## Monday, 9 July 2012

### Raspberry Pi and the Kinect

There are several forum posts asking if the Raspberry Pi could be used with the kinect so I decided to give it a try. It is important to note that you will need a powered USB hub, as whilst the kinect does have a PSU this is only used for the motor, the Camera and Audio sub systems still need more power than the Pi can produce.

First you will need to get a couple of libraries, first off libusb is required, I downloaded the latest 1.0.9 tarball and built it using the following commands

tar vfxj libusb-1.0.9.tar.bz2
cd libusb-1.0.9/
./configure
make
sudo make install

This should work fine for both of the debian versions and this will install the developer libraries and headers for libusb. Next I downloaded the OpenKinect source code from git hub unzip this file and change into the source directory.

You may need to install cmake if you have not already done so, this can be done by using sudo apt-get install cmake. Next we need to edit some of the cmake files as for this example I don't want to build the demos which require libraries which will not work properly on the pi.

If you edit the CMakeLists.txt file and search for the following line

OPTION(BUILD_EXAMPLES "Build example programs" ON)

And change the ON to OFF you should now be able to build by typing the following
cmake CMakeLists.txt
make
sudo make install

This will then install the following files
ls /usr/local/include/libfreenect/
libfreenect.h  
libfreenect-registration.h
libfreenect_sync.h

and
ls /usr/local/lib/libfree*
/usr/local/lib/libfreenect.a
/usr/local/lib/libfreenect.so.0.1
/usr/local/lib/libfreenect_sync.a
/usr/local/lib/libfreenect_sync.so.0.1
/usr/local/lib/libfreenect.so
/usr/local/lib/libfreenect.so.0.1.2

The first demo I've tried is a modified version of the tiltdemo.c There are reports of this working fine for some people, however it didn't for me under the latest wheezy build so I investigated more and found that the sync library wasn't working for me. The following program uses the Normal freenect library calls instead.
#include "libfreenect.h"
#include <cstdlib>
#include <ctime>
#include <iostream>

int main(int argc, char *argv[])
{
// seed rng generator
srand(time(0));
// pointer to the freenect context
freenect_context *ctx;
// pointer to the device
freenect_device *dev;

if (freenect_init(&ctx, NULL) < 0)
{
std::cout<<"freenect_init() failed\n";
exit(EXIT_FAILURE);
}
// set the highest log level so we can see what is going on
freenect_set_log_level(ctx, FREENECT_LOG_SPEW);

int nr_devices = freenect_num_devices (ctx);
std::cout<<"Number of devices found: "<<nr_devices<<"\n";
// I only have one kinect so open device 0
if (freenect_open_device(ctx, &dev, 0) < 0)
{
std::cout<<"could not open device error\n";
freenect_shutdown(ctx);
exit(EXIT_FAILURE);
}
// now I'm going to loop and set random value
// these are basically from the tiltdemo.c that comes with
// the freenect lib modified not to use the sync lib
while (1)
{
// Pick a random tilt and a random LED state
freenect_led_options led = (freenect_led_options) (rand() % 6); // explicit cast
int tilt = (rand() % 30)-15;
freenect_raw_tilt_state *state = 0;
double dx, dy, dz;
// Set the LEDs to one of the possible states
freenect_set_led(dev,led);
// Set the tilt angle (in degrees)
freenect_set_tilt_degs(dev,tilt);

// Get the raw accelerometer values and tilt data
state=freenect_get_tilt_state(dev);

std::cout<<"led["<<led<<"] tilt["<<tilt<<"]\r" ;
std::cout.flush();
sleep(1);
}
}


To build this I used the following makefile
CC=g++
CFLAGS=-c -Wall -O3 -I/usr/local/include/libfreenect
LDFLAGS=-L/usr/local/lib -lfreenect
SOURCES=tiltdemo.cpp
OBJECTS=$(SOURCES:%.cpp=%.o) EXECUTABLE=tiltdemo all:$(SOURCES) $(EXECUTABLE)$(EXECUTABLE): $(OBJECTS)$(CC) $(LDFLAGS)$(OBJECTS) -o $@ .cpp.o:$(CC) $(CFLAGS)$< -o $@ clean : rm -f *.o$(EXECUTABLE)


A video of it in action can be seen here