Hong Kong trip postponed.

Aside

I was supposed to travel to Hong Kong on Saturday 11th October to attend HKTDC, but I had to pull out due to a foot injury. Now it looks as though that might have been a provident decision, given the current unrest in the area.  Continue reading

Sep 18

Solder paste under the microscope.

In electronics we regularly use solder paste in the assembly of printed circuit boards (PCBs).
This paste comes in a variety of packages, styles, types and so on. Today I look at one small tub of solder paster under the microscope. Quite literally.  Continue reading

Sep 05

Moto 360 Smartwatch on sale today.

Motorolla’s new “moto 360” goes on sale today at 11:00am Central Time (USA)
More details are available here.

Screen Shot 2014-09-05 at 11.37.02

See the launch video here.

Aug 27

Windows ™ versus Linux on intel Galileo

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.

Screen Shot 2014-08-27 at 15.00.42

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.

Screen Shot 2014-08-27 at 14.36.39

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
}

Aug 15

Galileo GPIO Timing & why it doesn’t work for some.

The Intel Galileo is has Arduino UNO compatibility, yet often I see queries from someone asking why their favourite Arduino Shield won’t work, or why an interface they have made which works on other Arduino boards, doesn’t work with Galileo. Often they say Galileo is no use, or Galileo doesn’t do what it claims, or Galileo is slow. So why do some Sketches and Shields not work as expected, when using GPIO on Galileo? Read on for the answers…

Continue reading

Jul 02

Dallas 1-Wire iButton teardown.

Recently I’ve been investigating 1-wire iButtons and interfacing them to different systems. I thought it might be interesting to see what’s inside an iButton. So here is my Dallas DS1990A iButton teardown.

Continue reading

Jun 17

iPhone self destructs with bulging battery.

My iPhone 4 has dangerously self destructed, with an unexplained bulging of the battery which broke off the rear cover and cracked the front display.  Continue reading

Jun 16

Reading 1-Wire iButtons using Cypress PSoC 3 and 5/5LP

Previously I posted about using a standard UART to read and write to 1-Wire devices. In this post I look at how to read and write to these devices using Cypress PSoC devices. Continue reading

Jun 13

Reading 1-Wire iButtons using a UART

This post takes a look at a simple 1-Wire protocol reader/writer using a standard UART for detecting and communicating with 1-Wire devices. Written in C for Linux, and running on Intel Galileo. It could easily be ported to most other platforms.

Continue reading