> For the complete documentation index, see [llms.txt](https://dev.solid-run.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dev.solid-run.com/nxp/imx6/sbc-platform/imx6-other-articles/hummingboard-pro-base-gpios.md).
# 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 (\*)** |
| -------------- | ----------- | ------------ | ------------- | -------------------------- |
| 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 |
{% hint style="info" %}
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
{% endhint %}
### 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:
#### **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**
```
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
{% hint style="info" %}
You can take the GPIO Number from the above table (\*)
{% endhint %}
### External Links and References
* IMX6 Software Development/Drivers
* IMX6 Som Documents
* wiringHB
*
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