[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.
26 pin header
Header Pin | Pad Name (Default) | GPIO Name | Linux GPIO Number (*) |
|---|---|---|---|
J2 [pin 1] | 3.3V | - | |
J2 [pin 2] | 5V | - | |
J2 [pin 3] | I2C_SDA | # | |
J2 [pin 4] | 5V | - | |
J2 [pin 5] | I2C_SCL | # | |
J2 [pin 6] | GND | - | |
J2 [pin 7] | GPIO 1 | 1 | |
J2 [pin 8] | UART TX | # | |
J2 [pin 9] | GND | - | |
J2 [pin 10] | UART RX | # | |
J2 [pin 12] | GPIO 72 | GPIO3_IO08 | 72 |
J2 [pin 13] | GPIO 71 | 71 | |
J2 [pin 14] | GND | - | |
J2 [pin 15] | GPIO 10 | 10 | |
J2 [pin 16] | GPIO 194 | 194 | |
J2 [pin 17] | 3.3V | - | |
J2 [pin 18] | GPIO 195 | 195 | |
J2 [pin 19] | SPI_MOSI | # | |
J2 [pin 20] | GND | - | |
J2 [pin 21] | SPI_MISO | # | |
J2 [pin 22] | GPIO 67 | 67 | |
J2 [pin 23] | SPI_SCLK | # | |
J2 [pin 24] | ECSPI2_SS0 | # | |
J2 [pin 25] | GND | - | |
J2 [pin 26] | ECSPI2_SS1 | # |
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 & UART can also be muxed to be GPIO
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 & UART can also be muxed to be GPIO
Please have a look at WiringX, which also supports the Hummingboard:
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
echo 1 > /sys/class/gpio/gpioXX/value # or echo 0 > /sys/class/gpio/gpioXX/value |
Get the value of an input pin
cat > /sys/class/gpio/gpioXX/value |
Free GPIO pin
# Unexport GPIO XX echo XX > /sys/class/gpio/unexport |
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 (*)
You can take the GPIO Number from the above table (*)
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.
IMX6 Software Development/Drivers
IMX6 Som Documents
wiringHB