raspberry

Control Arduino from Raspberry Pi with pyFirmata

Requirements
  1. Raspberry Pi with Raspbian OS installed in it
  2. Arduino Uno or any other Arduino board
  3. Arduino USB cable
  4. LED

 

Installing PyFirmata in Arduino using Raspberry Pi

To upload PyFirmata firmware in Arduino, we have to install Arduino IDE in Raspberry Pi. Follow these steps to install:

Step 1:- Connect the Raspberry Pi to the internet. Open command terminal and type the following command and hit enter

sudo apt-get -y install arduino python-serial mercurial

Wait for few minutes, it will take time. This command will install the Arduino IDE in your Raspberry Pi.

Step 2:- Now, we will install pyFirmata files using the given github:

git clone https://github.com/tino/pyFirmata

Then run the following command:

cd pyFirmata
sudo python setup.py install

Step 3:- We have installed all the required files and setups.

Now, connect your Arduino board with Raspberry Pi using USB cable and launch Arduino IDE by typing arduino in terminal window.

Step 4:- Then type lsusb command to check whether Arduino is connected with your raspberry pi.

In Arduino IDE, Go to tools and choose your board and Serial Port.

Step 5:- Upload the PyFirmata firmware on the Arduino by clicking File -> Examples ->  Firmata -> Standard Firmata and then click upload button . As shown below.

We have successfully installed the pyFirmata firmware in the Arduino board. Now, we can control our Arduino using Raspberry Pi.

For demonstration we will blink and fade an LED on the Arduino by writing python codes in Raspberry Pi.

 

 

Code Explanation

For coding part, you should read documentation of pyFirmata for better understanding. We will use pyFirmata functions to write our code. You can find pyFirmata documentation by following the link.

So let’s start writing the code

Open your favorite text editor on the Raspberry Pi and import pyFirmata library.

import pyfirmata

Define pin on the Arduino to connect the LED

led_pin = 9

Now, we have to write serial port name on which Arduino board is connected using pyfirmata.Arduino() function and then make an instance by assigning port in board variable.

board = pyfirmata.Arduino("/dev/ttyACM0")
print "Code is running”

In while loop, make led pin HIGH and low using board.digital[].write() function and give delay using board.pass_time() function.

while True:
    board.digital[led_pin].write(0)
    board.pass_time(1)        
    board.digital[led_pin].write(1)
    board.pass_time(1)

Our code is ready, save this code by putting .py extension to the file name.

Open command terminal and type python blink.py to run the code on the Arduino board. Make sure your Arduino board is connected with your Raspberry Pi board using USB cable.

Now, you can see Blinking LED on the Arduino board.

Complete code for blinking LED using pyFirmata is given at the end.

Fading LED on Arduino using pyFirmata

Now, we will write code for fading the LED to make you more familiar with the pyFirmata functions. This code is easy as previous one. You have to use two for loops, one for increase brightness and other for decrease brightness.

In this code, we have defined the pins in different way like led = board.get_pin(‘d:9:p’) where d means digital pin. This is function of pyFirmata library. Read the documentation for more details.

Complete code for Fading LED using pyFirmata is given at the end.

Now, you can add more sensors to your system and make it more cool, check our other Arduino projects and try building them using Raspberry pi and python script.

Code

Python code for LED blink:

import pyfirmata

led_pin = 9

board = pyfirmata.Arduino("/dev/ttyACM0")

while True:
board.digital[led_pin].write(0)
board.pass_time(1)
board.digital[led_pin].write(1)
board.pass_time(1)

Python code for Fading LED:

import time
import pyfirmata

delay = 0.3
brightness = 0

board = pyfirmata.Arduino("/dev/ttyACM0")

led = board.get_pin('d:9:p')
while True:
# increase
for i in range(0, 10):
brightness = brightness + 0.1
print "Setting brightness to %s" % brightness
led.write(brightness)
board.pass_time(delay)

# decrease
for i in range(0, 10):
print "Setting brightness to %s" % brightness
led.write(brightness)
brightness = brightness - 0.1
board.pass_time(delay)

Linux, Debian remove / stop service

To stop a service
sudo service servicename stop

To disable service autostart
sudo update-rc.d servicename disable

Raspberry turn off usb ports

download this

https://github.com/codazoda/hub-ctrl.c

You can control the power on a port using the following command. (I installed it in user bin directory)

sudo $HOME/bin/hub-ctrl -h 1 -P 2 -p 1

That says to control hub 3 (-h 3) port 1 (-P 1) and to turn the power off (-p 0). You can also use ”-p 1” to turn the power back on.

Raspberry: upload Arduino sketch from CLI

install these packages

sudo apt-get install arduino-core arduino-mk

Then add yourself to the dialout group to allow you to upload code to the Arduino board

sudo usermod -a -G dialout pi (Change pi to be your username if different)

Create Makefile

ARDUINO_DIR = /usr/share/arduino
BOARD_TAG = uno
ARDUINO_PORT = /dev/ttyACM*
ARDUINO_LIBS =
include /usr/share/arduino/Arduino.mk

to build

make

to upload

make upload

Crontab on Linux

To launch a program at reboot.

contab -e

Add following line to crontab file:

@reboot sudo python /home/pi/hw-home.py /home/pi/hw-home.txt