Digital inputs
The Pigeon RB700 computer has 8 opto-isolated digital inputs and 4 dry contact inputs.
Digital optoisolated inputs
The 8 opto-isolated digital inputs are divided into two sections. See the diagram below.
Fig. 1. Digital opto-isolated inputs connection
The following table shows the mapping between the opto-isolated inputs and GPIO.
Table 1. Digital opto-isolated inputs
| INPUTS | GPIOD | GPIO SYSFS | GPIO SYSFS kernel below 6.6 |
|---|---|---|---|
| I1 | gpiochip2 8 | GPIO586 | GPIO496 |
| I2 | gpiochip2 9 | GPIO587 | GPIO497 |
| I3 | gpiochip2 10 | GPIO588 | GPIO498 |
| I4 | gpiochip2 11 | GPIO589 | GPIO499 |
| I5 | gpiochip2 12 | GPIO590 | GPIO500 |
| I6 | gpiochip2 13 | GPIO591 | GPIO501 |
| I7 | gpiochip2 14 | GPIO592 | GPIO502 |
| I8 | gpiochip2 15 | GPIO593 | GPIO503 |
When the input voltage is between 0V and 5V, the GPIO logic state is high (negative logic). When the input voltage is between 10V and 28V, the GPIO state is low.
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 mapping between the dry contact inputs and GPIO.
Table 3. Dry contact inputs
| INPUTS | GPIOD | GPIO SYSFS | GPIO SYSFS kernel below 6.6 |
|---|---|---|---|
| ID1 | gpiochip0 12 | GPIO590 | GPIO12 |
| ID2 | gpiochip0 13 | GPIO591 | GPIO13 |
| ID3 | gpiochip0 16 | GPIO594 | GPIO16 |
| ID4 | gpiochip0 17 | GPIO595 | GPIO17 |
When the input is shorted to GND, the GPIO logic state is high. Otherwise, the GPIO state is low.
Fig. 2. Dry contact inputs connection
Linux kernel GPIO user space interface
gpiod
Install 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 state:
$ echo "586" > /sys/class/gpio/export
$ cat /sys/class/gpio/gpio586/value
1
$ echo "586" > /sys/class/gpio/unexport Read input ID1 state:
$ echo "590" > /sys/class/gpio/export
$ cat /sys/class/gpio/gpio590/value
1
$ echo "590" > /sys/class/gpio/unexport Direct control via the I2C interface
To control the opto-isolated inputs directly via the I2C interface, comment out the following line in the /boot/firmware/config.txt file (or /boot/config.txt in older distributions):
dtoverlay=mcp23017,addr=0x20,gpiopin=23 Otherwise, you will receive the following message:
Error: Could not set address to 0x20: Device or resource busy. Reading input I1:
gpio -x mcp23017:100:0x20 read 108 To read the next inputs, change the last argument accordingly: I2=109, I3=110, and so on.
Information for Codesys Users
If you want to use binary inputs/outputs in CODESYS, comment out the following line in the /boot/firmware/config.txt file (or /boot/config.txt in older distributions):
dtoverlay=mcp23017,addr=0x20,gpiopin=23