Digital inputs

Pigeon computers are equipped with 8 digital opto-isolated inputs and 4 dry contact inputs.

Digital opto-isolated inputs

The 8 digital opto-isolated inputs are divided into two sections. See the 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 - GPIO

Inputs	GPIO
I1	GPIO12
I2	GPIO13
I3	GPIO18
I4	GPIO19
I5	GPIO20
I6	GPIO21
I7	GPIO22
I8	GPIO23

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 - GPIO

Inputs	GPIO
ID1	GPIO30
ID2	GPIO31
ID3	GPIO32
ID4	GPIO33

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

Software

Bash

Read input I1 (GPIO12) state:

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

Example script which prints state of all digital inputs - read-all-binary-inputs.sh.

wget https://gitlab.com/pigeoncomputers/pigeon-rb-examples/-/raw/master/bash/read-all-binary-inputs.sh
chmod u+x read-all-binary-inputs.sh
./read-all-binary-inputs.sh

The WiringPi library is installed by default. WiringPi comes with a separate program to help manage the GPIO. Read input I1 (GPIO12) state with gpio program:

gpio -g read 12

Python

Read input I1 (GPIO12) state:

python

>>> import RPi.GPIO as GPIO
>>> GPIO.setmode(GPIO.BCM)
>>> GPIO.setup(12, GPIO.IN)
>>> GPIO.input(12)
0

Links

• kernel.org - GPIO