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
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
rm -r NAME
remove directory
rm NAME
remove file
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