Windows ™ versus Linux on intel Galileo

August 27, 2014 Kenny Millar Electronics, Galileo, Hardware, Software, 0

Here is a really quick and dirty, non scientific comparison of a Galileo GEN1 board running Windows ™ against the same board running linux.
SPI Flash version is 1.0.2.

Login to windows is via telnet.
Login to linux is via ssh.

 Time taken from power-on to login:

Linux  48 Seconds
Windows 68 Seconds

Time taken to power off:

Linux    3.25 Seconds 
Windows  12.54 Seconds

Next I wrote a simple ‘blink’ executable thats sets up Pin 13 for GPIO and then turns it on/off in a tight loop. Source code for both is below. Both are built in ‘release’ mode.

To write the app for Windows on Galileo you need an external PC running Windows 7 or later, and Visual Studio 2013 or later, with the Microsoft IoT dev kit extensions installed.

To write the app for Linux, you need any PC or Terminal capable of attaching via telnet or RS232.

Size of simple ‘blink’ executable

Linux  10080 Bytes
Windows 19456 Bytes

Speed of executing GPIO Writes
The simple app after setting up the GPIO runs in a tight loop just switching the GPIO Pin to 1 and 0 continuously.

The Linux loop:

while(1)
{
    write(fd,"1",1);
    write(fd,"0",1);
}

The windows loop:

while(1){
    digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
    digitalWrite(led, HIGH);  // turn the LED on by making the voltage HIGH
}

These gave the following results:

The Linux version gave a steady 223.9 Hz square wave with a 50% duty cycle. Pulse width is about 2.24 ms.

The Windows version gave a jittery 42.72 Hz wave with a 35% Duty cycle. Pulse width is about 14.97 ms, but there were occasional gaps in the wave form where it paused for 10 ms or so.

And finally, the full source code for each of the test apps.

Linux source code:

#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>

void setGPIOPin(char* pin, char* dir, char* drive, char* val)
{
  char buf[256];
  int fd;

  // Open the GPIO Export file
  fd = open("/sys/class/gpio/export",O_WRONLY);
  if(fd == -1)
    exit(-1);

// Export chosen pin
 write(fd, pin, strlen(pin)); // Export GPIO pin
  close(fd);

  // Open exported pin DIRECTION file
  sprintf(buf,"/sys/class/gpio/gpio%s/direction",pin);
  fd = open(buf,O_WRONLY); // open GPIOxx direction file

  if(fd==-1)
  exit(-1);

  // write out the direction
  write(fd,dir,strlen(dir)); // set GPIOxx direction to out
  close(fd);

  // open the drive file
  sprintf(buf,"/sys/class/gpio/gpio%s/drive",pin);
  fd = open(buf,O_WRONLY); // open GPIO drive strength file
  if(fd==-1)
    exit(-1);

 write(fd,drive,strlen(drive)); // set GPIO drive
  close(fd);

  sprintf(buf,"/sys/class/gpio/gpio%s/value",pin);
  fd = open(buf,O_WRONLY);
  if(fd==-1)
  exit(-1);

  write(fd,val,strlen(val)); // set GPIO value
  close(fd);
}

void setMux(void)
{
  // Switch all the SPI1 pins through to the header pins. And enable level shifter.
  setGPIOPin("55","out","pullup","1"); // mux
  setGPIOPin("39","out","pullup","1"); // Pin 13
  setGPIOPin("4","out","pullup","1"); // Level shifter
}

int main(int argc, char *argv[])
{
  int fd;
  setMux();

  fd = open("/sys/class/gpio/gpio39/value",O_WRONLY);
  if(fd==-1)
  {
    printf("Failed to open GPIO On pin 13\n");
    exit(-1);
  }

  while(1)
  {
    write(fd,"1",1);
    write(fd,"0",1);
  }

  return 0;
}

Windows Source code:

#include "stdafx.h"
#include "arduino.h"

int _tmain(int argc, _TCHAR* argv[])
{
    return RunArduinoSketch();
}

int led = 13;  // This is the pin the LED is attached to.
void setup()
{
    pinMode(led, OUTPUT);      // Configure the pin for OUTPUT so you can turn on the LED.
}

// the loop routine runs over and over again forever:
void loop()
{
    digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
    digitalWrite(led, HIGH);  // turn the LED on by making the voltage HIGH
}

comparison, galileo, linux, windows

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