40-Pin GPIO Interface

The Radxa Dragon Q8B features an onboard 40-pin GPIO (General-Purpose Input/Output) interface, providing highly flexible interface support for hardware expansion.

Users can connect various sensors, actuators, communication modules, displays, and other embedded peripherals via the 40-pin GPIO interface, enabling rapid prototyping and functional verification in fields such as the Internet of Things (IoT), robotics control, and industrial automation.

danger

When using the 40-pin GPIO interface, pay attention to the wiring of the pins and peripherals, and ensure that the pins are connected correctly. Improper operation may result in damage to the device hardware.

GPIO Functions

Dragon Q8B supports connecting external devices to the onboard GPIO pins and provides multiple multiplexed functions, including UART, SPI, and I2C.

Function4	Function3	Function2	Function1	Function0	Pin#	Pin#	Function0	Function1	Function2	Function3
				3V3	1	2	5V
	SPI9_MISO	UART9_CTS	I2C9_SDA	GPIO_41	3	4	5V
	SPI9_MOSI	UART9_RFR	I2C9_SCL	GPIO_42	5	6	GND
			SPI4_CS_3	GPIO_175	7	8	GPIO_63	UART17_TX
				GND	9	10	GPIO_64	UART17_RX
	SPI4_CS_1		I2C5_SDA	GPIO_111	11	12	GPIO_174	UART4_RX	SPI4_CS_0
HS-UART18_CTS	SPI18_MISO	UART18_CTS	I2C18_SDA	GPIO_66	13	14	GND
HS-UART18_RFR	SPI18_MOSI	UART18_RFR	I2C18_SCL	GPIO_67	15	16	GPIO_68	UART18_TX	SPI18_SCKL	HS-UART18_TX
				3.3V	17	18	GPIO_110
	SPI20_MOSI	UART20_RFR	I2C20_SCL	GPIO_88	19	20	GND
	SPI20_MISO	UART20_CTS	I2C20_SDA	GPIO_87	21	22	GPIO_92	SPI20_CS_2
		SPI20_SCKL	UART20_TX	GPIO_89	23	24	GPIO_90	UART20_RX	SPI20_CS_0
				GND	25	26	GPIO_91	SPI20_CS_1
	SPI9_SCKL	UART9_TX	I2C8_SDA	GPIO_43	27	28	GPIO_44	I2C8_SCL	UART9_RX	SPI9_CS_0
		SPI6_CS_0	UART6_RX	GPIO_157	29	30	GND
		SPI6_SCKL	UART6_TX	GPIO_156	31	32	GPIO_114	CCI_I2C_SCL0	GCC_GP2_CLK_MIRA
		GCC_GP3_CLK_MRIA	CCI_I2C_SDA1	GPIO_115	33	34	GND
	SPI4_MISO	UART4_CTS	I2C4_SDA	GPIO_171	35	36	GPIO_112	I2C5_SCL	SPI4_CS_2
	HS-UART18_RX	SPI18_CS_0	UART18_RX	GPIO_69	37	38	GPIO_172	I2C4_SCL	UART4_RFR	SPI4_MOSI
				GND	39	40	GPIO_173	UART4_TX	SPI4_SCKL

GPIO Usage

This section demonstrates common GPIO usage through the onboard 40-pin GPIO interface.

Install Python Library

Use the python-periphery library to control GPIO pins.

radxa@dragon-q8b$

sudo apt update
sudo apt install -y python3-periphery

GPIO Output/Input

Hardware Requirements

• Board
• Dupont wire

Software Requirements

• python-periphery library

Test Code

The following code uses the python-periphery library to control the GPIO_42 pin for outputting high/low levels and reads the GPIO_42 pin's state through the GPIO_175 pin.

gpio_output_input.py

from periphery import GPIO
import time

def gpio_output_with_feedback():
    # GPIO Configuration (modify pin numbers based on your hardware)
    # GPIO_42 (output)  → maps to line 42 of /dev/gpiochip4
    # GPIO_175 (input)  → maps to line 175 of /dev/gpiochip4
    OUTPUT_PIN_CHIP = "/dev/gpiochip4"
    OUTPUT_PIN_NUMBER = 42    # GPIO_42 (output pin, controlled by the script)
    INPUT_PIN_NUMBER = 175    # GPIO_175 (input pin, reads GPIO_42's output state)

    # Initialize GPIO objects as None first (for safe release later)
    gpio_out = None
    gpio_in = None

    try:
        # Initialize GPIO_42 as OUTPUT mode
        gpio_out = GPIO(OUTPUT_PIN_CHIP, OUTPUT_PIN_NUMBER, "out")
        # Initialize GPIO_175 as INPUT mode
        gpio_in = GPIO(OUTPUT_PIN_CHIP, INPUT_PIN_NUMBER, "in")

        # Print test initialization info
        print("=== GPIO Output-Input Feedback Test Started ===")
        print(f"Controlled Pin (GPIO_42): {OUTPUT_PIN_CHIP} - Line {OUTPUT_PIN_NUMBER} (OUTPUT)")
        print(f"Monitoring Pin (GPIO_175): {OUTPUT_PIN_CHIP} - Line {INPUT_PIN_NUMBER} (INPUT)")
        print("Test Behavior: GPIO_42 toggles HIGH/LOW every 1s; GPIO_175 verifies GPIO_42's state")
        print("Press Ctrl+C to stop the test\n")

        # Main loop: Toggle GPIO_42 and read GPIO_175 feedback
        while True:
            # 1. Set GPIO_42 to HIGH level
            gpio_out.write(True)
            time.sleep(0.1)  # Short delay for signal stabilization (avoid read lag)
            gpio175_reading = gpio_in.read()
            print(f"GPIO_42 Output: HIGH (True) | GPIO_175 Reading: {gpio175_reading}")

            # Keep GPIO_42 HIGH for 1 second
            time.sleep(1)

            # 2. Set GPIO_42 to LOW level
            gpio_out.write(False)
            time.sleep(0.1)  # Short delay for signal stabilization
            gpio175_reading = gpio_in.read()
            print(f"GPIO_42 Output: LOW (False) | GPIO_175 Reading: {gpio175_reading}")

            # Keep GPIO_42 LOW for 1 second
            time.sleep(1)

    # Handle user-initiated exit (Ctrl+C)
    except KeyboardInterrupt:
        print("\n\nTest stopped by user (Ctrl+C)")
    # Handle other unexpected errors (e.g., GPIO access failure)
    except Exception as e:
        print(f"\nError during test: {str(e)}")
    # Ensure GPIO resources are released even if an error occurs
    finally:
        print("\nReleasing GPIO resources...")
        # Safely close GPIO_42 (set to LOW first to avoid residual high level)
        if gpio_out:
            try:
                gpio_out.write(False)
                gpio_out.close()
                print(f"Successfully closed GPIO_42 (Line {OUTPUT_PIN_NUMBER})")
            except Exception as close_err:
                print(f"Failed to close GPIO_42 (Line {OUTPUT_PIN_NUMBER}): {str(close_err)}")
        # Safely close GPIO_175
        if gpio_in:
            try:
                gpio_in.close()
                print(f"Successfully closed GPIO_175 (Line {INPUT_PIN_NUMBER})")
            except Exception as close_err:
                print(f"Failed to close GPIO_175 (Line {INPUT_PIN_NUMBER}): {str(close_err)}")
        print("Resource release complete.")

# Run the test when the script is executed directly
if __name__ == "__main__":
    gpio_output_with_feedback()

Test Steps

1. Short-circuit the GPIO_42 and GPIO_175 pins using a Dupont wire (these are pins 5 and 7 of the 40-pin header, respectively)

2. Save the code as gpio_output_input.py

3. Run the test code using the command: sudo python3 gpio_output_input.py

Expected Results

The terminal will display the output level of GPIO_42 and the level read by GPIO_175.

• False represents a LOW level
• True represents a HIGH level