Wednesday, January 31st, 7PM, Dallas Makerspace
Pi GPIO Library & pigs
* How to start the pigpiod service/daemon
* Use the command line tool, "pigs", to turn on/ turn off LEDs
* Use "pigs" command to continuously flash LEDs (PWM)
* Write a simple C/C++ program to turn on/ turn off LEDs using pigpio C library.
* Write a simple Python program to turn on / turn off LEDs using pigpio Python library.
* How to stop the pigpiod service/daemon

What to Bring:
Raspberry Pi (recommend Rraspberry Pi 3)
8/16/32 GB uSD card, Class 10, for your Pi's OS - please bring a working/running Pi!
USB Power Supply for Pi (recommend 5.1V, 2.5A or 3.0A)
Keyboard, Mouse, Monitor, and cables to hook up the Raspberry Pi
Laptop, USB to uSD adapter to program the uSD card from the laptop.

Pi Gpio Daemon, pigpiod
Start the daemon:
$ sudo pigpiod

Stop the daemon:
$ sudo pigpiod ??? ---- Couldn't find a way to "gently ask" pigpiod to unload

This will work:
$ sudo killall pigpiod

Add pigpiod to auto-start using crontab:
Determine the path to the pigpiod executable (Need this later)
$ whereis pigpiod

Bring up the crontab editor..
$ sudo crontab -e

Add the following line at the end of the crontab list
@reboot /usr/local/bin/pigpiod

Use ctrl-o to return
Use ctrl-x to exit

Add pigpiod as a service
$ sudo systemctl enable pigpiod.service

Disable pigpiod service: (not sure about this one...)
$ sudo systemctl disable pigpiod

If you see this:
"Can't lock /var/run/pigpio.pid"
The pigpiod daemon is already running

PIGS
The "pigs" command supports a whole host of functionality, providing a command line interface into the PiGPIO library.
The "pigs" command requires the pigpiod daemon running!
$ sudo pigpiod

GPIO Control
Turn on LED connected to GPIO18 with the following command:
$ pigs w 18 1

Turn off the LED:
$ pigs w 18 0

Delays
If you want pigs to delay 100ms:
$ pigs mils 100

Delay 100us
$ pigs mics 100

Combine multiple commands on a single line (pigs knows how many parameters to parse for each command)
Turn the LED on, wait 1000ms, turn the LED off:
$ pigs w 18 1 mils 1000 w 18 0

Hardware PWM
Configure GPIO18 as PWM output, 10Htz, 50% duty cycle (add four zeros after the percent value)
$ pigs hp 18 10 500000

Configure GPIO18 as PWM output, 2Htz, 50% duty cycle (add four zeros after the percent value)
$ pigs hp 18 2 500000

Create command line bash script:
(This example is from the bottom of the "pigs" man page)
for ((i=0; i<10;i++)); do pigs w 18 1 mils 100 w 18 0 mils 100; done

Create a small PIGS script:
Sorry... I didn't get this working...
$ pigs tag 100 w 18 1 mils 100 w 18 0 mils 100 jmp 100

Resources:
C++ example using PiGPIO library
Script file to build above example
Python example reading a GPIO
Python example writing a GPIO
PiGPIO pdf



Side topic: One Wire Bus
One Wire Bus - Initiate device tree overlay search for one wire bus on gpio 18
$ sudo dtoverlay w1-gpio gpiopin=18 pullup=0

Typically, a 4.7K ohm resistor is used to pullup the single wire bus to 3.3V

If successful, list the one wire devices:
$ ls /sys/bus/w1/devices

1-Wire Bus example

E-mail me: jim@merkles.com.