getting sensors in using the MCP3008

Attaching a mcp3008 chip to your pi will give you 8 channels of analogue ins, the pi's pins can be used straight away to register button presses


you can buy a mcp3008 chip here
to get it running, first make sure you have the relevant software and librarys installed, the following libraries are relevant for getting all sorts of inputs in from the pi


in a terminal window

git clone https://github.com/ptone/pyosc.git  

cd pyosc

sudo ./setup.py install

cd

sudo apt-get install python2.7-dev

wget https://github.com/Gadgetoid/py-spidev/archive/master.zip
unzip master.zip

rm master.zip

cd py-spidev-master

sudo python setup.py install

cd
git clone git://git.drogon.net/wiringPi

cd wiringPi

./build

cd

sudo apt-get install python-setuptools python-dev

git clone https://github.com/Gadgetoid/WiringPi2-Python.git

cd WiringPi2-Python/

sudo python setup.py install

cd

git clone git://github.com/guyc/py-gaugette.git

cd py-gaugette

sudo python setup.py install

cd

Next make sure you have your SPI interface enabled on the pi

in terminal

sudo raspi-config

8. Advanced Options

A6. SPI

turn it on

turn on SPI kernal module on default

then reboot the pi

wire-up yer mpc3008

these pictures came from here

this page will show you the different pins on different models of raspberry pi

raspberry pi 1 pins

raspberry pi 2 pins

communicating inputs

the mpc3008 is read by a simple python script, this information is then passed to pd-extend via OSC

the pd patch starts the python patch automaticaly using the shell object
(n.b if auto-starting  the pd patch though updating the rc. file (see starting headlessly) the pd patch needs the full address of the python script

first start up the pd patch, this will open a osc channel, then will open the python script which will start sending the data.

here's some screen shots of how the pd patch works. download the patch here

inside the subpatcher pd sortmes

here is the python script, download it here

#!/usr/bin/python

import spidev

import time

import os

import OSC

import RPi.GPIO as GPIO

# Open SPI bus

spi = spidev.SpiDev()

spi.open(0,0)

# Open osc

send_address = "127.0.0.1" , 9000

c = OSC.OSCClient()

c.connect(send_address)

# Function to read SPI data from MCP3008 chip

# Channel must be an integer 0-7

def ReadChannel(channel):

  adc = spi.xfer2([1,(8+channel)<<4,0])

  data = ((adc[1]&3) << 8) + adc[2]

  return data

# Define sensor channels

l0 = 0

l1 = 1

l2 = 2

l3 = 3

l4 = 4

l5 = 5

l6 = 6

l7 = 7

# Define delay between readings

delay = 0.1

while True:

  # Read the light sensor data

  ll0 = ReadChannel(l0)

  ll1 = ReadChannel(l1)

  ll2 = ReadChannel(l2)

  ll3 = ReadChannel(l3)

  ll4 = ReadChannel(l4)

  ll5 = ReadChannel(l5)

  ll6 = ReadChannel(l6)

  ll7 = ReadChannel(l7)

  msg = OSC.OSCMessage()

  msg.setAddress("print")  

  msg.append(ll0)

  msg.append(ll1)

  msg.append(ll2)

  msg.append(ll3)

  msg.append(ll4)

  msg.append(ll5)

  msg.append(ll6)

  msg.append(ll7)

  

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