112 lines
2.4 KiB
Markdown
112 lines
2.4 KiB
Markdown
Helios64 provides 16 GPIOs via a 20-Pin header (P5). Those GPIOs are provided via an 16-bit IO Expander [PCA9655E](http://www.onsemi.com/PowerSolutions/product.do?id=PCA9655E) connected to I2C bus 2.
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## Pinout
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| PIN | Port | Remarks |
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|-----|------|-------------|
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| 1 | - | 3.3V Supply |
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| 2 | - | 5V Supply |
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| 3 | - | GND |
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| 4 | EXP_P0_0 | |
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| 5 | EXP_P0_1 | |
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| 6 | EXP_P0_2 | |
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| 7 | EXP_P0_3 | |
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| 8 | EXP_P0_4 | |
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| 9 | EXP_P0_5 | |
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| 10 | EXP_P0_6 | |
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| 11 | EXP_P0_7 | |
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| 12 | EXP_P1_0 | |
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| 13 | EXP_P1_1 | |
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| 14 | EXP_P1_2 | |
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| 15 | EXP_P1_3 | |
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| 16 | EXP_P1_4 | |
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| 17 | EXP_P1_5 | |
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| 18 | EXP_P1_6 | |
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| 19 | EXP_P1_7 | |
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| 20 | - | GND |
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## Accessing GPIOs under Linux
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If the kernel supports debugfs (*CONFIG_DEBUG_FS=y*), list of GPIOs can be retrieved with the following command
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```bash
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sudo cat /sys/kernel/debug/gpio
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```
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Look for the **gpiochip5: GPIOs XXX-YYY** section, whereas **XXX** is first GPIO number and **YYY** is last GPIO number of IO expander.
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```
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gpiochip5: GPIOs 496-511, parent: i2c/2-0020, 2-0020, can sleep:
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```
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Another way to get first GPIO number of the IO expander
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```
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cat /sys/bus/i2c/devices/2-0020/gpio/gpiochip*/base
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```
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Therefore the mapping between header P5 Pins and Sysfs GPIO numbers will be as described in the following table
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### GPIO Table
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| PIN | Sysfs GPIO number | Remarks |
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|-----|------|-------------|
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| 1 | - | 3.3V Supply |
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| 2 | - | 5V Supply |
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| 3 | - | GND |
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| 4 | 496 | |
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| 5 | 497 | |
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| 6 | 498 | |
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| 7 | 499 | |
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| 8 | 500 | |
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| 9 | 501 | |
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| 10 | 502 | |
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| 11 | 503 | |
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| 12 | 504 | |
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| 13 | 505 | |
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| 14 | 506 | |
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| 15 | 507 | |
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| 16 | 508 | |
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| 17 | 509 | |
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| 18 | 510 | |
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| 19 | 511 | |
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| 20 | - | GND |
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### GPIO Control
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**1.** Export the GPIO number you want to use
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```
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echo N | sudo tee -a /sys/class/gpio/export
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```
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( *N* is the GPIO number you want to export )
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**2.** Set the direction, "out" for Output or "in" for Input
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```
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echo DIRECTION | sudo tee -a /sys/class/gpio/gpioN/direction
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```
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(*DIRECTION* value is "out" or "in")
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**3.** Now you can read or change the GPIO value
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To read GPIO value
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```
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cat /sys/class/gpio/gpioN/value
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```
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To change GPIO value (only if GPIO set as Output)
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```
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echo VALUE | sudo tee -a /sys/class/gpio/gpioN/value
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```
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!!! notes
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Pay attention to the path, /sys/class/gpio/gpio**N**/ where **N** is the GPIO number.
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