Digital inputs

Pigeon computer RB700 has 8 digital opto-isolated inputs and 4 dry contact inputs.

Digital opto-isolated inputs

8 digital opto-isolated inputs are divided into two sections. See picture below.

Fig. 1. Digital opto-isolated inputs connection

The following table shows the assignment between the opto-isolated inputs and the GPIO.

Table 1. Digital opto-isolated inputs

Inputs	gpiod	GPIO Sysfs
I1	gpiochip2 8	GPIO496
I2	gpiochip2 9	GPIO497
I3	gpiochip2 10	GPIO498
I4	gpiochip2 11	GPIO499
I5	gpiochip2 12	GPIO500
I6	gpiochip2 13	GPIO501
I7	gpiochip2 14	GPIO502
I8	gpiochip2 15	GPIO503

When the input voltage is in the range of 0 - 5V, the logic state of the GPIO is one (negative logic). When the input voltage is in the range of 10 - 28 V, the state of GPIO is zero.

Table 2. Digital opto-isolated inputs parameters

Parameter	Value
Quantity of inputs	8
Low-level input voltage	0 ... +5 V DC
High-level input voltage	+10 ... +28V DC
Isolation voltage	5 kV RMS
Input resistance	>=10kOhm

Dry contact inputs

The following table shows the assignment between the dry contact inputs and the GPIO.

Table 3. Dry contact inputs

Inputs	gpiod	GPIO Sysfs
ID1	gpiochip0 12	GPIO12
ID2	gpiochip0 13	GPIO13
ID3	gpiochip0 16	GPIO16
ID4	gpiochip0 17	GPIO17

When the input is shorted to GND, the logic state of the GPIO is one. Otherwise, the state of GPIO is zero.

 

Fig. 2. Dry contact inputs connection

Linux kernel GPIO user space interface

gpiod

Installation of the gpiod tools:

apt install gpiod 

Read input I1 state:

gpioget gpiochip2 8

Read input ID1 state:

gpioget gpiochip0 12

GPIO Sysfs Interface for Userspace

Read input I1 (GPIO496) state:

echo "496" > /sys/class/gpio/export
cat /sys/class/gpio/gpio496/value
1
echo "496" > /sys/class/gpio/unexport

Read input ID1 state:

echo "12" > /sys/class/gpio/export
cat /sys/class/gpio/gpio12/value
1
echo "12" > /sys/class/gpio/unexport

 

Links

• kernel.org - libgpiod
• kernel.org - GPIO Sysfs Interface for Userspace