RASPBERRY PI LINUX LESSON: From 16th to 28th

Raspberry Pi Linux LESSON 16: Search Inside Files with Grep

 

 

 no mazda

 

 -r

means recursively

 

  

all three command dont get "Chevy", because grep is case sensitive

what if we want case insensitive search?

 

find all "Ch" in every file under home folder, but get to many files. What happened?

 because we have a lot of invisible folders and files

 

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Raspberry PI Linux LESSON 17: Finding the Raspberry Pi IP Address 

 

 ping yourself

 

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 LESSON 18: Remotely Connect from Windows with Putty SSH Telnet Client

 

 

 

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 LESSON 19: Adding New Users

 first see how many users we have?

only one user "pi"

-m : make directory for him

-s: he's going to use bin

 

 becomes austin now, and see some welcome words here

 

what if austin wants to use davis' folder?

 

 also, austin can't delete davis as an account

 

 
succeed copy files from other users

 

 return to "pi"

 

 delete austin and davis, but with a "-r", the user's folder will also be deleted

 

 

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 LESSON 20: Backing Up your SD Card and Operating System

 

 remove the SD card

 

 

 

backup

 

 load system from backup

 

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 LESSON 21: Create a New admin User Like Pi

 

how to make paul like "pi"?

now paul has the privilege 

 

 

 

 

now paul is exactly like "pi"

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 LESSON 22: Understanding Linux File and Folder Permissions

start with "-"  -> files

with "d" -> folder

 

 r  -> read

w -> write

x -> excute

here, txt files are not excutable

xxx,yyy,zzz

x: owner

y: part of group that owns it

z: anyone else

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 LESSON 23: How to Change File Permissions

 

 

 

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 LESSON 24: Running Python on the Raspberry Pi

 

 

 

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 LESSON 25: GPIO Pinout for the Raspberry Pi 2

left and right most are BCM number scheme

Two central columns are BOARD number scheme

 

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 LESSON 26: Controlling the Raspberry Pi GPIO pins from Python

 

 

 

if you dont have the library, exit and:

sudo apt-get update

sudo apt-get upgrade

 GPIO.BOARD is the normal scheme of pin number

 

 

 True = 1

 False = 0

 

 clean all the pin setting. A good epilogue

 

 

 

 light: ON-OFF-ON-OFF

Use BCM number scheme to control pin 11

 

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LESSON 27: PWM Output on GPIO Pins from Python

voltage line drops down on oscilloscope screen

 set PWM(11,100)

100 means the cycle is 10 ms

start(50) means half the cycle has high voltage

 

 ChangeDutyCycle(??) :

change the started propotion of high voltage to  10% and 90%

 

  

 

 change frequency set on the first step

 

 

import RPi.GPIO as g
g.setmode(g.BOARD)
red = 11
g.setup(red,g.OUTPUT)
my_pwm = g.PWM(red,100)
my_pwm.start(0)
while(1):
        bright = input("How bright do you want?") #0-100
        my_pwm.ChangeDutyCycle(bright)

my_pwm.stop()
g.cleanup()

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 LESSON 28. Controlling a Servo with Raspberry Pi and Python

 

raspberry pi can only put out so much current.

if you hook a big old servo to your rasp that wants more current than what your rasp can produce, you can actually damage your rasp.

 if you are not sure, connect your input wires to an external 5v rasp output pin.

 

 here, black is ground, yellow is control, red is power

 in arduino, it's super easy to control servo, with writeAngle(...)

 but in rasp, you have to know more:

 

ok, let's do some experiments!

import RPi.GPIO as g
g.setmode(g.BOARD)
g.setup(11,g.OUT)
pwm = g.OWM(11,50)
pwm.start(5)
pwm.ChangeDutyCycle(2)
pwm.ChargeDutyCycle(12)
pwm.stop()
g.cleanup()

 

  

import RPi.GPIO as g
g.setmode(g.BOARD)
g.setup(11,OUTPUT)
pwm = g.PWM(11,50)
pwm.start(7)
for i in range(20):
        desiredPosition = input("Where do you wan the servo to be 0-180?")
        DC =  desiredPosition/18 + 2
        pwm.ChangeDutyCycle(DC)
pwm.stop()
g.cleanup()

 recurrently rotate from 0-180° and 180-0°

import RPi.GPIO as g
import time
g.setmode(g.BOARD)
g.setup(11,OUTPUT)
pwm = g.PWM(11,50)
pwm.start(7)
while(1):
        for i in range(180):
                DC =  i/18 + 2
                pwm.ChangeDutyCycle(DC)
                time.sleep(0.02) # use 0.05 makes servo slower
        for i in range(180,0,-1):
                DC =  i/18 + 2
                pwm.ChangeDutyCycle(DC)
                time.sleep(0.02)
pwm.stop()
g.cleanup()