Hardware interface description

Interface overview

• Radxa ZERO 3W

• Radxa ZERO 3E

Power

Debug Serial Port

The debug serial port of ZERO 3 uses UART2_M0 (40-pin GPIO Pin 8: TX, Pin 10: RX), with a default baud rate of 1500000n8.

UART2_M0 is not recommended for use as a normal UART

UART2_M0 is also the default U-Boot console. If you enable UART2_M0 as a normal serial port through the rsetup overlay, input on the serial port will interrupt the boot process and the device may fail to boot.

If you really need to use UART2_M0, first update the system and bootloader via rsetup, then edit /etc/default/u-boot to uncomment prompt and timeout and set them to 0, and finally run sudo u-boot-update to rebuild the boot configuration.

Ethernet Port

40 PIN GPIO

GPIO voltage

GPIO	Voltage	Maximum
All GPIOs	3.3V	3.63V
SARADC_IN5	3.3V	3.3V

GPIO interface

Radxa ZERO 3 provides a 40-pin GPIO header, which is compatible with most SBC accessories on the market.

Tip: Actual compatibility depends on the use case.

tip

Pin 3, Pin 5, Pin 27, and Pin 28 add extra pull-up resistors for I2C device power supply, so they work abnormally when used as GPIOs.

GPIO number	Function5	Function4	Function3	Function2	Function1	Pin#	Pin#	Function1	Function2	Function3	Function4	Function5	GPIO number
					+3.3V	1	2	+5.0V
32				UART3_RX_M0	GPIO1_A0	3	4	+5.0V
33				UART3_TX_M0	GPIO1_A1	5	6	GND
116		PWM14_M0			GPIO3_C4	7	8	GPIO0_D1	UART2_TX_M0				25
					GND	9	10	GPIO0_D0	UART2_RX_M0				24
97					GPIO3_A1	11	12	GPIO3_A3				I2S3_SCLK_M0	99
98		I2S3_MCLK_M0			GPIO3_A2	13	14	GND
104					GPIO3_B0	15	16	GPIO3_B1	UART4_RX_M1	PWM8_M0			105
					+3.3V	17	18	GPIO3_B2	UART4_TX_M1	PWM9_M0			106
147		PWM15_IR_M1	I2S3_SCLK_M1	SPI3_MOSI_M1	GPIO4_C3	19	20	GND
149	UART9_TX_M1	PWM12_M1	I2S3_SDO_M1	SPI3_MISO_M1	GPIO4_C5	21	22	GPIO3_C1				I2S1_SDO2_M2	113
146		PWM14_M1	I2S3_MCLK_M1	SPI3_CLK_M1	GPIO4_C2	23	24	GPIO4_C6	SPI3_CS0_M1	PWM13_M1	UART9_RX_M1	I2S3_SDI_M1	150
					GND	25	26	NC
138		I2C4_SDA_M0	I2S2_SDI_M1		GPIO4_B2	27	28	GPIO4_B3			I2C4_SCL_M0	I2S2_SDO_M1	139
107		I2C5_SCL_M0			GPIO3_B3	29	30	GND
108		I2C5_SDA_M0			GPIO3_B4	31	32	GPIO3_C2	UART5_TX_M1			I2S1_SDO3_M2	114
115	UART5_RX_M1		I2S1_SCLK_RX_M2		GPIO3_C3	33	34	GND
100			I2S3_LRCK_M0		GPIO3_A4	35	36	GPIO3_A7					103
36			I2S1_SCLK_RX_M0		GPIO1_A4	37	38	GPIO3_A6				I2S3_SDI_M0	102
					GND	39	40	GPIO3_A5				I2S3_SDO_M0	101

USB Function Configuration on 40-Pin

On the ZERO 3W / 3E's 40-Pin interface, the following pins can be configured for USB 2.0:

• USB2_HOST2_DM: Pin number 28, resistor location R46.
• USB2_HOST2_DP: Pin number 27, resistor location R45.

By default, Pin-27 can be configured in software for functions such as GPIO4_B2 (see 40-Pin Pinout), while the USB2_HOST2_DP signal is not activated on the hardware. Pin-28 can be configured in software for functions such as GPIO4_B3 (see 40-Pin Pinout), and the USB2_HOST2_DM signal is also not activated on the hardware. To change these pins to USB functions, please follow the steps below to modify the reserved resistors:

• Remove the 0-ohm resistors at R32 and R39.
• Solder 0-ohm resistors at R45 and R46.

tip

The schematic and resistor locations can be viewed and downloaded from the hardware documentation.Hardware Documentation Download

[Operation Note]

This procedure requires soldering skills, and it is recommended that it be performed by an experienced technician.

USB C

There are two USB TYPE-C ports, one is USB 2.0 OTG port and the other is USB3.0 HOST port. The power supply is USB 2.0 OTG port.

HDMI

Provides a Micro HDMI port.

MIPI CSI

PIN	Name
1	GND
2	MIPI_CSI_RX_D0N
3	MIPI_CSI_RX_D0P
4	GND
5	MIPI_CSI_RX_D1N
6	MIPI_CSI_RX_D1P
7	GND
8	MIPI_CSI_RX_CLK0N
9	MIPI_CSI_RX_CLK0P
10	GND
11	MIPI_CSI_RX_D2N
12	MIPI_CSI_RX_D2P
13	GND
14	MIPI_CSI_RX_D3N
15	MIPI_CSI_RX_D3P
16	GND
17	CAMERAB_PDN_L
18	CIF_CLKOUT
19	GND
20	I2C2_SCL_M1
21	I2C2_SDA_M1
22	VCC_3V3