Hardware Interface Description

Interface overview

• ZERO

Processor

ZERO's SoC is the Amlogic S905Y2. The CPU is a quad-core ARM Cortex-A53 processor. The ARM G31 MP2 GPU makes the S905Y2 fully compatible with OpenGL ES 3.2, Vulkan 1.0 and OpenCL 2.0. The special 2.5D hardware engine will maximize display performance and provide smooth operation.

ZERO

The ZERO has a 32 bits LPDDR 4 chip.The ZERO offers 512MB, 1GB, 2GB and 4GB memory options.

USB OTG (Power Interface)

The ZERO is powered by a Type-C connector with an input voltage of 5V, recommended to use a power adapter with a rated maximum current greater than 2A.
The official Radxa Power PD 30W is recommended.
This interface can be used to connect peripherals such as keyboard, mouse, USB flash drive and so on.

TYPE-c USB3.0

This interface can be used to connect peripherals such as keyboard, mouse, USB flash drive and so on.

40 PIN GPIO

GPIO voltage

GPIO	Voltage	Max
All GPIO	3.3V	3.3V

GPIO Interface

The ZERO provides a 40 pin GPIO header that is compatible with most peer accessories on the market.

**Hint: Actual compatibility is based on usage. **

caution

Depending on the hardware version, one of the pins 35 and 38 is connected to the power LED instead of the 40-pin header. If your design uses these pins, please check the hardware version before purchasing.
GPIOAO_8 and GPIOAO_10 are available in hardware versions v1.51 and higher.
GPIOA_14 and GPIOA_15 are connected to pull-up resistors and USB-C controllers and therefore cannot be used for general GPIOs.
Pin 22 (GPIOC_7) and pin 36 (GPIOH_8) are open-drain pins. This means that they need to be connected to GND or VCC (floating state undefined), and they need an external pull-up when used as inputs. In addition, GPIOH_8 utilizes a 5V logic level.

GPIO number	Function4	Function3	Function2	Function1	Pin#	Pin#	Function1	Function2	Function3	Function4	GPIO number
				+3.3V	1	2	+5.0V
490			I2C_EE_M3_SDA	GPIOA_14	3	4	+5.0V
491			I2C_EE_M3_SCL	GPIOA_15	5	6	GND
415	I2C_AO_S0_SDA	UART_AO_B_RX	I2C_AO_M0_SDA	GPIOAO_3	7	8	GPIOAO_0	UART_AO_A_TXD			412
				GND	9	10	GPIOAO_1	UART_AO_A_RXD			413
414	I2C_AO_S0_SCL	UART_AO_B_TX	I2C_AO_M0_SCL	GPIOAO_2	11	12	GPIOX_9	SPI_A_MISO	TDMA_D0		501
503	TDMA_SCLK	I2C_EE_M1_SCL	SPI_A_SCLK	GPIOX_11	13	14	GND
				SARADC_CH1	15	16	GPIOX_10	SPI_A_SS0	I2C_EE_M1_SDA	TDMA_FS	502
				+3.3V	17	18	GPIOX_8	SPI_A_MOSI	PWM_C	TDMA_D1	500
447		SPI_B_MOSI	UART_EE_C_RTS	GPIOH_4	19	20	GND
448	PWM_F	SPI_B_MISO	UART_EE_C_CTS	GPIOH_5	21	22	GPIOC_7				475
450	I2C_EE_M1_SCL	SPI_B_SCLK	UART_EE_C_TX	GPIOH_7	23	24	GPIOH_6	UART_EE_C_RX	SPI_B_SS0	I2C_EE_M1_SDA	449
				GND	25	26	SARADC_CH2
415	I2C_AO_S0_SDA	UART_AO_B_RX	I2C_AO_M0_SDA	GPIOAO_3	27	28	GPIOAO_2	I2C_AO_M0_SCL	UART_AO_B_TX	I2C_AO_S0_SCL	414
				NC	29	30	GND
				NC	31	32	GPIOAO_4	PWMAO_C			416
				NC	33	34	GND
420			UART_AO_B_TX	GPIOAO_8	35	36	GPIOH_8				451
421			UART_AO_B_RX	GPIOAO_9	37	38	GPIOAO_10	PWMAO_D			422
				GND	39	40	GPIOAO_11	PWMAO_A			423

GPIO numbers

• The GPIOs are divided into two groups, the GPIO AO domain and the GPIO EE domain.
  AO domain: GPIOAO_0 - GPIOAO_11
  EE domain: GPIOA_14 - GPIOA_15 | GPIOH_0 - GPIOH_8 | GPIOX_0 - GPIOX_19
• UART
  AO Domain: UARTAO_A | UARTAO_B
  EE Domain: UART_A | UART_B | UART_C

GPIO Chips	GPIO Names	Basics	Offsets	Formulas
First	GPIOAO_x	412	0-11	Base + Offset
First	GPIOE_x	424	0-2	Base + Offset
Second	GPIOZ_x	427	0-15	Base + Offset
Second	GPIOH_x	443	0-8	Base + Offset
Second	BOOT_x	452	0-15	Base + Offset
Second	GPIOC_x	468	0-7	Base + Offset
Second	GPIOA_x	476	0-15	Base + Offset
Second	GPIOX_x	492	0-19	Base + Offset

Micro HDMI

The Radxa ZERO has a micro HDMI video output port on board, which requires a micro HDMI to standard HDMI cable to connect to the monitor.
The resolution of the HDMI output depends on the monitor, and the Radxa ZERO will adjust to the optimal display resolution according to the monitor.

eMMC

The on-board eMMC is located on the back of the development board for eMMC booting or data storage. We offer options from none to 128GB.

WIFI/BT

ZERO has an ap6212/ap6256/aw-cm256sm WiFi/BT module on board,the specific parameters of each module are listed in the table below.

Module Model	WLAN Standard	Supported Frequency	WLAN Nominal Maximum Throughput	Bluetooth Standard
ap6212	802.11 b/g/n	2.4GHz	72.2Mbps	Bluetooth 4.1
ap6256	802.11 a/b/g/n/ac	2.4GHz/5GHz	433.3Mbps	Bluetooth 5.2
aw-cm256sm	802.11 a/b/g/n/ac	2.4GHz/5GHz	433.3Mbps	Bluetooth 4.2

MicroSD slot

For MicroSD card booting or data storage.

USB BOOT Button

ZERO supports Maskrom mode, which is a special operation mode where the CPU waits for commands from the USB OTG port. When you need to write image to eMMC, you need to use Maskrom button to put it into Maskrom mode.