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Protocol supports communication via GPIO (General Purpose I/O) interface on inputs/outputs of Raspberry PI and computers built on a RPI Compute Module. Currently supported are:
- Raspberry PI (version 2 and 3) based on pigpio library - communication via GPIO (General Purpose I/O) pins
- Techbase NPE - X500 M3 (DIN-mounted industrial computer built on RPI Compute Module 3 with optional industrial inputs and outputs)
The communication was tested with Raspberry PI (version 3) and NPE - X500-M3-MAX-3G.
The protocol allows For Raspberry PI, the protocol supports reading of digital inputs (instantaneous values as well as counting signal changes with an optional time filter) and setting digital outputs to a constant value or pulse-width modulation (PWM).
For NPE X500 the protocol supports reading of digital and analog inputs and status of user button and analog inputs (in case of NPE-X500 also a value of user button), writing to digital outputs (for NPE-X500 also , setting relay outputs, working with user LEDs and a buzzer.
Note: On Raspberry PI, the KOM process must be run under the root user to gain access to the GPIO. It is possible to achieve by setting the setuid bit for the kom binary. Under the user pi, you can do the following:
cd /opt/d2000/bin
sudo chown root kom
sudo chmod 4755 kom
Note: On NPE X500, the KOM process must be run under the root user to gain access to the GPIO (see the previous note for Raspberry PI). An alternative is adding user d2000 to groups and setting appropriate access rights. Under the root user, you can do the following:
sudo usermod -a -G gpio d2000
For access to serial ports also:
sudo usermod -a -G dialout d2000
In order for the d2000 user to access the LEDs and the buzzer, it is necessary to set the rights for the respective files each time the computer starts up. Create a file d2000init in the /etc/init.d directory containing:
#!/bin/bash
### BEGIN INIT INFO
# Provides: script
# Required-Start: $all
# Required-Stop:
# Default-Start: 2 3 4 5
# Default-Stop:
# Short-Description: D2000Kom
# Description: Support for D2000 KOM (work with leds/buzzer)
### END INIT INFO
DESC="Set permissions for LED/BUZZER for D2000 KOM"
chmod -R o+w /sys/class/leds/LED1
chmod -R o+w /sys/class/leds/LED2
chmod -R o+w /sys/class/leds/BUZZER
Then run:
chmod 755 /etc/init.d/d2000init
update-rc.d d2000init defaults
| Kotva | ||||
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| Full name | Description | Units / size | Default value | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Type of device. Currently supported are::
| - | Raspberry PI | ||||||
| Name of library with communication functions for a particular device. The used values are:
| - | - | ||||||
| Delay after one reading of the values of all I/O tags. Using this parameter, it is possible to control the reading frequency more finely than using the polling parameters in the configuration of time parameters of the station. | ms | 1 |
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| Address | Description | I/O tag type | Examples |
|---|---|---|---|
DI,id | The GPIO pin will be configured as a digital input. If the voltage of 3.3V is applied to it, the value of input will be 1. If 0V (ground) voltage is applied to it, the value of input will be 0. | Di, Ci, Ai | DI,25 DI_UP,24 |
DO,id | The GPIO pin will be configured as a digital output. If a value of 1 is written to it, the output will be 3.3V. If 0 is written, output voltage will be 0V (ground). | Dout, Co, Ao | DO,24 |
| TRIGGER_TOON,id[,filter] TRIGGER_TOON_UP,id[,filter] TRIGGER_TOON_DOWN,id[,filter] TRIGGER_TOOFF,id[,filter] TRIGGER_TOOFF_UP,id[,filter] TRIGGER_TOOFF_DOWN,id[,filter] TRIGGER,id[,filter] TRIGGER_UP,id[,filter] TRIGGER_DOWN,id[,filter] | The GPIO pin will be configured as an counter of input events with an optional filter. The counter can register rising signal edges 0V → 3.3V (TRIGGER_UPTOON), falling edges 3.3V → 0V (TRIGGER_DOWNTOOFF) and arbitrary any signal changes (TRIGGER)without TOON/TOOFF). | Ci, Ai | TRIGGER,24 |
| PWM,id | The GPIO pin will be configured as PWM (pulse width modulation) output. It is then possible to write values 0-255 controlling the width of pulse from fully off to fully on. | Dout, Co, Ao | PWM,12 |
| REVISON | The revision of the hardware (the number from the "Revision" line from the /proc/cpuinfo file. For example, for RPI 3 in this file is the contains a row | Ci | REVISON |
I/O tag addresses for NPE - X500
In the following table, id defines the number of input/output (e.g. DI, DO, AO). The number of inputs and outputs depends on the particular model. The notes are referring to the NPE - X500-M3-MAX-3G that was tested.
Note 1: Output points whose addresses contain _BUF use a buffered writing. This allows the values of such objects not only to be written, but also to be read, which can be useful, for example, after the start of the KOM process.
Note 2: With the tested model, the reading of the digital input took less than 1 ms, while the reading the analog input took approximately 20 ms.
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