Author: Paul

Bare Bones Install Instructions ( It just worked. ) The bare minimum to get a working installation of the Keyboard+Mouse sharing software Barrier. This can also be used from a Windows machine to a Linux machine or Raspberry Pi.

• 

• 

Barrier – A simple Open Source tool that enables sharing a Keyboard and mouse acrros muliple screens.

Linux Mint 19.x – Install

sudo apt update

sudo apt install snapd

sudo snap install barrier

Raspberry Pi – Install

sudo apt update

sudo apt install barier

Linux Mint 19.x – Run

barrier

Raspberry Pi – Run

barrier

Configure “Server”

In this installation the Server is the Linux 19.x machine. The machine with the Keyboard physically attached is the server. Place the screen in the correct position ( Each screen represents the whole PC, not the actual screen count .) The name of the machine must match the hostname on the raspberry pi. This will be shown in “Screen name:” of the client”

Once you have finished configuring the server, click the Apply button an then the Start button. The start button will change to a “Stop” button and the screen will show “Barrier is running” in the bottom left corner.

Configure Client

You will need the IP Address of the Server from the Server’s Main Screen. Uncheck “Auto Config” enter the IP address. Re-Check Autoconfig. As before press Apply and Stop. The client will connect and you will be able to move your mouse across both screens. ( Try re-starting server-side if it doesn’t work )

NOTES:

• Your mouse point must be on the screen to which you are typing.
• If the client dis-connects first try restarting the server.

Make a single LED Blink using Raspberry PI GPIO and Python.

Using the RPi.GPIO library we can program the LED to blink on and off. The GPIO library gives us easy access to the Pins of the Raspberry Pi.

Take a moment to print out this guide, with a custom template to make hookup dead simple.

https://www.teacherspayteachers.com/Product/Raspberry-Pi-Blink-Project-Guide-5959017

Requirements

• A Raspberry Pi 2/3/4
• A single LED
• 2 Hookup Wires
• A 2.2K Ohm Resistor
• Prototyping Breadboard
• A Raspberry Pi with Rasbian Installed and Running
• Access to the Shell on the Raspberry Pi

First Let’s Wire Up the Pi and the LED

Get Ready

It can be extremely useful to get a PIN template and push it onto the Pins of the PI

I got mine from her : https://www.computerhilfen.de/english/raspberry-pi-gpio-paper-template.html

It is a actual sized and designed to pushed on the pins. Inlcuded in this article is a template custom labelled for this project.

Hook-Up Wires

It is easiest to use hookup wire that has one female end and one male end. The female end is easily pushed onto the RaspberryPI pins and the male end is easily inserted into the Breadboard.

• 

• 

4. Place the resistor from Column 9 to Column 6 on the Breadboard. The resistor has no polarity, so it can be connected in either direction.

That’s all it takes to hook up the LED.

The resistor is a used to limit the amount of current that goes through the LED, it protects the LED from ever getting to much current and burning out.

To aide with wiring here is a diagram from Fritzing:

Now Let’s Add Code

Log on to your Pi using the Pi Desktop or using SSH to get to a Terminal.

Place the following code into a file named rpi_blink.py ( or whatever name you like ), you just copy this code into your text editor or open your text editor and type it in.

import RPi.GPIO as GPIO 
from time import sleep
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BOARD)
GPIO.setup(7, GPIO.OUT, initial=GPIO.LOW)


while True: 
    GPIO.output(7, GPIO.HIGH)
    sleep(1)
    GPIO.output(7, GPIO.LOW)
    sleep(1)

Once you svae the code you can execute the project as follows:

python rpi_blink.py

To stop the code from running press

ctrl-c

Additional Activities

Blink Faster or Slower

To make the LED blink faster you can experiment with different values within the Sleep( ) command.

Try changing the value in Sleep to .1, it should look like this

while True:
    GPIO.output(7, GPIO.HIGH)
    sleep(.1)
    GPIO.output(7, GPIO.LOW)
    sleep(.1)

Make sure you change it in both locations/

Blink at different rates

To make the LED stay on for a different amount of time than it stays off change the values in sleep to differnent values.

A quick blink, can look like this:

while True:
    GPIO.output(7, GPIO.HIGH)
    sleep(.1)
    GPIO.output(7, GPIO.LOW)
    sleep(1)

It will blink for one tenth of a second then stay off for a full second.

When working with electronics this approach can be used to signal different states.

Experiment with different values to see what you can come up with.

If you want details from the source, the library we are using here is fully documented at https://rplcd.readthedocs.io/en/stable/

The Fritzing Diagram can be helpful in wiring up the Pi and the LCD, Fristzing contain pin identifications if you hover over the pin.

The Bare Minimum to get a message on Screen

Wire the Components

The Wiring for the Python version of code is the same as the NodeRED version. Follow the wiring section on that post and return here for the code.

Get The Library

$ sudo pip install RPLCD

Coding Python

The beauty of coding for hardware like an LCD on the Raspberry Pi is that the code is already present where it will be executing. There is no need to compile and upload for a Python Script.

If you prefer to code on your desktop it as simple as copying the resulting Python file to your Raspberry Pi.

For this activity we will be coding in the bash shell via an ssh connection.

ssh pi@192.168.13.14
nano pi_lcd.py

Define the pins that will be used

We will use simple variables to define each of the pins connecting the LCD to the Pi. They could be more abbreviated but to help with clarity we will use longer names.

ENABLE = 31
REGISTER_SELECT = 29
DATA_PIN_D7 = 26
DATA_PIN_D6 = 24
DATA_PIN_D5 = 21
DATA_PIN_D4 = 19

Let’s create any LCD Object using the VAriables we setup above. The RPLCD library does all the hard work all we need to do is import the library and then create an “instance”.

First import the Library

from RPLCD.gpio import CharLCD

Now using the variables we set up earlier we will create the LCD object. The CharLCD class uses keyword args for input. So each argument is a keyword and the value being assigned.

my_lcd = CharLCD(cols=16, rows=2, pin_rs=REGISTER_SELECT, pin_e=ENABLE, pins_data=[DATA_PIN_D7,DATA_PIN_D6,DATA_PIN_D5,DATA_PIN_D4]

That’s all we need, add a line with what text you want to display and you are good to go.

my_lcd.write(u'Message of Hope')

Materials

• Raspberry Pi 3
• 16×2 LCD
• Breadboard
• Hookup Wire
• Trimmer / Potentiometer

Use the Pallete manager to install node-red-contrib-lcd

https://flows.nodered.org/node/node-red-contrib-lcd

Flows

Add the LCD Node to your flow.

The LCD node requires a string indiacting whcih pins of the LCD are connected to which pins of the pi. The format is shown when you double click the node to configure it.

The “Pins, Type” field will give you the format \: RS, EN, D7, D6, D5, D4, ROW, COL

The pin numbering using Board numbering is 6,5,10,9,8,7,2,16

Add the pin numbering and click done.

Board Numbering: 6,5,10,9,8,7,2,16

GPIO Numbering : 31,29, 26,24,21,19, 2,16

Board numbering is simply sequential with even numbers from 2 on the outer row and odd numbers from 1 on the inner row.

Add an inject node:

Connect the inject node to the LCD node.

Double click the inject node and add a string to,

That’s all there is on the NodeRED end, you can deploy now or wait until after wiring.

If you don’t want to wire up the Flow you can just copy in this:

Wiring

The Full Fritzing Diagram is on TeachersPayTeachers.com

Let’s wire up our Pi and LCD as follows. Some color coding can help but the colors are not important.

Connect a Wire from “PIN 2” on the RaspberryPI to the Lower rail ( Red ) on your breadboard. This is +5volts and will be used to power the LCD and the LCD Backlight

Connect a second wire from PIN 6 to the Blue Rail on the Breadboard, this will provide the GRound or NEG for the LCD.

Connect the DATA Lines

We can connect the four Data lines from the LCD to any GPIO Pins on the RaspberryPi. In this example, GPIO 7,8,9,10 were selected for visual location and consecutive numbering. As shown we will be using Blue and White wires for the DATA lines but any color can be used.

Connect GPIO10 to the Breadboard directly below the LCD Pin As Shown. It will be the third pin from the left and likely labelled D8, Pin 14 or sometimes DB7.

Connect GPIO 9 to D7 ( DB6 )

Connect GPIO 8 to D6 ( DB5 )

Connect GPIO 7 to D6 ( DB5 )

Connect the Control Lines

There are only two lines that will be used to control the LCD. Enable and Command Mode. The enable line is basically the on/off switch for the LCD connected to the PI and the Command Mode or “Register Select” informs the LCD if it will be receiving a command to act upon or letters to display.

Connect GPIO5 to the Breadboard colum directly beneath the E pin on the LCD.

Connect GPIO6 to the Breadboard colum directly beneath the RS Pin on the LCD

Wire the Contrast Knob

Trimmer/PotentiometerPotentiometer ) to the LCD VO ( Contrast ). Make sure you coonect the “Wiper” the cneter in this case to the column directly beneath the VO

Connect the Dimmer s( Trimmer/Potentiometer ) legs CW and CCW to +5v and Ground, the polarity of these two determine whether the contrast is increased with a Clockwise turn or a Counter-Clockwise turn.

Deploy the Node and Try a Message