#include <msp430x14x.h>

void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
P6DIR |= 0x08; // P6.3 Set P6.3 to output
CCTL0 = CCIE; // CCR0 interrupt enabled
CCR0 = 60000;
TACTL = TASSEL_2 + MC_2; // SMCLK, contmode
_BIS_SR(GIE); // Enable interrupt
}

// Timer A0 interrupt service routine
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A (void)
{
P6OUT ^= 0×08; // Toggle P6.3
CCR0 += 60000; // Add Offset to CCR0
}

If you run this code you and observe the signal, you get a screen shot something similar to

Some Experiments

Here are some experiments you can do.

1. Try changing

CCR0 += 60000;

to

CCR0 += 30000;

and you will observe that time period becomes half. Changing it to CCR0 += 6000; will reduce it to 1/10th.

2. If you want a slower timer, you may change the

TACTL = TASSEL_2 + MC_2;

to

TACTL = TASSEL_1 + MC_2;

Which will change the clock from SMCLK ( derived from 4 MHz) to ACLK ( derived from 32.768 KHz).
3. If you change

TACTL = TASSEL_2 + MC_2 ;

to

TACTL = TASSEL_2 + MC_2 + ID_1;

it doubles the time period ( by by halving the clock period used for timer interrupt). Bit 7-6 defines it.

IDx Bits

00 divide by 1
01 divide by 2
10 divide by 4
11 divide by 8

void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
P6DIR |= 0x08; // P6.3 Set P6.3 to output
CCTL0 = CCIE; // CCR0 interrupt enabled
CCR0 = 60000;
TACTL = TASSEL_2 + MC_2; // SMCLK, contmode
_BIS_SR(GIE); // Enable interrupt
}

Let is now try to understand the code one by one..

CCTL0 Register

If you plan to use a Timer, the first register that you need to set is CCTL0. It is a 16 bit register and settings of this register effects how we use the register. For our purpose we just tell it to enable the interrupt using

CCTL0 = CCIE;

Notice that we have not yet enabled the timer.

CCR0

This register will define the amount of time after which the timer event will occur. We have set it to

CCR0 = 60000;

TACTL

Bit 9-8 selects the source of the clock

The Possible values are

00 TACLK
01 ACLK
10 SMCLK
11 INCLK

We have basically selected the SMCLK which is a 4 MHz clock in our case.

The bits 5-4 selects how the counting. Possible values are

00 Stop mode: the timer is halted
01 Up mode: the timer counts up to TACCR0
10 Continuous mode: the timer counts up to 0FFFFh
11 Up/down mode: the timer counts up to TACCR0 then down to 0000h

We have selected 10 which makes the counter count upto 0FFFFh

Enable General Interrupt

Finally we have to enable the general interrupt using.

_BIS_SR(GIE);

This statements sets the GIE bit in the Status register which enables the interrupt. Notice that we have not yet defined the interrupt vector. We will do it in the next page. The code as of now will compile but will not produce any observable result.

Preparing your hardware

Before we start our experiment, let us make sure that our hardware is in place. We do this by writing the following code and checking that we are getting high ( or low ) at an IO port of the board we are testing. In out case it is P6.3, but you can use any other port.

Use the following code and make sure that the P6.3 ( or your chosen port) turns high and low before you start experimenting.

#include "msp430x14x.h"

void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
P6DIR |= 0x08; // P6.3 Set P6.3 to output
P6OUT &= ~0x08; // P6.4 is low
//P6OUT |= 0x08; // Use this if you want to check for high output.
}

In the next page we will write the actual code that will run timer.

There is one solution. Use a tool from accessify.

All you have to do is copy the content of the html that you wish to display in the tool’s text area and click convert to Escape characters. It renders the escaped character into that you can use.

Error initializing COM property pages

and says some “wrong pointer” etc.

Here is a quick solution for it. Take a look at the screen shot

Basically, you need to run the Orcad as an Administrator. You need to do it only the first time.

Go

The Ampere Hour is more intuitive term for expressing the battery life. If a battery is specified at 20 Ampere hour then the implication is simple – A 20 Ampere hour battery life will last for 20 hours if it draws 1 Ampere of current. It will last for 10 hours if it draws 2 Ampere of current. Simple ?

The problem with the Ampere hour specification is that it does not specify the Voltage at the battery. Let us say you have two batteries. Both the batteries A and B has a Ampere Hour rating of 10 Ampere Hour. However, Battery A is at 3.6 Volts while the Battery B is at 7.2 Volts. Now if you draw 1 Ampere of current from both the batteries, both will last 10 hours. But the Battery B is delivering 1 Ampere at 7.2 Volts while the battery A is delivering it at only 3.6 Volts. I strictly technical terms we say that battery B has double the capacity of the battery A.

This is where the Watt hours come in play. If a battery is rated 20 Watt hours, it will mean that it will last for 20 hours if 1 Watt power is drawn from it. Now watt is defined at the product of the Volt ( at the battery) and Ampere ( drawn from the battery).

In the previous example, the 20 Ampere Hour 7.2 Volt battery would be rated as 1440 Watt Hour while the 20 Ampere Hour 3.6 Volt battery would be rated at 720 Watt Hour.

You can use the battery life calculator to calculate the life of a battery. This calculator just calculates the battery life if you know the Ampere Hour rating and the current drawn from the battery.

This formula is valid for a set of n discrete values. If you have a continuous variable, you can use Calculus to derive the formula for various common waveforms, for example the sinusoidal waveform.

For example if a is the amplitude of a sinusoidal waveform the vrms is given by

You can use the following calculator to calculate the rms value , if you know the peak to peak value

rms to peak to peak calculator

Probably you cam here searching for the formula for the Root Mean Square or, rms for the short. Before we give out the formula and the explanation, let us find the need of a root mean square.

A company Xing Hua, makes nuts and bolts and supplies it to various companies in US and Europe. The company makes a strict record of all the quality procedure that it adapts.

The nuts and bolts had their dimensions measured with automatic tools after they are finished and recorded in a spread sheet. That is a great !!! Said the CEO when he visited the shop and looked into the quality procedure adopted by them. The QA engineer then calculated the mean of the internal diameter of the nuts and found that the average of the dimension of is very close to the required dimension. The required dimension was 2.050 mm while their average dimension was 2.051 mm. Pretty close.

A few months later the order that came from Japan for an automobile company was rejected. The company went bankrupt.

Explanation

Had the QA engineer measured the rms average in place or regular average, they could have caught the fault much earlier saving the company from bankruptcy.

You may have now understood the story now. Let us say we want to hit an average dia of 2.50 mm. If one piece has dia of 1.5 mm and second one has a dia of 3.5 mm, the average is still 2.50 mm, but both are useless.

So we define root mean square.

We take the difference. The differences are as follows

For 1.0 mm the difference is +1.0 mm
For 1.5 mm the difference in -1.0 mm

The average is 0
But the root mean square is sqrt ( (1)^2 + (-1)^2) /2) = 1.0

This is 1.0 mm – non trivial value.

So coming back to the rms formula. Here is the formula for the RMS

The rms value of a set of n values for (x1, x2, …..xn) is given by

Other Resources

- If you are, however looking at the rms value corresponding to a waveform, you may like to check vrms to vpeak to peek calculator

1. It takes longer to upload to facebook because of the size.
2. It is impractical to send large size image using email.
3. Viewing large size creates issues when viewing it in some photo viewer.

When you transfer the photos from your camera to your computer, it gets stored in a directory. We wish to write a simple program that will create a new directory and will put all the resized images in the new directory.

Here is goes.

using System;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;

}


If you are uninitiated, you may like to take CSharp Tutorial.

using System;
using System.IO;

}
}


Pay special attention to

Directory.GetFiles(WorkingDirectory,”*.jpg”);

It will list out all the files in the directory with the extension jpg. If you wish to list all files, irrespective of the extension, you may use

Directory.GetFiles(WorkingDirectory);

It will list all files with in the directory WITH path. Here is a typical output

--- List of the Files: ---
C:\Users\abhinsv\Desktop\Imageresize_src\imageresize_horiz.jpg
C:\Users\abhinsv\Desktop\Imageresize_src\imageresize_vert.jpg

If you want to list only the names of the file, you can use

Console.WriteLine(Path.GetFileName(name));

in place of

Console.WriteLine(name);

This will, for example give the following output

--- List of the Files: ---
imageresize_horiz.jpg
imageresize_vert.jpg

If you are uninitiated, you may like to take CSharp Tutorial.

System.IO.Directory.CreateDirectory("C:\directory\subdirectory\newdirectory);

using System;

namespace Tutorial
{
class CreateDirectory
{
static void Main(string[] args)
{
//set a working directory
string WorkingDirectory = @”C:\Users\abhinsv\Desktop\Imageresize_src”;
System.IO.Directory.CreateDirectory(WorkingDirectory + @”\images”);
}

}
}

If you are uninitiated in C Sharp, you may like to check CSharp Tutorial for beginners.

Here is the complete code to do this.