HummingBoard Pro/Base GPIOs

Description

[HB GPIO] GPIO, or General-Purpose Input/Output is a mechanism that allows a computing board to provide electrical contacts for signalling to a wide range of external devices. These pins allow commerical and hobbyist projects to do things like communicate with a “breakout board”, or individual physical modules – like a motor.

GPIO interfaces are different than other capabilities on a circuit board (like LVDS or the RTC integration) in that they provide a non-specific electrical interface. While these other interfaces have a set specification and set capability for an intended use (connecting to an LCD panel or a real-time clock, in the cited examples respectively) GPIO pins are used at the developer’s discretion. You could connect a motor. Or a temperature sensor. Or a lock solenoid. Or any one of millions of other device combinations for bringing information into the system – or sending information out from the HummingBoard device.

Pin header schematics

26 pin header

GPIO Header Pinout

Header Pin	Signal	Pad Name	GPIO Name	*Linux GPIO Number ()**

Header Pin	Signal	Pad Name	GPIO Name	*Linux GPIO Number ()**
J2 [pin 1]	3.3V	-	-	-
J2 [pin 2]	5V	-	-	-
J2 [pin 3]	I2C_SDA	EIM_D18	GPIO3_IO18	82
J2 [pin 4]	5V	-	-	-
J2 [pin 5]	I2C_SCL	EIM_D17	GPIO3_IO17	81
J2 [pin 6]	GND	-	-	-
J2 [pin 7]	GPIO 1	GPIO_1	GPIO1_IO01	1
J2 [pin 8]	UART TX	-	-	-
J2 [pin 9]	GND	-	-	-
J2 [pin 10]	UART RX	-	-	-
J2 [pin 11]	GPIO 73	EIM_DA9	GPIO3_IO09	73
J2 [pin 12]	GPIO 72	EIM_DA8	GPIO3_IO08	72
J2 [pin 13]	GPIO 71	EIM_DA7	GPIO3_IO07	71
J2 [pin 14]	GND	-	-	-
J2 [pin 15]	GPIO 70	EIM_DA6	GPIO3_IO06	70
J2 [pin 16]	GPIO 194	SD3_CMD	GPIO7_IO02	194
J2 [pin 17]	3.3V	-	-	-
J2 [pin 18]	GPIO 195	SD3_CLK	GPIO7_IO03	195
J2 [pin 19]	SPI_MOSI	EIM_CS1	GPIO2_IO24	56
J2 [pin 20]	GND	-	-	-
J2 [pin 21]	SPI_MISO	EIM_OE	GPIO2_IO25	57
J2 [pin 22]	GPIO 67	EIM_DA3	GPIO3_IO03	67
J2 [pin 23]	SPI_SCLK	EIM_CS0	GPIO2_IO23	55
J2 [pin 24]	ECSPI2_SS0	EIM_RW	GPIO2_IO26	58
J2 [pin 25]	GND	-	-	-
J2 [pin 26]	ECSPI2_SS1	EIM_LBA	GPIO2_IO27	59

Pins 16 and 18 are actually SD3_CMD and SD3_CLK signals that can be muxed to support flex can TX/RX interface (i.e. those can be connected to an external CAN).
(*) SPI and I2C can also be muxed to be GPIO

Serial UART port access

The UART port for debug can be accessed on the 26 pin header as follows –

Pin 6/9/14/20/25 GND
Pin 1 3.3V
Pin 8 buffered i.MX6 UART TX – pulled up to 3.3v
Pin 10 buffered i.MX6 UART RX – pulled up to 3.3v
Notice that the pin number starts as pin #1 on the edge of the board, towards the micro-USB connector; then number #2 is the one towards the corner of the board.
Accessing GPIO from Linux user space

General

Please have a look at WiringX, which also supports the Hummingboard:

http://wiringx.org/

Manual

The external GPIOs are available under the /sys/class/gpio folder in Linux.
To control on the GPIO pins you need to calculate the GPIO number XX (*) and run the commands below:

Get the current list of reserved GPIO

mount -t debugfs none /sys/kernel/debug
cat /sys/kernel/debug/gpio

Reserve GPIO pin

# Export GPIO XX
echo XX > /sys/class/gpio/export

Set GPIO pin Direction

echo "out" > /sys/class/gpio/gpioXX/direction
# or
echo "in" > /sys/class/gpio/gpioXX/direction

Set the value of an output pin

Get the value of an input pin

Free GPIO pin

To calculate the GPIO number XX:
XX = linux gpio number = (gpio_bank - 1) * 32 + gpio_bit

Example: To calculate the GPIO number of pin header J2 [pin 12] Pad Name GPIO3_IO08

GPIO Bank = 3, GPIO bit = 8

XX = (3 - 1) * 32 + 8 = 72

You can take the GPIO Number from the above table (*)

External Links and References

IMX6 Software Development/Drivers
IMX6 Som Documents
wiringHB
http://wiringx.org/

Developer Center