Using an Arduino as a slave I/O board

[tonygo2]

Control a slave Arduino from your R-Pi via USB

If you have used the GPIO pins and want to move on to analogue input and PWM (Pulse Width Modulation – pseudo analogue output) you need to add extra hardware to your Pi. I suggest you add an Arduino Uno as a first step. You use it as a slave to your R-Pi and control it from Python via a USB cable. This is very easy to set up, inexpensive and very safe. You will have access to an extra 14 digital I/O pins, 6 with PWM, 6 analogue input pins - 10 bit, (which you can also use for even more digital I/O), and a stand-alone microcontroller which you can later program from your Pi via the Arduino IDE. This arrangement makes it simple control LEDS, 7-segment displays, read switches and voltages and to drive a 16 x 2 liquid crystal display - LCD. The software is called Nanpy and was written by Andrea Stagi, stagi.andrea@gmail.com, who wrote about it in MagPi issue 8, page 12.

Preparing the SD card

You a need a 4 GB class 4 card (slow). Copy the latest version of Raspbian Wheezy onto it and expand the root partition. Reboot the Pi.

Install setuptools
You need python setuptools to install nanpy on your card. This is not in the current distribution. You can download it from the Web.

Start Midori and type in the URL box https://pypi.python.org/pypi/setuptools

Scroll down to the Linux instructions and then on to the downloads. We want the file:
setuptools-0.6c11-py2.7.egg
Click on it and you will be asked to open or download. Click on SAVE. It downloads very quickly.

Close Midori and you should see the egg file in the pi directory.

Open the LX Terminal and type in:

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	sudo sh setuptools-0.6c11-py2.7.egg 

This is a very quick installation.

Install serialpy
Using Midori go to https://pypi.python.org/pypi/pyserial
Download pyserial-2.6.tar.gz
Make a temp folder and move the downloaded file into it.
Using LXTerminal

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cd temp	#Change to the temp directory   
gunzip pyserial-2.6.tar.gz 	#to unzip it
tar –xvf pyserial-2.6.tar 	#to untar it
cd pyserial-2.6	#move into the new folder
sudo python setup.py install	#to install it

Your Pi can now use serial communication

Install the Arduino software
Type ‘startx’ to start the GUI.
Open the LX Terminal.
Type in the the following commands:

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	sudo apt-get update
	sudo apt-get install arduino

Answer ‘Y’ when asked if you want to continue. This installation takes some time…..
You can now program your Arduino from the Arduino IDE.

Install NanpyThe next step is to download the nanpy files:
I find it much easier to do on a Windows PC and then transfer the unzipped folder to the Pi via a memory stick.

On a PC using your browser navigate to https://github.com/nanpy/nanpy and click on the ZIP button. This downloads the zipped directory. Unzip it and copy the nanpy-master directory via a USB stick to your pi directory.

Open the LX Terminal and navigate to the firmware directory in nanpy-master.
Connect your Arduino via a USB cable to the Pi.

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cd nanpy-master
cd firmware
export BOARD=uno  	#(Type ‘make boards’ for a full list)
make
make upload 	#This also takes some time…….

This section needs to be done each time you connect the Arduino to the RPi if you have re-programmed the Arduino. It loads the Arduino part of nanpy into the Arduino .

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cd .. 	#Move back to nanpy-master directory
sudo python setup.py install

This adds the RPi part of nanpy to Python2 and only needs to be done once. You can now use the Arduino as a I/O board for the Pi

Testing

The Arduino really needs to be connected via a powered USB hub so that it does not take too much power from the RPi.

On your Arduino connect an LED in series with a resistor (about 560 Ohms for protection) between pin 10 and ground. The longer lead of the LED, the anode, goes towards pin10 and the shorter, the cathode, towards GND. Pin 10 allows PWM (Pulse Width Modulation).

From LXED start LXTerminal and type:

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 sudo idle

(With sudo you can run the program from the Run menu in Idle)
Click on File, then New window; to open a new window and type in the following program:

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#!/usr/bin/env python
# LED with 560 Ohm resistor on Pin 10 to GND
# Tony Goodhew - 10 May 2013
from nanpy import Arduino
from nanpy import serial_manager
serial_manager.connect('/dev/ttyACM0')    	 # serial connection to Arduino
from time import sleep

LED =10                     	# LED on Arduino Pin 10 (with PWM)
Arduino.pinMode(LED, Arduino.OUTPUT)

print"Starting"
print"5 blinks"
for i in range(0,5):
    Arduino.digitalWrite(LED, Arduino.HIGH)
    sleep(0.5)
    Arduino.digitalWrite(LED, Arduino.LOW)
    sleep(0.5)

print"Changing brightness of LED"
bright = 128                        	# Mid brightness
Arduino.analogWrite(LED, bright)
Arduino.digitalWrite(LED,Arduino.HIGH)       	# Turn on LED

for i in range(0,200):
    bright = bright + 8
    if (bright > 200):	       # LED already full on at this point
        bright = 0	       # Minimum power to LED
    Arduino.analogWrite(LED, bright)	        # Change PWM setting/brightness
    sleep(0.05)

Arduino.digitalWrite(LED,Arduino.LOW)       	# Turn off LED
print"Finished"

Save and run the program from the idle menu.

Problem:
If you pull the USB cable out of the Arduino while the Pi is controlling it you may need to re-boot the Pi before it will re-connect.

Comments, feedback and questions would be appreciated.

Tony Goodhew

[m0rgo]

If you want a quick test of functionality, the Arduino (at least the R3 and Nano versions anyway) has an onboard LED with built-in resistor, connected to pin 13.

Using the Arduino IDE, select the 'Blink' sketch from the example menu (File, Examples, Basic, Blink), upload to the Arduino and enjoy the fairly unremarkable blinking LED - but you will at least know the Arduino and Pi are communicating and the Arduino is functioning.


...then you can get fancy!

[3gws]

Hello Tony thanks you for the detailed post. Have you actually tried this and does it work ?.

I had originally looked at a project in the Magpi 8th Edition Magazine using 433.93 Mhz modules and I gave it a try and abandoned it on the R-Pi. The funny thing is the article you mentioned in your post was the one after it but I did not read it . I have since completed the project using the Arduino UNO and I am just about to use the R-Pi as my Networking Shield to the Cloud. I did not want to have to learn yet another language (Python) but after reading your article I think this is the answer to my Prayers (as the saying goes). 700Mhz Processor, 512MB Ram Ethernet, USB, Serial Port, Flash and the Arduino Uno together what a combination !


I have been using C# Mono on the R-Pi but I am not really sure what direction that is going in, in terms of hardware floating point support as the control seems to be with a Commercial Organisation. What is Pythons performance like, I am not trying to compare it to C# Mono on the R-Pi.

The R-Pi and Arduino are really great together and I am really interested in giving this ago. I have a fresh clean SD Card and I am going to follow your instructions to the 'T'

The Arduino Library I am using would need to be converted to Python. I found a tool/Script called Cpp2Python
https://github.com/hlamer/cpp2python that might be of use. I must learn to crawl first though (learn Python).
I know a little C++, enough to get me by.

Once again thanks for your article.

3gws

[6677]

Hello Tony thanks you for the detailed post. Have you actually tried this and does it work ?.

I had originally looked at a project in the Magpi 8th Edition Magazine using 433.93 Mhz modules and I gave it a try and abandoned it on the R-Pi. The funny thing is the article you mentioned in your post was the one after it but I did not read it . I have since completed the project using the Arduino UNO and I am just about to use the R-Pi as my Networking Shield to the Cloud. I did not want to have to learn yet another language (Python) but after reading your article I think this is the answer to my Prayers (as the saying goes). 700Mhz Processor, 512MB Ram Ethernet, USB, Serial Port, Flash and the Arduino Uno together what a combination !


I have been using C# Mono on the R-Pi but I am not really sure what direction that is going in, in terms of hardware floating point support as the control seems to be with a Commercial Organisation. What is Pythons performance like, I am not trying to compare it to C# Mono on the R-Pi.

The R-Pi and Arduino are really great together and I am really interested in giving this ago. I have a fresh clean SD Card and I am going to follow your instructions to the 'T'

The Arduino Library I am using would need to be converted to Python. I found a tool/Script called Cpp2Python
https://github.com/hlamer/cpp2python that might be of use. I must learn to crawl first though (learn Python).
I know a little C++, enough to get me by.

Once again thanks for your article.

3gws

Dont use the version of mono available via sudo apt-get. Look at this instead: http://www.raspberrypi.org/phpBB3/viewt ... 34&t=37174
More reliable than the official one.

Mono *should* be faster than python but still isnt particularly quick. You want speed, C or C++. Python is probably fast enough for your needs though and by extension mono should be too.

[3gws]

6677, thanks for your reply, I have already installed that version of Mono and I have managed to get some GDI+ stuff running on the R-PI and yes I am quite amazed that it runs on a piece of kit that cost me €35.00.

My preferred language is C# and I suppose what interests me about this project is actually using the power of the R-Pi and the I/O of the Arduino UNO directly from with in the Python script, it has many advantages. I wonder if you can assign interrupt routines to pins on the UNO from within a Python script. I already have some small Apps communicating to a running sketch on the UNO through the Serial port with C#. I can use this method to talk with a Mega 2560 also and still have serial ports available on the Arduino side. 'If it ain't Broke don't fix it'

Regards

3gws

[tonygo2]

Have you actually tried this and does it work ?.

Of course I've tried it and was demonstrating it at the Raspberry Jam in York at the weekend.

Here is the Python program I was using to show both digital and analogue input/output.

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#!/usr/bin/env python
# LED with 560 Ohm resistor on Pin 10 to GND
# Button switch on pin 8 with 10K ohm pull up resistor
# 10K ohm potentiometer between 5v and GND with wiper to A0
# LCD 16x2 on pins 7,6,5,4,3,2
# Tony Goodhew - 2 June 2013

from nanpy import Arduino
from nanpy import serial_manager
serial_manager.connect('/dev/ttyACM0')     # serial connection to Arduino
from time import sleep
from nanpy import Lcd
lcd = Lcd([7,6,5,4,3,2], [16,2])  # Set up LCD - Digital output

button = 8                   # Button switch on pin 8
LED = 10                     # LED on Arduino Pin 10 (with PWM - analog output)
pot = 14                     # Pot on A0 - Analog input

Arduino.pinMode(button, Arduino.INPUT)# Set Button pin for input
Arduino.pinMode(LED, Arduino.OUTPUT)  # Set LED pin for output
print"Starting"
lcd.printString("LCD Demo", 0, 0)     # message on LCD line 1
sleep(2.5)
sw = Arduino.digitalRead(button)      # Get open value of switch

sw1 = Arduino.digitalRead(button)     # digital input
lcd.printString("Press button", 0, 0)
while (sw1 == sw):                     #Wait until switch is pressed
    sw1 = Arduino.digitalRead(button)

lcd.printString("Turn LEFT POT", 0, 0)

print"Turn the pot - Analogue input - 10 bit"
for i in range(0,25):
    val = Arduino.analogRead(pot)     # Analog input
    print val
    lcd.printString(val, 0, 1)
    lcd.printString("     ")
    sleep(0.3)

lcd.printString("      ", 0, 1)      # message on LCD line 2
lcd.printString("Flash LED x5   ", 0,0)

print"Flash the LED 5 times - Digital output"
for i in range(0,5):
    lcd.printString(i+1, 0 , 1)      # Count flashes on LCD
    Arduino.digitalWrite(LED, Arduino.HIGH)  # LED on
    sleep(0.5)
    Arduino.digitalWrite(LED, Arduino.LOW)   # LED off
    sleep(0.5)
lcd.printString("        ", 0 ,1)

lcd.printString("LED brightness", 0 ,0)
print"Changing brightness of LED"
bright = 80                          # Set to mid brightness
Arduino.analogWrite(LED, bright)     # Turn on LED at power = brightness

for i in range(0,110):
    bright = bright + 10
    if (bright > 180):               # LED at full brightness
        bright = 0
    Arduino.analogWrite(LED, bright)
    sleep(0.2)

Arduino.digitalWrite(LED,Arduino.LOW)       # Turn off LED

print"Turn the pot - Analogue input - 10 bit"
print"Control brightness of LED"
lcd.printString("Turn LEFT POT   ", 0, 0)
lcd.printString("         ", 0, 1)

for i in range(0,50):
    val = Arduino.analogRead(pot)
    bright = val/5                 # Scale down analog value
    print val, bright
    lcd.printString(val, 0,1)
    Arduino.analogWrite(LED, bright)  #Set LED brightness
    sleep(0.1)
    lcd.printString("     ", 0, 1)

Arduino.digitalWrite(LED, Arduino.LOW)     # Turn off LED
print"Finished"
lcd.printString("Finished        ", 0,0)
lcd.printString("      ",0,1)
sleep(2.5)
lcd.printString("           ", 0,0)        # Clear LCD screen

Tony Goodhew

[joan]

Arduino's have analogue inputs. The rest you can do on a Pi.

http://www.raspberrypi.org/phpBB3/viewt ... 9&p=368070

[tonygo2]

Arduino's have analogue inputs. The rest you can do on a Pi.

http://www.raspberrypi.org/phpBB3/viewt ... 9&p=368070

I agree. Your post is very interesting and very powerful but needs a great deal of previous knowledge to get it going.

I'm interested in getting people new to Pi, and nervous, to take their first steps in control. They will still be struggling with python and unsure about connecting other bits to their Pi. Many will only have 'pocket money' amounts to spend on their new hobby. Your system is fantastic but would require an enormous learning curve and loads of time for a new Pi user to make use of it.

Tony Goodhew

[ficeto]

I wrote a simple I2C communication that lets you read/write to arduinos really easily. Full source and all is at http://www.raspberrypi.org/phpBB3/viewt ... 44&t=46969. Not to promote my thread, but I was searching for days what's the best way to use the arduino with the Pi and the method above does not need anything but 3 wires to connect them both. Also lets you control more than one arduino connected to the I2C bus which lets you expand the ports you can access vastly. From the example I'm sure you can work out a python version, but I'm just really new at python and prefer compiling a binary that I can later call from a web interface, so on.

[simplesi]

@tony
Great idea -I've previously used PyFirmata to do the same sort of thing on PCs - I'll have to check out this NanPy and see if its goign to be better maintained than Firmata.

Compared to joan's stuff - your is simpler but not simple enough for my liking

if looking to attract beginners then I'd recommend trying to make up an install script to load all the components needed to get all of this to work

Basically, instructions should be - click on this - sudo that - and then Bert will become your aunties brother

Example of my installer stuff for Scratch GPIO https://github.com/cymplecy/scratch_gpi ... /installer

Simpler straightforward Samba install script http://cymplecy.wordpress.com/2012/08/0 ... mba-setup/

regards
Simon

[3gws]

Thanks Tony for your response, I am currently spinning up a new 8GB SD card to install everything on it as per your post.

Regards

3gws

[tonygo2]

if looking to attract beginners then I'd recommend trying to make up an install script to load all the components needed to get all of this to work

Basically, instructions should be - click on this - sudo that - and then Bert will become your aunties brother

Example of my installer stuff for Scratch GPIO https://github.com/cymplecy/scratch_gpi ... /installer

Simpler straightforward Samba install script http://cymplecy.wordpress.com/2012/08/0 ... mba-setup/

regards
Simon

Great idea but I am not yet up to doing it. I'd love somebody else to take on the task and post the result. Best of luck if you want to take it on. I'm not a great fan of Github for beginners.

Tony Goodhew

[vinodmadhu6]

I have tried using the avr board (atmega 16) processor but when i try to give the command make upload
the following error comes up

Uploading to board...
error: SERIALDEV could not be determined automatically.
make: *** [upload] Error 1

"
what do i do i just want to make a simple program to blink an led from the atmega 16 board ?
atmega 16 data sheet http://www.atmel.com/Images/doc2466.pdf

i have followed the complete procedure given in magpi 15 th edition http://magpi.finalart.hu/The-MagPi-issue-15-en.pdf
Topic :Using Nanpy to connect your Raspberry Pi to an Arduino

[tonygo2]

I've only used this with a full Arduino board - Uno R3, not just a chip. Nanpy expects you to specify the board type. Does the chip have a bootloader?

Tony Goodhew

[vinodmadhu6]

Yes the chip has a boot loader. I was able to program it using windows xp with hid flash boot loader.

[tonygo2]

Great - is it working OK now?

Tony

[vinodmadhu6]

Its working with my pc. NO luck from my RPI. i am not able to understand what board should i select in my Rpi audrino (software). from tools boards..??

[tonygo2]

Not tried it from a PC - only from a Pi with an official board. You are not using an official board - so no name. I use an Uno R3. if you type ' make boards' while in the nanpy-master directory it should list all the boards supported.

Unfortunately the guy who wrote the Nanpy software - stagi.andrea@gmail.com does not seem to answer emails. Have you looked at MagPi issue 8 , page 12 for his original piece?

Could you write up how got it working from a PC. I'm sure there are many who would be interested.

Tony

[vinodmadhu6]

what role does it have to play with the board?
cant we program the Micro controller with the PI ?
its just flashing right or does every board have different library s ?
i got the board from my college workshop. and i think its a unbranded one made locally ...

[tonygo2]

If you want to program the Arduino from the Pi you use the Arduino IDE which you have already put on your card. Go to the Arduino website for full information: arduino.cc

Tony

[tonygo2]

Your problem with an unofficial Arduino board may because it uses a different serial chip for the USB. I've just got a Sparkfun RedBoard and it uses different drivers from the genuine Uno R3. Works perfectly from my PC but the writers of Nanpy have only teasted it with a 'real' Arduino.

Tony

[IanH]

I've got some code which lets you use either an Uno attached via USB, or a Mini or raw AtMega328 attached to the GPIO serial port, as a general slave I/O device.

To get it via git, go to a suitable working directory and do:

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sudo apt-get install git-core
git clone https://github.com/IanHarvey/arduino-daq.git

There's some pre-built firmware and a Python script to load it - you don't need the Arduino IDE installed. For a Uno on USB, do:

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cd arduino-daq/
python ardprog.py --usb dlpio8_emu.hex

The firmware you've just loaded will do analogue input and one-wire temperature reading (for a DS18B20 chip). There's a test program, daq_dlpio8.py which issues serial commands to the Arduino to read analogue inputs and do one-wire (DS18B20) temperature input. To run it on a Uno, you'll need to change the serial port to /dev/ttyACM0, i.e. edit the program so it looks like this:

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if __name__ == '__main__':
    daq = DLPIO8("/dev/ttyACM0")

   # ...

If you want to customise the firmware, the sketch is in firmware/dlpio8_emu.ino, which you can build either with the Arduino IDE or from the command line with the supplied Makefile - you'll need to edit the first line to tell it where the Arduino AVR compiler is.

I intended this as a starting point for people to make their own custom I/O controllers with, so I'm happy to answer questions on hacking it.

Ian

[vinodmadhu6]

I ll try it today .

[richiepp]

I've wanted to do this since I first got my Pi. Thanks for the tutorial.

I made two scripts, a simple on and simple off. The work as intended but the on script takes about 2 seconds to execute, the off script is instantaneous, or close enough.

What's going on? How can I make the on script run quicker?

from nanpy import Arduino
from nanpy import serial_manager
serial_manager.connect('/dev/ttyACM0') # serial connection to Arduino
# serial_manager.connect('/dev/serial/by-path/platform-bcm2708_usb-usb-0:1.2:1.0-port0') # serial connection to$

LED = 10 # LED on Arduino Pin 10 (with PWM - analog output

Arduino.pinMode(LED, Arduino.OUTPUT) # Set LED pin for output

Arduino.digitalWrite(LED, Arduino.HIGH) # Turn off LED

print"On"

[Sertok]

Hey Tony!

Thanks for your detailed post. I've already read it in MagPi#15 and tried it out yesterday.
Sadly it won't work (different releases, etc.). Since i'm really fresh to the raspi and arduino, i'm already at my limit.

Here's what i did:
- I downloaded and installed setuptools-2.1 => no errors
- I downloaded and installed pyserial-2.7 => no errors
- I installed the Arduino GUI => no errors
- I downloaded and unpacked Nanpy
- I connected my Arduino Uno R3 to my Raspberry Pi Model B and it powered up (both are connected via USB-hub)

I'm able to use "export BOARD=uno", but wether "make" nor "make boards" works.
Is there a way to test the serial connection between the Arduino board and the raspi? My guess is, that this is the real problem.

I'm really new to this, so please excuse "dumb questions" with obvious answers
I've already tried for 4 hours without any visible progress