40-pin Header

Carrier boards for the Jetson TX2 NX have a 40-pin expansion header with UART, I²C, SPI, I²S and GPIO signals from the module, and 3.3 V and 5 V supply pins. On the Leetop A206, it is the 2 x 20 header along the right edge of the top side. Seen from above with the USB ports at the bottom, pin 1 is the outer pin at the end nearest the power LED.

Figure 1. The 40-pin header on the Leetop A206. The star marks pin 1.

Figure 2. Pinout of the 40-pin header

warning

The signal voltage of the header is set by the carrier board. On the Leetop A206, all signals are 3.3 V. On another carrier board, check its documentation before you connect a device, and do not connect a device that uses a higher voltage.

Pin Assignments

The pin assignment below is part of the hardware. The device names and commands in the UART, I²C and GPIO sections are for Mixtile OS.

The names are the signal names of the module. For their pins on the edge connector, see 260-pin Connector.

Function	Pin	Pin	Function
3.3 V	1	2	5 V
I2C1_SDA	3	4	5 V
I2C1_SCL	5	6	GND
GPIO09	7	8	UART1_TXD
GND	9	10	UART1_RXD
UART1_RTS*	11	12	I2S0_SCLK
SPI1_SCK	13	14	GND
GPIO12	15	16	SPI1_CS1*
3.3 V	17	18	SPI1_CS0*
SPI0_MOSI	19	20	GND
SPI0_MISO	21	22	SPI1_MISO
SPI0_SCK	23	24	SPI0_CS0*
GND	25	26	SPI0_CS1*
I2C0_SDA	27	28	I2C0_SCL
GPIO01	29	30	GND
GPIO11	31	32	GPIO07
GPIO13	33	34	GND
I2S0_FS	35	36	UART1_CTS*
SPI1_MOSI	37	38	I2S0_DIN
GND	39	40	I2S0_DOUT

UART

UART1 is on pins 8 (TXD) and 10 (RXD), with its RTS and CTS lines for hardware flow control on pins 11 and 36. In Mixtile OS, it is /dev/ttyS1.

To test it with your computer, connect a USB to TTL converter: its GND to pin 6, its TXD to pin 10 and its RXD to pin 8.

1. On your computer, open the converter at 115200 baud, as described in Connect to Core 3588E, with 115200 in place of 1500000.

2. On Core 3588E, install picocom and open the UART at the same speed:

   Core 3588E

   sudo apt update
   sudo apt install -y picocom
   picocom -b 115200 /dev/ttyS1

3. Type in one window.

Expected result: what you type on one side appears on the other. To close picocom, press Ctrl+A, then Ctrl+X.

The user mixtile is in the dialout group, so it can open /dev/ttyS1 without sudo.

I²C

The header has two I²C buses:

Bus	Pins	Device in Mixtile OS
I2C1	3 (SDA), 5 (SCL)	/dev/i2c-1
I2C0	27 (SDA), 28 (SCL)	/dev/i2c-0

I2C0 is shared with the real-time clock on the module, at address 0x51. Do not connect a device with the same address to it.

To find the address of a device, connect its SDA, SCL, GND and supply pins, then scan the bus. For a device on pins 3 and 5:

Core 3588E

i2cdetect -y 1

Expected result: the table shows the device's address, for example 3c for a common OLED display. The user mixtile is in the i2c group, so the I²C tools do not need sudo.

GPIO

Six header pins have named GPIO lines in Mixtile OS, so you can use them without looking up the GPIO chip and line number:

Header pin	Signal	Line name
7	GPIO09	PIN_07
15	GPIO12	PIN_15
29	GPIO01	PIN_29
31	GPIO11	PIN_31
32	GPIO07	PIN_32
33	GPIO13	PIN_33

Control them with the gpioget and gpioset tools, run with sudo:

Ubuntu 24.04 and later, Debian 13

Read pin 7:

Core 3588E

sudo gpioget PIN_07

Set pin 7 high. The pin stays high until you press Ctrl+C:

Core 3588E

sudo gpioset PIN_07=1

Debian 12

Read pin 7:

Core 3588E

sudo gpioget $(sudo gpiofind PIN_07)

Set pin 7 high. The pin stays high until you press Ctrl+C:

Core 3588E

sudo gpioset --mode=signal $(sudo gpiofind PIN_07)=1

To list all named lines, run sudo gpioinfo | grep PIN_.