptom​

​Possible Cause​

​Solution​

Running echo X > export results in

the message Device or resource busy”

GPIO is already in use by another driver or process

1. Check what is using the pin:cat /sys/kernel/debug/gpio

2. Terminate the process using the pin:lsof /sys/class/gpio/gpioX/value

3. Force release:echo X > unexport → Restart the system

Accessing /sys/class/gpio files: permission denied​

The user is not in the gpio group or is not using sudo

1. Add the user to the group:sudo usermod -aG gpio <user>

2. Change file permissions:sudo chmod 0660 /sys/class/gpio/gpioX/value

2. Abnormal Logic Levels​#

​Symptom​

​Possible Cause​

​Solution​

​Unstable Output Level​

1. Power supply interference or poor grounding

2. A PCB signal trace crosses a split plane, causing an impedance discontinuity<br>3. Load current exceeds the limit

1. Add decoupling capacitors for filtering

2. Check PCB routing and avoid signal traces crossing split power planes

3. Use an external MOSFET to drive high-current loads

​Incorrect Input Value​

1. Pull-up or pull-down resistors are not configured

2. External voltage is outside the allowable range

1. Configure a pull-up in software:echo pullup > /sys/class/gpio/gpioX/direction

2. Add a 4.7kΩ pull-up resistor or use a level shifter

​System Hangs When Reading the Level in Output Mode​

1. Incorrect access to the input data register (IDR)

2. A short circuit in the external circuit

1. Read the state from the output data register instead

2. Add a 100Ω series current-limiting resistor to prevent overcurrent

​3. Interrupt and Event Detection Issues​#

​Symptom​

​Possible Cause​

​Solution​

​Interrupt Does Not Respond(edge triggering fails)

1. Incorrect interrupt type configuration

2. ISR blocks for too long

1. Confirm the trigger edge:echo rising > /sys/class/gpio/gpioX/edge

2. Optimize the ISR: use perf top to analyze execution time and split long tasks

​False Event Detection(for example, a high-level event is triggered unexpectedly)

1. Signal noise

2. Poor solder joint or contact at the pin

1. Add software debouncing: in sysfs, configure the debounce value

2. Use shielded cable to reduce interference or add an RC filter

​4. Function Configuration Conflicts​#

​Symptom​

​Possible Cause​

​Solution​

GPIO Direction Setting Does Not Take Effect(cannot switch between input and output)

1. Pin multiplexing conflict, such as a pin assigned to I2C

2. Driver is not loaded

1. Check the device tree: confirm that apex_ad10.dts does not assign the pin to another function

2. Load the driver:modprobe gpio_chip_cdev

​Switching the Same Pin between Output and Input Fails​

1. Mode switching timing conflict

2. Interrupt preemption causes inconsistent state

1. Perform the operation with interrupts disabled:local_irq_save()

2. Cache the state in a global variable to avoid frequent switching