PyFirmata summary

For using a firmata (Respberry <-> Arduino) you must install it on:

• Arduino (Firmata - Arduino)
• Raspberry Pi (Firmata - Raspberry Pi)

Statement of connection types:

device/connection type	get_pin(...) string	available values
relay shield	d:pin_no:o	0 and 1
DC motor	d:pin_no:p	0.0 - 1.0
servo	d:pin_no:s	0 - 255
analog input (*)	a:pin_no:i	0.0 - 1.0

(*) you must start reading analog input:

from pyfirmata.util import Iterator
...
board = ArduinoMega('/dev/ttyUSB0')
iterator = Iterator(board)
iterator.start()
...

Example use servo:

from pyfirmata import ArduinoMega
board = ArduinoMega('/dev/ttyUSB0') # Arduino usb port
servo = board.get_pin('d:2:s')      # pin PWM no 2
servo.write(50)                     # set servo position 0-255

Temperature sensor LM35

We need:

• Arduino with firmata library (Firmata - Arduino)
• Raspberry Pi with python and firmata package (Firmata - Raspberry Pi)
• Temperature sensor LM35 (specification: http://www.ti.com.cn/cn/lit/ds/symlink/lm35.pdf)

Sensor LM35:

Connections schema:

We can connect LM35 to 5V or 3.3V, it doesn't matter.


Photo from my LM35 connections:

Example python app lm35_test.py:

from pyfirmata import ArduinoMega
from pyfirmata.util import Iterator
import time

board = ArduinoMega('/dev/ttyUSB0') # connect to arduino usb port

iterator = Iterator(board) # start reading analog input
iterator.start()

pinTemp = board.get_pin('a:0:i') # set valid in analog pin

while True:
    voltage = pinTemp.read() # read voltage input
    if voltage is not None: # first read after startup is somtimes None
        temp = 5.0*100*voltage # convert voltage to temperature
        print "{0} Celsius".format(temp)
        time.sleep(1) # 1 second waiting 

Run python environment (see Firmata - Raspberry Pi (part 2)), for example:

# cd robot/python_firmata_test/
# source bin/activate

and run app:

# python2.7 lm35_test.py

Screenshoot form app:

LM35 is theoretically appropriately calibrated but in my opinion, given the temperature is overestimated by about 2-4 degrees Celsius. I had a reference (room thermometer;) ) thermometer.

links:
http://raspberrypi-aa.github.io/session3/firmata.html
http://www.ladyada.net/learn/sensors/temp36.html
http://www.ti.com.cn/cn/lit/ds/symlink/lm35.pdf

Relay shield control

We need:

• Arduino with firmata library (Firmata - Arduino)
• Raspberry Pi with python and firmata package (Firmata - Raspberry Pi)
• relay shield

Relay shield:

Connections schema:

Photo from my relay shield connections:

Simple app to blinking relay connect to 22 pin:

from pyfirmata import ArduinoMega, time
board = ArduinoMega('/dev/ttyUSB0')
servoA = board.get_pin('d:22:o')

while True:
   servoA.write(1) 
   time.sleep(1)
   servoA.write(0) 
   time.sleep(1)

Command line completely app relay_example.py:

from pyfirmata import ArduinoMega, time
board = ArduinoMega('/dev/ttyUSB0')
firstPin = 22 # number first pin, app use 8 pins

__copyright__ = "Copyright 2014, http://letsmakearobot.blogspot.com/"
__version__ = "0.1.0"
__license__ = "GPL"
__email__ = "sebastian.dziak@gmail.com"

def info():
    print "------------------------------------------------"
    print "Command parameters:"
    print "  1-8 - relay no"
    print "  0-1 - relay status (0 - off, 1 - on)"
    print "  ...and exit from app: exit"
    print 
    print "Examples:"
    print "  2 1 #set on relay no 2"
    print "  2 0 #set off relay no 2"
    print "  5 1 #set off realy no 5 "
    print "  exit"
    print "------------------------------------------------"

def validate(position):
   if not position is None and (float(position)<0 or float(position)>255):
      return "Invalid parameter!"

info()

pins = []
for n in range (0, 8):
   pinNo = firstPin + n
   pins.append( board.get_pin('d:'+str(pinNo)+':o') )

while True:
   cmdLine = raw_input('Relay_no(1-8) set_status(0-1):')
   if cmdLine == 'exit': break 
   args = cmdLine.split()
   pins[int(args[0])-1].write(int(args[1]))

print "goodbye"

Run python environment (see Firmata - Raspberry Pi (part 2)), for example:

# cd robot/python_firmata_test/
# source bin/activate

and run app:

# python2.7 relay_example.py

Screenshoot form app:

Servo control

Introduction

A robot to be able to participate in the interaction with the environment should use the servos. We can control the servo using PWM outputs.

We need:

• Arduino with firmata library (Firmata - Arduino)
• Raspberry Pi with python and firmata package (Firmata - Raspberry Pi)
• servo, can be very cheap (eg. TG9)
• additional DC supply or battery, voltage should be adjusted to the servo

Servo connection

In scheme we need additional supply DC. It's very important! Servo gets high current, which can not provide the power arduino (in our case the usb Raspebrry).
DC supply voltage must be matched to the voltage servo. Most servos working with voltages 4.8 - 6.0V.

Schema

Breadboard

and photo from my real connections:

I replaced the batteries DC power supply.

Software

Access to the servo with python:

from pyfirmata import ArduinoMega
board = ArduinoMega('/dev/ttyUSB0')#usb port
servo = board.get_pin('d:2:s')     #pin PWM no 2 (depending
servo.write(50)                    #set servo position 0-255

Below I put the program to command line control the servo. Should focus on two lines, one:

board = ArduinoMega('/dev/ttyUSB0') # usb port

If necessary, change the port that is connected to the Arduino.
second:

servo = board.get_pin('d:2:s') # pin PWN no 2

where:

d - digital output (not change)
2 - number PWM pin to connect the servo
s - servo control. This is very important! If you set the "p" (power) can damage the servo!

Sample app to command line control the servo:

from pyfirmata import ArduinoMega, time
board = ArduinoMega('/dev/ttyUSB0') # usb port
servo = board.get_pin('d:2:s') # pin PWM no 2

__copyright__ = "Copyright 2014, http://letsmakearobot.blogspot.com/"
__version__ = "0.1.0"
__license__ = "GPL"
__email__ = "sebastian.dziak@gmail.com"

def info():
    print "------------------------------------------------"
    print "Command parameters:"
    print "  0-255 - sevo position"
    print "  ...and exit from app: exit"
    print
    print "Examples:"
    print "  25"
    print "  120"
    print "  exit"
    print "------------------------------------------------"

def validate(position):
   if not position is None and (float(position)<0 or float(position)>255):
      return "Invalid parameter!"

info()
while True:
   value = raw_input('Position (0-255):')
   if value == 'exit': break  
   resp = validate(value)
   if resp is None:
      servo.write(float(value))
   else:
      print resp
 
print "goodbye"

links:
http://arduino.cc/en/Tutorial/sweep
http://www.robotoid.com/appnotes/arduino-operating-two-servos.html

DC motor controller

Introduciton

A robot must have a possibility to move. One of the simplest solutions is to use a tracked chassis propelled by two engines. Two DC motors working allows for forward movement, one motor or two in differnet directions - turn left/right.

We need

• L298N coontroller
• Arduino with firmata library
• Raspberry Pi with python and firmata package
• two DC motors for test (probably we will use other engines to drive the robot)

Motor drive controller with L298N module

L298N DC motors controller specification:

• operating voltage <48V
• 2A per channel
• the maximum 20W power at 75 °C
• supply current 36mA circuit  
• operating temperature:-20C +135 C
• dimensions 44mm x 44mm x 27mm

I took the diagram from  http://www.funnyrobotics.com/2011/03/arduino-with-l298n-based-dual-motor.html

and my test connections:

my application to control motors (motor_test.py):

from pyfirmata import ArduinoMega
board = ArduinoMega('/dev/ttyUSB0')

__copyright__ = "Copyright 2014, http://letsmakearobot.blogspot.com/"
__version__ = "0.2.0"
__license__ = "GPL"
__email___ = "sebastian.dziak@gmail.com"

pin_motor_A_L = board.get_pin('d:4:p')
pin_motor_A_R = board.get_pin('d:5:p')
pin_motor_B_R = board.get_pin('d:6:p')
pin_motor_B_L = board.get_pin('d:7:p')

cmd_motor = ('A','B')
cmd_direction = ('L','R','S')
invalid_number_parameters = "Invalid number of parameters!"
invalid_parameter = "Invalid parameter: "

def set_motor(motor, cmd, speed):
    if args[0]=='A':
        if cmd=='S':
        pin_motor_A_L.write(0)  
        pin_motor_A_R.write(0)  
        elif cmd=='L':
        pin_motor_A_R.write(0)             
        pin_motor_A_L.write(speed)  
        elif cmd=='R':
        pin_motor_A_L.write(0)  
        pin_motor_A_R.write(speed)  

    if args[0]=='B':
        if cmd=='S':
        pin_motor_B_L.write(0)  
        pin_motor_B_R.write(0)  
        elif cmd=='L':
        pin_motor_B_R.write(0)             
        pin_motor_B_L.write(speed)  
        elif cmd=='R':
        pin_motor_B_L.write(0)  
        pin_motor_B_R.write(speed)  

   
def info():
    print "------------------------------------------------"
    print "Command parameters:"
    print "  A,B - motor id"
    print "  L,R,S - L - left rotation, R - right rotation, S - motor stop"
    print "  0.0-1.0 - velocity (should be given only with the option of L or R)"
    print "  ...and exit from app: exit"
    print   
    print "Examples:"
    print "  A R 0.4"
    print "  A S"
    print "------------------------------------------------"

def validate(engine, cmd, speed):
    if engine not in cmd_motor:
        return invalid_parameter+engine
    elif cmd not in cmd_direction:
        return invalid_parameter+cmd
    elif cmd=='S' and not speed is None:
        return invalid_number_parameters
    elif (cmd=='L' or cmd=='R') and speed is None:
        return invalid_number_parameters
    elif not speed is None and (float(speed)<0.0 or float(speed)>1.0):
         return invalid_parameter+speed

info()
while True:
    cmdLine = raw_input('CMD (A/B L/R/S 0.0-1.0):')
    if cmdLine == 'exit': break    

    args = cmdLine.split() 

    if len(args)>0:    
        engine = args[0]
    else:
        engine = None

    if len(args)>1:    
        cmd = args[1]
    else:
        cmd = None
    
    if len(args)>2:    
    speed = float(args[2])
    else:
    speed = None       

    resp = validate(engine, cmd, speed)

    if resp is None:
    set_motor(engine, cmd, speed)
    else:
    print resp

print "goodbye"

links:
http://arduino-info.wikispaces.com/MotorDrivers
http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00000240.pdf
http://www.funnyrobotics.com/2011/03/arduino-with-l298n-based-dual-motor.html 
http://en.wikipedia.org/wiki/Phase-locked_loop

Speech synthesizer

We need

• Raspberry Pi with ArchLinux
• Sound output devices connected to mini-jack. I use amplituner with spekares. For tests we can use computer speakers or headphone.

 

Base sound software

Install:

# pacman -Sy alsa-utils alsa-plugins

call sound test:

# speaker-test -c 2

We should hear the test sound.

Festival synthesizer

Install Festival synthesizer:

# pacman -Sy festival festival-english

call Festival test from command line:

# echo "Hello Dave" | festival --tts

We should hear sound "Hello Dave".

Next step, we call Festival from Python code (is useful in the future). If it does not exist, create a directory

# mkdir robot   

create Python enviroment:

# cd robot/
# virtualenv2 --no-site-packages python_festival_test
# cd python_festival_test/
# source bin/activate

create file festivalTest.py:

import subprocess
text = '"Hello Dave"'
subprocess.call('echo '+text+'|festival --tts', shell=True)

call script:

# python2.7 festivalTest.py

We should hear sound "Hello Dave".

Additional

Install command line mp3 player:

# pacman -Sy mpg123

and play mp3 file:

# mpg123 example_file.mp3

Sound volume, check status:

# amixer

example response:

Simple mixer control 'PCM',0
  Capabilities: pvolume pvolume-joined pswitch pswitch-joined
  Playback channels: Mono
  Limits: Playback -10239 - 400
  Mono: Playback 40 [97%] [0.40dB] [on]

change volume:

# amixer cset numid=1 -- $sound_volume

where:
$sound_volume - is number beetwen -10239 and 400
numid - output: 0=auto, 1=analog, 2=hdmi




links:
https://wiki.archlinux.org/index.php/Advanced_Linux_Sound_Architecture
http://www.correderajorge.es/can-your-raspberry-pi-talk-2/
http://machakux.appspot.com/blog/44003/making_speech_with_python
http://www.raspberrypi-spy.co.uk/2013/06/raspberry-pi-command-line-audio/
http://www.imdb.com/character/ch0002900/quotes

RaPi Camera video streaming

We need

Raspberry Pi with ArchLinux and configured RaPi Camera.

Compile and run mjpg-streamer

install packages:

# pacman -Sy git gcc make cmake libjpeg-turbo

download and compile mjpg-streamer:

# cd /opt
# mkdir mjpg-streamer
# git clone https://github.com/jacksonliam/mjpg-streamer.git ./mjpg-streamer
# cd mjpg-streamer/mjpg-streamer-experimental
# make clean all

create run.sh file:

#!/bin/bash
LD_LIBRARY_PATH=/opt/mjpg-streamer/mjpg-streamer-experimental/ /opt/mjpg-streamer/mjpg-streamer-experimental/mjpg_streamer -i "input_
raspicam.so -fps 15 -q 50 -x 640 -y 480" -o "output_http.so -p 9000 -w /opt/mjpg-streamer/mjpg-streamer-experimental/www" &

add execution privileges:

# chmod +x run.sh

streaming test:

# ./run.sh

Camera LED should light up. Open in http browser url http://you_raspberry_address:9000/stream.html

We should see something like:

Autorun streaming  script

Create file /etc/systemd/system/mjpg-streamer.service:

[Unit]
Description=mjpg-streamer for robot

[Install]
WantedBy=multi-user.target

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/opt/mjpg-streamer/mjpg-streamer-experimental/run.sh
WorkingDirectory=/opt/mjpg-streamer/mjpg-streamer-experimental

and call commands:

#systemctl start mjpg-streamer
#systemctl enable mjpg-streamer

Final test

Reboot Raspberry and call in browser http://you_raspberry_address:9000/stream.html



links:
http://www.miguelmota.com/blog/raspberry-pi-camera-board-video-streaming/
http://blog.miguelgrinberg.com/post/stream-video-from-the-raspberry-pi-camera-to-web-browsers-even-on-ios-and-android/page/2
http://blog.miguelgrinberg.com/post/how-to-build-and-run-mjpg-streamer-on-the-raspberry-pi
https://wiki.archlinux.org/index.php/Systemd
http://grammarofdev.blogspot.com/2013/11/autorun-startup-script-on-raspberry-pi.html

Install RaPi Camera

Introduction

A good idea for remote control robot is a preview video. Raspberry Pi can connect to a dedicated high-quality camera.

We need

• Raspberry Pi with ArchLinux
• Raspberry Pi Camera (operating in the visible light) or Raspberry Pi NOIR (operating in the infrared)

  Raspberry Pi Camera, first (green shield) for the visible light, second (black) for the infrared.

Camera connection

Camera package includes ribbon cable. The free cable end should be connected to the Raspberry.

The cable you need to insert the appropriate side, blue side is to be directed toward the ethernet port.

Position ribbon cable before installation.

Camera installed.

Standard RaPi Camera software

Run Raspberry and add two line to file /boot/config.txt:

start_file=start_x.elf
fixup_file=fixup_x.dat

restart Raspberry.

If you  want turn off led dide on board camera add line to /boot/config.txt:

disbale_camera_led=1

When you login, you can take a picture or record a video.
Take a picture:

# /opt/vc/bin/raspistill -o testimage.jpg

Record 10 seconds video:

 # /opt/vc/bin/raspivid -t 10000 -fps 25 -o testvideo.h264 

links:

http://www.raspberrypi-spy.co.uk/2013/05/the-official-raspberry-pi-camera-module/

http://archpi.dabase.com
http://www.raspberrypi.org/tag/camera-board/

https://www.modmypi.com/raspberry-pi-camera-board

http://elinux.org/Rpi_Camera_Module

Firmata - Raspberry Pi (part 2a, access from python)

Introdution

We have prepared earlier Arduino with an installed library Firmata (post how to prepare Arudino with firmata - link). Now we connect from the Raspberry to the Arduino with Firmata. We have the possibility to connect from most programming languages.

We need

• Raspberry Pi with installed ArchLinux
• Arduino(Mega) with installed Firmata library (Firmata - Arduino)

The ArduinoMega connected to the Raspberry Pi

Installation Python 2.7

refresh of all package list:

# pacman -Syy

install python:

# pacman -Sy python2 python2-pip python2-virtualenv

test installation:

# python2 --version

we should see something like:

Python 2.7.6

if all is ok, create python enviroment:

# mkdir robot   
# cd robot/
# virtualenv2 --no-site-packages python_firmata_test
# cd python_firmata_test/
# source bin/activate

install pySerial:

# pip2 install pyserial

install pyFirmata:

# pip2 install pyfirmata

Now we can write simple application that controls LED13 on Arduino, full code of this app is below (file binkingLed13.py):

from pyfirmata import ArduinoMega, time
board = ArduinoMega('/dev/ttyUSB0')

while True:
   board.digital[13].write(1)
   time.sleep(1)
   board.digital[13].write(0)
   time.sleep(1)

We can run this command:

# python binkingLed13.py

After a few seconds, the LED should start blinking at a frequency of 1 Hz. To exit, press ctrl + c
  

Localization LED13

If you have problems with usb port you can list usb ports:

# ls /dev/ttyUSB*

links:
https://www.python.org/
https://pypi.python.org/pypi/pyserial/2.7 
https://pypi.python.org/pypi/pyFirmata/0.9.5

Firmata - Arduino (part 1)

Introduction

First step is installation Firmata library on Arduino shield. Installed library allows to use Arduino as the A/D and D/A. The control logic will be on Raspberry and communicate will be over USB (Firmata protocol) with Arduino.

We need

• Arduino board (in my example is it ArduinoMega)
• Arduino IDE Software
• PC with USB port ;)

ArduinoMega board

Arduino IDE Software

Download and install Arduino IDE from page http://arduino.cc/en/Main/Software

Connect Arduino to PC and run Arduino IDE:

# sudo ./arduino

If you use linux, you need to use root (sudo) access to have access to the USB port.

select valid Arduino port:

select valid Arduino board:

select Standard Firmata library:

compile and send library to Arduino board:

It's all. Arduino is ready.

We can't test without a second module - Raspberry. How to connect with Rasspbery I will explain in the next post.


links:
http://arduino.cc/en/Main/Software
http://firmata.org/wiki/Main_Page

Wifi static IP configuration

Introdution

If we want to have a cool wireless robot with which we can remote communicate we need a wireless communication. The best and also the easiest solution seems to be a standard network connection over wifi.

We need

• Raspberry Pi with ArchLinux
• wifi dongle
• enabled and configured wifi router

 

Wifi dongle

Wifi dongle detection

Plug the wireless dongle into the USB port of Raspberry. Check if the device has been detected, call:

# lsusb

We should see some WLAN adapter, for example:

depending on the wifi dongle written information can be a bit different. On these screens is very cheap and popular device.

Configure static IP

copy example config file:

# cp /etc/netctl/examples//wireless-wpa-static /etc/netctl/robot-wireless-profile

edit new file (you can run more intuitive editor than the vi ;))

# vi /etc/netctl/robot-wireless-profile

 contents of the file:

Description='Lets make a robot example'
Interface=wlan0
Connection=wireless
Security=wpa
ESSID='ssid_of_your_network' #edit this line
Key='your_wpa_shared_key' #edit this line
IP=static
Address='your_static_ip/24' #edit this line
Gateway='192.168.1.1'
DNS=('dns_server1' 'dns_server2')
# Uncomment this if your ssid is hidden
#Hidden=yes

in most default configured networks just modify four lines (yellow text).

Parameter:

Security=wpa

is valid for both WPA and WPA2.

run wifi connection:

# netctl start robot-wireless-profile

if there are no errors check the connection:

# ifconfig

we should see:

To wifi connection was established at system startup you need to call:

# netctl enable robot-wireless-profile

The final test

• stop ArchLinux:
  

  # shutdown

• unplug the ethernet cable
• reconnect the power
• try to connect to your wifi ip, eg (change the IP 192.168.1.112 to your):

  # ssh root@192.168.1.112
  

links:

https://wiki.archlinux.org/index.php/netctl

Install ArchLinux

We need

• Raspberry Pi
• SD Card, minium 4GB
• Power supply
• LAN connection and Wi-Fi router
• PC with SD card connector (I describe operation on Ubuntu, it's possible use Windows)

Install image ArchLinux

Download image ArchLinux from http://www.raspberrypi.org/downloads/


unpack:

$ unzip ./ArchLinuxARM-2014.01-rpi.img.zip

call command:

$ lsblk

example response:

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sr0     11:0    1  1024M  0 rom 
sde      8:64   0 929.5G  0 disk
├─sde1   8:65   0   100M  0 part
├─sde2   8:66   0  97.6G  0 part
├─sde3   8:67   0     1K  0 part
├─sde4   8:68   0  1023K  0 part
├─sde5   8:69   0   293G  0 part /
├─sde6   8:70   0     8G  0 part [SWAP]
└─sde7   8:71   0 530.9G  0 part

insert SD card, wait few seconds and call again:

$ lsblk

example response:

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sr0     11:0    1  1024M  0 rom 
sda      8:0    1  14.9G  0 disk
└─sda1   8:1    1  14.9G  0 part /media/0C11-B443
sde      8:64   0 929.5G  0 disk
├─sde1   8:65   0   100M  0 part
├─sde2   8:66   0  97.6G  0 part
├─sde3   8:67   0     1K  0 part
├─sde4   8:68   0  1023K  0 part
├─sde5   8:69   0   293G  0 part /
├─sde6   8:70   0     8G  0 part [SWAP]
└─sde7   8:71   0 530.9G  0 part

On the second call, we see an additional drive sda. On my computer it is sda, on the other may be another drive. You need to be sure 100% that actually you call the name of the inserted SD card.

copy linux image to sd card (WARNING: change sda to name in your system. If you enter the wrong parameter, you can delete your data on HDD!):

$ sudo dd if=./ArchLinuxARM-2014.01-rpi.img of=/dev/sda bs=4096

next call:

$ sudo sync

Default ArchLinux image create 2GB partition. You can use the GParted to expand the partition to the entire SD card.

Screen before changes.

Screen after changes.

Insert SD card to Raspberry Pi, insert Wi-Fi dongle, connect LAN cable and supply power. In my description you don't need connect keyboard and monitor to Raspberry.

We have to wait a few minutes and we scan network from your PC (we need to determine Raspberry IP address):

$ sudo nmap -sP 192.168.1.*

You can compare results before and after connection Raspberry. New IP address is probably Raspberry Pi address. In my example is it 192.168.1.102. We can login via ssh:

$ ssh root@192.168.1.102

Default password is root

Change password, call:

# passwd

Upgrade ArchLinux:

# pacman -Syu

Real time clock

RaPi doesn't have a real-time clock. In many cases, time is needed (for example, an HTTPS connection and verification certificates). We can install Network Time Protocol daemon:

# pacman -S ntp

 We can check the current date and time, call:

# date

If the time is in the wrong time zone, we can change it. Below are a few useful commands.

To check the current zone:

# timedatectl status

To list available zones:

# timedatectl list-timezones

To change the time zone to the Warsaw zone:

# timedatectl set-timezone Europe/Warsaw

links:
http://www.raspberrypi.org/downloads/
http://superuser.com/questions/352598/how-to-find-the-dev-name-of-my-usb-device
http://raspberrypi.stackexchange.com/questions/266/how-can-i-keep-system-time
https://wiki.archlinux.org/index.php/time
 

A robot idea

I have an idea to build a robot who connect two popular devices:

- Raspberry Pi

- ArduinoMega

Raspberry Pi is great platform for building advanced  system on a linux platform. We can easy add wifi/internet services, video streaming, audio advanced systems.

ArduinoMega has other adavantages, board has many input/output digitals and analogs. There are a lot of pages describing how to connect various devices.

  

I would like to combine the advantages of these two devices.

Scheme of the robot.

links:
http://www.raspberrypi.org/
http://arduino.cc/en/Main/ArduinoBoardMega