lec37_toggleLED

Lecture 37 Get Started with Raspberry PI and PyQt

1. Introduction to the Raspberry PI (RPI)

Raspberry Pi is a small single board computer. By connecting peripherals like Keyboard, mouse, display to the Raspberry Pi, it will act as a mini personal computer. Raspberry Pi is popularly used for real time Image/Video Processing, IoT based applications and Robotics applications.

Raspberry Pi is slower than laptop or desktop but is still a computer which can provide all the expected features or abilities, at a low power consumption. Raspberry Pi Foundation officially provides Debian based Raspbian OS. Also, they provide NOOBS OS for Raspberry Pi. We can install several Third-Party versions of OS like Ubuntu, Archlinux, RISC OS, Windows 10 IOT Core, etc. Raspbian OS is official Operating System available for free to use. This OS is efficiently optimized to use with Raspberry Pi. Raspbian have GUI which includes tools for Browsing, Python programming, office, games, etc. We should use SD card (minimum 8 GB recommended) to store the OS (operating System).

Raspberry Pi is more than computer as it provides access to the on-chip hardware i.e. GPIOs for developing an application. By accessing GPIO, we can connect devices like LED, motors, sensors, etc and can control them too. It has ARM based Broadcom Processor SoC along with on-chip GPU (Graphics Processing Unit). The CPU speed of Raspberry Pi varies from 700 MHz to 1.2 GHz. Also, it has on-board SDRAM that ranges from 256 MB to 1 GB. Raspberry Pi also provides on-chip SPI, I2C, I2S and UART modules. There are different versions of raspberry pi available as listed below:
Raspberry Pi 1 Model A
Raspberry Pi 1 Model A+
Raspberry Pi 1 Model B
Raspberry Pi 1 Model B+
Raspberry Pi 2 Model B
Raspberry Pi 3 Model B
Raspberry
Pi Zero

Caution:

Please try to not touch the metal pins/compoments on the board. Try to hold the edges. The static shock from your finger can kill the IC chips on the board:

2. The First Experiment with the PI board
2.1 Set up your RPI board
The following figure shows the parts needed for the experiment:
A RPI board
A mouse
A power supply
a keyboard
a SD card (has the Debian Linux OS in there)

I found a very nice case for the RPI board to make this little board looks more like a real computer.

Before you put your RPI board into the case, make sure you have the SD card inserterd into the board

First, install the four rubber corner protectors at the four corners of the plastic support of the touchpad:

Then connect the case to the support at the joint use the given bolts and nuts:

Plug in the Flexible Flat Cable (FFC) to the touch pad control board (not to the RPI board yet!!!!):

In the following figure, the 'metal' side of the FFC is facing UP.

Gentally bend the FFC and mount your touch pad to the box:

Screw in the bolts to mount the PRI to the cover:

Gentally put the board into the slot:

Mount it to the holder use the stainless steel screws:

Put the board cover at the back to the case:

Connect the microUSB adapter to the USB port of the PRI board and the touch pad control board:

The other end of the adapter should be connected to the power supply.

Then plug in the mouse and keyboard to the RPI board, your mini RPI computer is ready to roll!!

You can also follow the video at the link below to assmeble the case and the RPI:
https://www.youtube.com/watch?v=XKVd5638T_8

2.2 Print a label of your name and put it at the back of the case:
For the rest of the lectures, please always take your RPI board.

2.3 Fix the keyboard incorrect character issue (@, #, & .....)

Turn on the command line terminal and type 'sudo raspi-config':

Then move the arrows on the keyboard to select 'Localisation Options':

Then select 'Change Keyboard Layout':

Then select 'Generic 101-key PC':

Then 'other':

Then:

Then:

Then:

Then:

Then:

Then come back to the starting window, select 'Finish'.

You can also find the instruction for changing the keyboard issue at the link below:
https://www.youtube.com/watch?v=t02Rc8NPt5w

2.4 Update your RPI (important)

Connect the RPI board to the FLC-Guest WiFi network, in the command line window, update the linux packages use: 'sudo apt-get update'

In the command line window, Type: 'python --version' + Enter, should return you the current python version installed. It might be Python 2.7, however, we have beening learning Python 3. We need to set the 'python alias' to be 'python 3.4' but not 'python 2.7'. Do as follows in the command line:

alias python='/usr/bin/python3.4'

After this setup, when you type 'python --version' in the command line window, you should see 'python 3.4' to be returned.

To open a '.py' file in 'vim' in the RPI linux system, you should use 'vi test.py' to open it. When you want to run the code in 'vi', you should do '! python3.4 %' instead of '! python %' as you did in the Windows OS.

3. Turn on an LED by running the program on the board:

1. Connect the USB cable of the keyboard and the mouse to the RPI Board.
2. Make sure the SD card is in the socket on the board.
3. Power up the board and just wait for a bit. You should see the Linux operating system desktop similar to this: (may have a different backgroud):

If you want to shut down the RPI board, please DO NOT directly plug-off the power cable. Go to the start menu and shut it down over there!!!

Click the Raspberry icon (the start menu) on the top-left corner of the view, select Programming - Python 3 (IDLE) to open the console.

To open an independent script file, select File - New File. In the new window, select File - Save As. Ust test.py as the file name and save it on the desktop of the linux system.

Open a linux terminal, install rpi.gpio package: (make sure you have the wifi connection):

According to the Pin Map of the PI board, connect BCM 23 to the resistor, and connect any of the GROUND pin to the cathode of the LED.
The Pin Map can be found below:

Before you connecct the LED to a GPIO pin, connect it as the shown in the following figure first to make sure your LED is working properly:
Please keep in mind that, the LONGer pin of the LED is the Anode, should be connected to the higher voltage end. The shorter pin of the LED should be connected to the resistor and then to the GND (0V) pin. The resistor can be 100 ohm - a few hundred ohms, it is just to project the LED getting burned by the current.

If the LED works fine, connecct the RED wire in the figure above to the BCM 23 pin on the RPI board.

Type the following code into your new script window and save it.

This will turn on Pin 23 permanently. A dead loop is bad, the PI will run this forever, which is power-consuming.

You can make the LED flash for a certain period of time and turn it off:
Modify the code:

Then, run this code at the Linux terminal:

>> sudo python test.py

The LED will be turned on for 1 second and then off. You can modify the number in the 'sleep()' function to change the delay time. It can be even 0.1s, or 0.01s, etc.

4. Toggle LED by a pushbutton on the GUI

We are going to use the 'tkinter' Class to build a simple GUI to toggle the LED connected to the RPI board. This is just the first time we run a GUI in Linux/RPI. In the future, we will use the 'PyQt' Class to build GUIs instead of using 'tkinter'.

Keep in mind that, the 'tkinter' Class is great and powerful. Work on this only may take you the entire semseter to learn and become a professional. 'PyQt' can do the similar job as 'tkinter' but PyQt is more popular and there are more job positions/postings asking for PyQt skills but not tkinter skills.. We don't have time to explore both so we'll pick up PyQt for our experiments.

Type the following code into a new script file, test_1.py, click Run in the menu.

A short demo video can be found below:

5. Push your code to GitHub and send me the link of the repository to the home work email. (You can directly push it to GitHub in the RPI environment, Linux has git and vi).

Tasks:

Follow the tutorial and repeat all the work I've done there. Demonstrate your work to me in class. Raise your hand when you are done for each task so I can check these boxes on my grade paper.

Section 1: 20 points
Section 2: 20 points
Section 3: 25 points
Section 4: 25 points
Section 5: 10 points

(There are no due dates for these demonstration tasks here and in the future. As long as you can get it done before the final exam, you'll be able to get the credit for these. You just need to demonstrate it to me in person).