2010910 pi workshop notes

Intro

Raspberry Pi 3 computer
OS (Raspbian) loaded on SD card
All GPIO pins are flexible 3.3V OUT or IN (will generate floating voltage when not programmed)
GPIO can be programmed using gpio utility: http://wiring.com/the-gpio-utility/
UART pins carry data (RX=receive, TX=transmit), allows connection of devices (GPS), 3V->3V, GND->GDN, RX->TX, TX->RX
Sends text signals, each character encoded in 8bits ("packed" encapsulated into a "start bit" and a "stop bit")
Speed is 9600 Baud (1 Baud = 1 bit per sec)
To access this data, you can either use a Python script, or a software called "screen"
directory "/dev/ttyACM0 9600" contains a new file that represents the connexion to a device (arduino, printer, etc.)
I2C protocol
For example: BMP280 sensor temperature and pressure sensor (4pins=3V, GND, SDA, SCL)
On pi, up to 127 sensors can be connected to the SDA and SCL ports. Each device has a fix-programmed specific address.
i2c-tools is a program that allows to detect from all these sensors using the i2cdetect protocol.
"sudo raspi-config" to configure the pi computer
Step 1. Tell pin to be GPIO2
Step 2. Tell pin to be ON or OFF
2 ways of accessing the pins: GPIO# or pin#
"GPIO-g" flags to GPIO#

First test

If we want to connect the LED on the GPIO4 port:

Controlling GPIO ports using Python:

Or using BASH (Shell) command line (UNIX language):
sudo -i
echo "4" > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio4/direction
echo "1" > /sys/class/gpio/gpio4/value <-turns it on
echo "0" > /sys/class/gpio/gpio4/value <-turns it off

Or GPIO utility command:
gpio -g mode 4 out
gpio -g write 4 1 <-turns it on
gpio -g write 4 0 <-turns it off

The Operating System

An OS is a piece of software that people wrote to use a computer in an easy and structured way.
Linus is the kernel (not an operating system), robust, versatile, stable.
Operating system is Raspian in our case.

Linux always has a BASH (Shell) terminal: type something, press enter, view output.

The terminal uses: arrows
enter key (execute)
tab key (autocomplete)

Everything in Linux is either a FILE or a DIRECTORY

"man" stands for manual and gives instructions on how to use commands, eg. "man cat" "pwd" shows the directory we're in
"ls" lists all items in this directory
"ls -ailh" give the size of all files in the directory

"ctrl c" cancels all commands
"ctrl l" cleans the screen

"sudo -s" login as root
"exit" leaves root mode

"cat [file name] | less" -> the pipe character "|" will take the output of one command into the next command

Bash scripting

==test1:==

nano myfirstscript.txt

#! /bin/bash"
echo Hello!
echo World!
whoami

chmod +x myfirstscript.txt

->makes the file executable -> into some program that you can run

./myfirstscript.txt

-> executes the file

==test2:==

nano mysecondscript.txt

--

#! /bin/bash
echo Hello!
echo World!
whoami

mkdir woz
touch woz/niak.txt

--

chmod +x mysecondscript.txt

./mysecondscript.txt