kobol-wiki/docs/helios64/gpio.md

Helios64 provides 16 GPIOs via a 20-Pin header (P5). Those GPIOs are provided via an 16-bit IO Expander PCA9655E connected to I2C bus 2.

Pinout

PIN	Port	Remarks
1	-	3.3V Supply
2	-	5V Supply
3	-	GND
4	EXP_P0_0
5	EXP_P0_1
6	EXP_P0_2
7	EXP_P0_3
8	EXP_P0_4
9	EXP_P0_5
10	EXP_P0_6
11	EXP_P0_7
12	EXP_P1_0
13	EXP_P1_1
14	EXP_P1_2
15	EXP_P1_3
16	EXP_P1_4
17	EXP_P1_5
18	EXP_P1_6
19	EXP_P1_7
20	-	GND

Accessing GPIOs under Linux

If the kernel supports debugfs (CONFIG_DEBUG_FS=y), list of GPIOs can be retrieved with the following command

sudo cat /sys/kernel/debug/gpio

Look for the gpiochip5: GPIOs XXX-YYY section, whereas XXX is first GPIO number and YYY is last GPIO number of IO expander.

gpiochip5: GPIOs 496-511, parent: i2c/2-0020, 2-0020, can sleep:   

Another way to get first GPIO number of the IO expander

cat /sys/bus/i2c/devices/2-0020/gpio/gpiochip*/base

Therefore the mapping between header P5 Pins and Sysfs GPIO numbers will be as described in the following table

GPIO Table

PIN	Sysfs GPIO number	Remarks
1	-	3.3V Supply
2	-	5V Supply
3	-	GND
4	496
5	497
6	498
7	499
8	500
9	501
10	502
11	503
12	504
13	505
14	506
15	507
16	508
17	509
18	510
19	511
20	-	GND

GPIO Control

1. Export the GPIO number you want to use

echo N | sudo tee -a /sys/class/gpio/export

2. Set the direction, "out" for Output or "in" for Input

echo DIRECTION | sudo tee -a /sys/class/gpio/gpioN/direction

3. Now you can read or change the GPIO value

To read GPIO value

cat /sys/class/gpio/gpioN/value

To change GPIO value (only if GPIO set as Output)

echo VALUE | sudo tee -a /sys/class/gpio/gpioN/value

!!! notes Pay attention to the path, /sys/class/gpio/gpioN/ where N is the GPIO number.