Raspberry Pi Learning Resources Collection

Raspberry Pi Learning Resources Collection

Software and Tool Resources

• Official operating system download page

• SD card formatting software for Windows: SD Formatter

• [Operating system image writing tool for Windows](Win32 Disk Imager)

• Remote desktop access via VNC

Install tightvncserver on the Raspberry Pi, and install RealVNC on the computer.

• Remote desktop access via RDP (better performance than VNC)

Install xrdp on the Raspberry Pi, and use the mstsc command on Windows.

• Remote access to the Raspberry Pi via SSH. On Windows, available tools include PuTTY and [XSHELL](Products : Xshell 5)

• A useful open-source archive utility for Windows: [Bandizip](Download Free Zip Archiver to open ZIP, RAR, 7z files)

• Open-source FTP server and client software: [FileZilla](The free FTP solution)

• Domestic PyPI mirror from Douban. Add the suffix after the pip command, for example: pip install pygame -i Simple Index

Raspberry Pi Operation and Usage

• Configuration file

/boot/config.txt

• IP address configuration file

/etc/network/interfaces

• DHCP configuration files (if using a static IP, clear them with the following command)

sudo rm /var/lib/dhcp/*

• Hostname/network name configuration file

/etc/hosts

• Configuration command

sudo raspi-config

• Take a photo with the camera

rapistill -o xxx.jpg

• Record video with the camera (ms)

raspivid -o video.h264 -t 10000

• Use the Raspberry Pi as a network-attached storage server

sudo apt-get install samba

sudo apt-get install samba-common-bin

Add a Samba user:

sudo smbpasswd -a xxx

Modify the workgroup on the first line of /etc/samba/smb.conf

Add the following at the bottom:

[USB]
path=/media/NAS
comment= NAS driver
valid users=xxx
writeable=yes
browseable=yes
create mask=0777
public=yes

Restart Samba.

• Network print server: CUPS

sudo apt-get install cups

sudo usermod -a -G lpadmin xxx

Install a browser for web-based management, using port 631:

sudo apt-get install iceweasel

Management interface

• Screenshot tool: scrot

sudo apt-get install scrot

• Delayed screenshot

scrot -d 5

• Interactive mouse selection screenshot

scrot -s

• I2C communication tools

sudo apt-get install i2c-tools

sudo i2cdetect -y 1 // for older versions, change 1 to 0

• Serial port monitoring tool: minicom

sudo apt-get install minicom

minicom -b 9600 -o -D /dev/ttyAMA0

First enable local echo to see feedback: Ctrl+A, Z, E

Raspberry Pi Hardware

• Safety guidelines

• Voltage on GPIO pins must not exceed 3.3V

• Output current per pin must not exceed 3mA

• Power supply voltage must not exceed 5V

• Total output current of the 5V supply should not exceed 250mA

• The simplest voltage conversion method is to use a resistor divider with 470 ohms and 220 ohms in series. You can also scale this proportionally to 47k and 22k to reduce current loss.

• GPIO output capability summary reference article

• Raspberry Pi accessories

• Raspberry Squid, an accessory with built-in resistors, LEDs, and buttons. Includes a Python squid library.

• You can use the motor driver RasPiRobot Board to power the Raspberry Pi. The motor driver board Python library is raspirobotboard.

• Sensor interface board [SenseHAT], with Python libraries such as sense-hat, SenseHAT, and explorerhat

• [Compute Module](Raspberry Pi Compute Module: new product! - Raspberry Pi)

• Pi Plate prototyping board for soldering components and rapid development

• You can design your own prototype board that complies with the HAT standard. Enable dtparam=i2cvc=on in the config file, and use the EEPROM flashing tool

• Raspberry Pi HAT hardware design guide

• AC power switching accessory: PowerSwitch Tail II (opto-isolator + relay module)

• For precise servo motor control, you can use the Servo Blaster library

• To control multiple servo motors at the same time, you can use Adafruit's servo motor HAT (Hardware Attached on Top), see the Adafruit documentation

• To control DC motors, you can build an H-bridge using a chip such as the L293D, or use an H-bridge module from SparkFun

• To control stepper motors, you can use RaspiRobot

• To detect motion, you can use a passive infrared motion detector (PIR)

• To measure resistance, you can connect a capacitor and estimate the value by measuring the capacitor charging time

• The Raspberry Pi does not have built-in analog input. Analog signal acquisition can be implemented using an ADC module such as the MCP3008

• For temperature measurement, you can use the less accurate TMP36 or the high-precision digital temperature sensor DS18B20

• For measuring temperature, humidity, and air pressure, use the [Sense HAT](API Reference - Sense HAT)

• The aLaMode board (an Arduino platform with GPIO interface). Due to a design flaw in aLaMode, you need to wrap a little insulating tape around the Raspberry Pi Ethernet port.

• Videos on Raspberry Pi hardware control

Quick Uses for Raspberry Pi

• Media center: install the OpenELEC_Pi2 system and use [Kodi](Official Kodi Wiki)

• Office software: abiword, gnumeric

• Browser: chromium-browser

• Webcam server: install motion

• Configuration

sudo vim /etc/motion/motion.conf
# change daemon off to on
# change webcam_localhost=on to off

sudo vim /etc/default/motion
# change sart_motion_daemon=no to yes

• Start it with: service motion start

• Run classic emulator games: install stella

• Install JDK and run Minecraft (this software is already installed on Raspberry Pi 3)

sudo apt-get install openjdk7-jkd(you may need to update to version 8)
wget http://getspigot.org/spigot18/spigot_server.jar
java -Xms512M -Xmx800M -jar spigot_server.jar nogui
# sudo vim eula.txt
# change eula=false to true

• Run the game [Open Arena](OpenArena EX - オープンアリーナ) (very violent)

• FM transmitter: install the pifm library. Attach a short wire to GPIO pin 4 as an antenna.

mkdir pifm
cd pifm
wget http://www.icrobotics.co.uk/wiki/imagies/c/c3/Pifm.tar.gz
tar -xzf Pifm.tar.gz
sudo ./pifm sound.wav 103.0  # audio file and frequency to play

• Image processing: GIMP

sudo apt-get install gimp

• Listen to internet radio: vlc

• GPS modules: gpsd and gpsd-clients, commands: cgps -s, xgps

• To communicate with Arduino, you can use pyserial over serial, or install PyFirmata firmware on the Arduino

Linux Command Reference

• View IP address

ifconfig (this command is already outdated in the book)

ip a

• Run a script automatically at system startup

Modify /etc/rc.local

Add something like this on the first line:

/user/bin python /home/pi/my_program.py &

The & symbol means run in the background. Otherwise, the system may fail to boot into the desktop properly. Very important.

• Make a script run automatically

/etc/init.d/my_server (my_server is a custom script file)

sudo chmod +x /etc/init.d/my_server (add execution permission)

• Run scripts periodically: crontab -e

• Search files: find /home/pi (starting directory) -name abc.py

• View command history: history !x (execute the x-th command in history)

• List USB devices: lsusb

• Redirect command output to a file: ls > abc.txt

• Concatenate files: cat a.txt b.txt > c.txt

• Pipes and regular expressions: ls *.py | grep Jun

• Suppress output: ls > /dev/null

• Run in background: abc.py &, bring back to foreground with fg

• Alias: alias l='ls -a'

• Apply changes to a file immediately: source .bashrc

• Change system time: sudo date 010203042031 (MMDDHHMMYYYY)

• Disk space: df -h

Python Computer Vision

• Install SimpleCV

sudo apt-get update
sudo apt-get install ipython python-opencv python-scipy
sudo apt-get install python-numpy python-setuptools python-pip
sudo pip install svgwrite
sudo pip install https://github.com/sightmachine/SimpleCV/zipball/master
Run SimpleCV

• Example program using Python and the Raspberry Pi camera

import picamera
from SimpleCV import *

def get_camera_image():
    with picamera.PiCamera() as camera:
        camera.resolution = (1024, 768)
        camera.awb_mode = 'off'
        camera.capture('tmp.jpg')
        return Image('tmp.jpg')

• Python [picamera](picamera - Picamera 1.13 Documentation) documentation

• Edge detection. Parameters: Canny edge detection, thresh determines the required edge length, distance is the distance between circles.

SimpleCV:1> c=Camera()
SimpleCV:2> i=c.getImage()
SimpleCV:3> i.show  - best i source and related information.()
SimpleCV:4> i2=i.invert()
SimpleCV:5> i2.show()
SimpleCV:6> coins=i2.findCircle(canny=100,thresh=70,distance=15)
SimpleCV:7> coins
SimpleCV:8> coins.draw(width=4)
SimpleCV:9> coins.show()

from SimpleCV import *

c = Camera()
while True:
    i = c.getImage().invert()
    coins = i.findCircle(canny=100, thresh=70, distance=1)
    print(len(coins))

• Face detection: findHaarFeatures Haar feature reference

• Motion detection: blob detection, findBlobs

• Optical character recognition (OCR): install tesseract

• To control LEDs with as few pins as possible, you can use [Charlieplexing](Charlieplexing - Wikipedia)

Python Control of Raspberry Pi Hardware

• Turn an LED on and off. Python needs superuser privileges to call the RPi.GPIO library, so run it with sudo python led_blink.py

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.OUT)

try:
    while True:
        GPIO.output(18, True)
        time.sleep(0.5)
        GPIO.output(18, False)
        time.sleep(0.5)
finally:
    GPIO.cleanup()  # safety mode: reset GPIO pins to input state to avoid short circuits

• PWM output

import RPi.GPIO as GPIO

led_pin = 18
GPIO.setmode(GPIO.BCM)
GPIO.setup(led_pin, GPIO.OUT)
pwm_led = GPIO.PWM(led_pin, 500)
pwm_led.start(100)

while True:
    duty_s = input("Brightness input (0-100):")
    duty = int(duty_s)
    pwm_led.ChangeDutyCycle(duty)

• PWM control program with GUI

from tkinter import *
import RPi.GPIO as GPIO
import time

led_pin = 18
GPIO.setmode(GPIO.BCM)
GPIO.setup(led_pin, GPIO.OUT)

class App:
    def __init__(self, master):
        frame = Frame(master)
        frame.pack()
        self.check_var = BooleanVar()
        check = Checkbutton(
            frame,
            text='Pin 18',
            command=self.update,
            variable=self.check_var,
            onvalue=True,
            offvalue=False
        )
        check.grid(row=1)

    def update(self):
        GPIO.output(led_pin, self.check_var.get())

root = Tk()
root.wm_title('On/Off Switch')
app = App(root)
root.geometry("200x50+0+0")
root.mainloop()

• PWM output

import RPi.GPIO as GPIO
import time

led_pin = 18
GPIO.setmode(GPIO.BCM)

# callback function
def my_callback(channel):
    print('You pressed the button')

GPIO.setup(led_pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

# bouncetime is the GPIO library's built-in debounce feature
GPIO.add_event_detect(led_pin, GPIO.FALLING, callback=my_callback, bouncetime=100)

i = 0
while True:
    i = i + 1
    print(i)
    time.sleep(1)

• Use RaspiRobot to control a bipolar stepper motor

from rrb3 import *
import time

rr = RRB3(12.0, 12.0)  # battery, motor

try:
    while True:
        delay = input("Delay milliseconds between steps:")
        steps = input("How many steps forward?")
        rr.step_forward(int(delay) / 1000.0, int(steps))
        steps = input("How many steps backward?")
        rr.step_reverse(int(delay) / 1000.0, int(steps))
finally:
    GPIO.cleanup()

• Use pygame to detect keyboard and mouse movement

import pygame
import sys
from pygame.locals import *

pygame.init()
screen = pygame.display.set_mode((640, 480))
pygame.mouse.set_visible(0)