DIO - Digital Input/Output

The digital inputs and outputs can be controlled / read or set via GPIOs. There are multiple ways on how to access the GPIOs of the Raspberry Pi, one way is by using the so called sysfs through /sys/class/gpio or another by using a library like pigpio.

Below both options are shown. The sysfs option can be used out of the box, while the pigpio library has to be installed first.

Overview of available IOs

Four digital inputs/outputs (either or) are available. If used as output the state can be read back from the associated input.
The table below shows number and function of the available GPIOs.

Name	direction	Accessible via	Connector
dout1	output	GPIO44	X19_DIO1
din1	input	GPIO45	X19_DIO1
dout2	output	GPIO35	X19_DIO2
din2	input	GPIO43	X19_DIO2
dout3	output	GPIO34	X19_DIO3
din3	input	GPIO31	X19_DIO3
dout4	output	GPIO29	X19_DIO4
din4	input	GPIO28	X19_DIO4

Using sysfs to access the GPIOs

Go to the path

pi@raspberry:~ $ cd /sys/class/gpio

Make a GPIO accessible

As an example we use GPIO44 which is digital output 1 (DO1) on the Pi-Tron. Writing the number of a GPIO to the export file in /sys/class/gpiomakes the GPIO accessible.

pi@raspberry:~ $ echo "44" > export

Changing the direction of a GPIO to input or output

For our example we switch the direction of GPIO44 to output so we can turn DO1 on and off.

echo "out" > gpio44/direction

Switching a GPIO on

Writing a 1 to the value property of a GPIO turns the GPIO on. For our example, we write a 1 to GPIO44 to turn it and thus DO1 on.

echo "1" > gpio44/value

Switching a GPIO off

Writing a 0 to the value property of a GPIO turns the GPIO off. For our example, we write a 0 to GPIO44 to turn it and thus DO1 off.

echo "0" > gpio44/value

Using the pigpio library

Install pigpio library

sudo apt update
sudo apt install pigpio

Start the pigpio service

The pigpio library cannot work on its own, it uses an accompanying service program called pigpiod. This service has to be started first, before any access to the GPIOs is possible.

sudo systemctl start pigpiod

If the daemon should start every time the Raspberry Pi/Pi-Tron starts, the following command can be used to enable the services automatic start.

sudo systemctl enable pigpiod

Changing the direction of a GPIO to input or output

To make changes to the GPIOs from the console the program pigs has to be used in order to be able to turn GPIOs on and off.

For our example we switch the direction of GPIO44 to output so we can turn DO1 on and off.

pigs modes 44 w

Switching a GPIO on

Writing a 1 to a GPIO number with pigs turns the GPIO on. For our example, we write a 1 to GPIO44 to turn it and thus DO1 on.

pigs w 44 1

Switching a GPIO off

Writing a 0 to a GPIO number with pigs turns the GPIO off. For our example, we write a 0 to GPIO44 to turn it and thus DO1 off.

pigs w 44 0

Commands to control "pigpiod"

pigpio-daemon turn on automatic start

sudo systemctl enable pigpiod

Deactivate automatic start

sudo systemctl disable pigpiod

pigpio-Daemon manual start:

sudo systemctl start pigpiod

pigpio-Daemon stop:

sudo systemctl stop pigpiod

Show status of the pigpio-Daemon:

sudo systemctl status pigpiod