Palak Patel's Blog: 2015

Tuesday, November 3, 2015

SAMD21 Features

SAMD21J18A microcontroller
One mechanical reset button
One mechanical user pushbutton (wake-up, bootloader entry or general purpose)
One yellow user LED
32.768kHz crystal
USB interface, device and reduced host mode
8 Mbit Serial Flash
3 Xplained Pro extension headers
Embedded Debugger
- Auto-ID for board identification in Atmel Studio 6.1
- One yellow status LED
- One green board power LED
- Symbolic debug of complex data types including scope information
- Programming and debugging
- Data Gateway Interface: SPI, I²C, 4 GPIOs
- Virtual COM port (CDC)
USB powered
Supported with application examples in Atmel Software Framework

Samd21 Firmware Upgrade(Edbg)





Operation mode Power LED Status LED

Normal operation Power LED is lit when power is applied to the board. Activity indicator, LED flashes every time something happens on the EDBG.
Bootloader mode (idle) The power LED and the status LED blinks simultaneously.
Bootloader mode (firmware upgrade) The power LED and the status LED blinks in an alternating pattern.

Operation mode	Power LED	Status LED
Normal operation	Power LED is lit when power is applied to the board.	Activity indicator, LED flashes every time something happens on the EDBG.
Bootloader mode (idle)	The power LED and the status LED blinks simultaneously.
Bootloader mode (firmware upgrade)	The power LED and the status LED blinks in an alternating pattern.

1->   C:\Users\xxxxx\Documents>atfw -h


Usage: atfw [options] [arguments]

Options:
  -a, --archive .zip
                                 Archive containing firmware upgrade image.

  -h, --help                     Display help information.

  -l, --list                     List connected tools.

  -i, --id                       Print boot loader id (edbg only).

  -t, --tool                Tool name: edbg, medbg, avrone, jtagicemkii, jtagice3
                                 stk600, qt600, avrispmkii or avrdragon.

  -s, --serialnumber        The programmer/debugger serial number.

  -q, --quiet                    Do not display activity indicator.

  -V, --version                  Display version number.

  -r, --read                     Read firmware version on tool.

  -n --nographics                No progress bar, but result alone will be displayed

Example:
  atfw -a myImage.zip -t jtagice3 -s 123456789ABC


2-> C:\Users\xxxxx\Documents>atfw -t edbg -a "C:\Program Files (x86)\Atmel\Atmel Studio 6.2\tools\EDBG\edbg_fw.zip"
Found edbg:ATML2130021800001691
Waiting for bootloader usb enumeration: [==========]
Upgrading MCU: [==========]
Successful upgrade

#include<stdio.h>
typedef struct node
{
int data;
struct node *next;
struct node *prev;
}NODE;

NODE *start=NULL,*top,*temp;

void *Create_Node(int value);
void Insert_At_Last();
void Display_Start_To_End();
void Display_End_To_Start();
void Insert_At_Position();
void Delete_At_Last();
void Delete_At_Position();
void Search();
void Update_Value();
void Node_Count();

void main()
{
int choice;
while(1)
{
printf("\n ENTER CHOISE \n 1.INSERT AT LAST \n 2.Delete_At_Last \n 3.Insert_At_Position \n 4.Display_Start_To_End \n 5.Display_End_To_Start \n 6.Delete_At_Position \n 7.Search \n 8.Update_Value \n 9.Node Count \n 10.Exit \n");
printf("\nEnter Your Choice:");
scanf("%d",&choice);
switch(choice)
{
case 1:
Insert_At_Last();
break;

case 2:
Delete_At_Last();
break;

case 3:
Insert_At_Position();
break;

case 4:
Delete_At_Position();
break;

case 5:
Display_Start_To_End();
break;

case 6:
Display_End_To_Start();
break;

case 7:
Search();
break;

case 8:
Update_Value();
break;

case 9:
Node_Count();
break;

case 10:
exit(0);

default:
printf("\nWrong Choice\n");
}
}
}

void *Create_Node(int value)
{
NODE *new_node;
new_node=(NODE *)malloc(sizeof(NODE));
new_node->data=value;
new_node->next=NULL;
new_node->prev=NULL;
return new_node;
}

void Insert_At_Last()
{
int ch;
NODE *new_node;
printf("Enter The Data:-> ");
scanf("%d",&ch);
new_node=Create_Node(ch);
if(start==NULL)
{
start=new_node;
top=new_node;
}
else
{
top->next=new_node;
new_node->prev=top;
top=new_node;
}
}

void Display_Start_To_End()
{
NODE *temp;
printf("Displaying List From Start to End:->\n");
temp=start;
while(temp!=NULL)
{
printf("%d \n",temp->data);
temp=temp->next;
}
}

void Display_End_To_Start()
{
NODE *temp;
printf("Displaying List From End to Start:->\n");
temp=top;
while(temp!=NULL)
{
printf("%d \n",temp->data);
temp=temp->prev;
}
}

void Insert_At_Position()
{
NODE *new_node;
int ch,pos,cnt=1;
printf("\nEnter the Data:->");
scanf("%d",&ch);
new_node=Create_Node(ch);
printf("\nEnter the position:->");
scanf("%d",&pos);
temp=start;
if(pos==1)
{
new_node->next=start;
start->prev=new_node;
start=new_node;
}
else
{
temp=start;
while(cnt<(pos-1))
{
temp=temp->next;
}
new_node->next=temp->next;
temp->next->prev=new_node;
new_node->prev=temp;
temp->next=new_node;
}
}

void Delete_At_Last()
{
top=top->prev;
top->next=NULL;
}

void Delete_At_Position()
{
int pos,cnt=1;
NODE *temp;
printf("\nEnter the Position:->");
scanf("%d",&pos);
temp=start;
while(pos<=(cnt-1))
{
temp=temp->next;
}
temp->next=temp->next->next;
temp->next->prev=temp;
}

void Search()
{
NODE *temp;
int ch,cnt=1;
printf("\nEnter the data to search:->");
scanf("%d",&ch);
temp=start;
while(temp->next!=NULL)
{
if(temp->data==ch)
{
printf("\nData is at position:->%d \n",cnt);
}
temp=temp->next;
cnt++;
}
}

void Update_Value()
{
NODE *ptr;
int Old_val, New_val, flag = 0;
printf("\n...Updating Node Value...\n");
if (start == NULL)
{
printf("\nNo nodes in the list to update\n");
}
else
{
printf("\nEnter the value to be updated:->");
scanf("%d", &Old_val);
printf("\nEnter the newvalue:->");
scanf("%d", &New_val);
for (ptr = start;ptr != NULL;ptr = ptr->next)
{
if (ptr->data == Old_val)
{
ptr->data = New_val;
flag = 1;
break;
}
}
if (flag == 1)
{
printf("\nUpdated Successfully");
}
else
{
printf("\nValue not found in List");
}
}
}

void Node_Count()
{
int cnt;
temp=start;
while(temp!=NULL)
{
temp=temp->next;
cnt++;
}
printf("\nNO.of Nodes In the list is =%d",cnt);
}

Singly Linked List

#include<stdio.h>

typedef struct node
{
int data;
struct node *next;
}NODE;

NODE *new_node,*temp,*ptr;
NODE *start=NULL,*last=NULL;

void Insert_At_last();
void Insert_At_Position();
NODE *Create_Node(int valu);
void Delete_At_Position();
void Search();
void Display();
void Reverse();
void Update_Value();
void Node_Count();

void main()
{
int choice;
while(1)
{
printf("ENTER CHOISE \n 1.INSERT AT LAST \n 2.INSERT AT POSITION \n 3.DISPLAY \n 4.DELETE AT POSITION \n 5.SEARCH \n 6.REVERSE \n 7.UPDATE VALUE \n 8.NODE COUNT \n 9.EXIT ");
printf("\nEnter Your Choice:");
scanf("%d",&choice);
switch(choice)
{
case 1:
Insert_At_Last();
break;

case 2:
Insert_At_Position();
break;

case 3:
Display();
break;

case 4:
Delete_At_Position();
break;

case 5:
Search();
break;

case 6:
Reverse();
break;

case 7:
Update_Value();
break;

case 8:
Node_Count();
break;

case 9:
exit(0);

default:
printf("\nWrong Choice\n");
}
}
}

NODE *Create_Node(int valu)
{
new_node=(NODE *)malloc(sizeof(NODE));
new_node->data=valu;
new_node->next=NULL;
return new_node;
}

void Insert_At_Last()
{
int val;
printf("\nEnter the data:");
scanf("%d",&val);
new_node=Create_Node(val);
if(start==last && last==NULL)
{
start=last=new_node;
}
else
{
last->next=new_node;
last=new_node;
}
}

void Delete_At_Position()
{
int cnt=0,pos,i;
printf("Enter the Position:->");
scanf("%d",&pos);
if(pos==1)
{
if(start==NULL)
{
printf("\n LIST IS EMPTY \n");
}
else
{
start=start->next;
}
}
else
{
temp=start;
while(pos>2)
{
temp=temp->next;
pos--;
}
temp->next=temp->next->next;
}
}

void Insert_At_Position()
{
int cnt=0,pos,val,i;
printf("Enter the value:->");
scanf("%d",&val);
new_node=Create_Node(val);
printf("Enter the Position:->");
scanf("%d",&pos);
if(pos==1)
{
temp=start;
start=new_node;
start->next=temp;
}
else
{
temp=start;
while(pos>2)
{
temp=temp->next;
pos--;
}
new_node->next=temp->next;
temp->next=new_node;
}
}

void Search()
{
int ch,cnt=1,a=0;
temp=start;
printf("Enter the data:->");
scanf("%d",&ch);
while (temp != NULL)
{
if (temp->data == ch)
{
printf("Data at position:->%d\n",cnt);
a++;
}
temp = temp->next;
cnt++;
}
if(a==0)
{
printf("Data not found\n\n");
}
else
return;
}

void Display()
{
NODE *temp;
temp=start;
while(temp!=NULL)
{
printf("\n%d",temp->data);
temp=temp->next;
}
}

void Reverse()
{
int cnt=0,i=0,pos;
temp=start;
while(temp!=NULL)
{
temp=temp->next;
cnt++;
}
for(i=cnt;i>0;i--)
{
pos=0;
temp=start;
while(pos!=i-1)
{
temp=temp->next;
pos++;
}
printf("%d \n",temp->data);
}
//return;
}

void Update_Value()
{
int Old_val, New_val, flag = 0;
printf("\n...Updating Node Value...\n");
if (start == NULL)
{
printf("\nNo nodes in the list to update\n");
}
else
{
printf("\nEnter the value to be updated:->");
scanf("%d", &Old_val);
printf("\nEnter the newvalue:->");
scanf("%d", &New_val);
for (ptr = start;ptr != NULL;ptr = ptr->next)
{
if (ptr->data == Old_val)
{
ptr->data = New_val;
flag = 1;
break;
}
}
if (flag == 1)
{
printf("\nUpdated Successfully");
}
else
{
printf("\nValue not found in List");
}
}
}

void Node_Count()
{
int cnt=0;
temp=start;
while(temp!=NULL)
{
temp=temp->next;
cnt++;
}
printf("\nNo.Of Nodes in the linked list:->%d\n\n",cnt);
}

Stack Using Linked List

#include<stdio.h>

typedef struct node
{
int data;
struct node *next;
struct node *prev;
}NODE;

NODE *start=NULL,*ptr=NULL,*top=NULL;

NODE *Create_node(int val);
void PUSH();
void POP();
void DISPLAY();

void main()
{
int choice;
while(1)
{
printf("Enter Your Choice\n 1.PUSH \n 2.POP \n 3.DIsplay \nEnter Your Choice:");
scanf("%d",&choice);
switch(choice)
{
case 1:
PUSH();
break;

case 2:
POP();
break;

case 3:
DISPLAY();
break;

default:
printf("\nWrong choice\n");
}
}
}

NODE *Create_node(int val)
{
NODE *new_node;
new_node=(NODE *)malloc(sizeof(NODE));
new_node->data=val;
new_node->next=NULL;
new_node->prev=NULL;
return new_node;
}

void PUSH()
{
NODE *new_node;
int val;
printf("Enter the Value:");
scanf("%D",&val);
new_node=Create_node(val);
if(start==NULL)
{
start=new_node;
top=new_node;
}
else
{
new_node->prev=top;
top->next=new_node;
top=new_node;
}
}

void POP()
{
struct Node *temp, *var=top;
if(start==NULL)
{
printf("\nStack Empty");
}
else
{
top = top->prev;
free(top);
top->next=NULL;
}

}

void DISPLAY()
{
NODE *ptr;
ptr=start;
printf("DATA\n");
if(start==NULL)
{
printf("Stack is empty");
}
else
{
while(ptr!=NULL)
{
printf("%d\n",ptr->data);
ptr=ptr->next;
}
}
}

Stack Using Array

#include<stdio.h>
#define SIZE 5

int stack[SIZE];
int top;

void PUSH();
void POP();
void DISPLAY();
void STACK_COUNT();
void EXIT();

void main()
{
int CHOICE;
while(1)
{
printf("MAIN MENU \n\n 1.PUSH \n 2.POP \n 3.DISPLAY \n 4.STACK COUNT \n5.EXIT \n\nENTER YOUR CHOICE:");
scanf("%d",&CHOICE);
switch(CHOICE)
{
case 1:
PUSH();
break;

case 2:
POP();
break;

case 3:
DISPLAY();
break;

case 4:
STACK_COUNT();
break;

case 5:
EXIT();
break;

default:
printf("\nWRONG CHOISE");
}
}
}

void PUSH()
{
if(top>=SIZE)
{
printf("STACK IS FULL\n\n");
return;
}
else
{
if(top<=0)
top=0;
printf("\nENTER THE ELEMENT:");
scanf("%d",&stack[top++]);
}
}

void POP()
{
if(top<=0)
printf("\nSTACK IS EMPTY\n\n");
else
{
printf("\nPOPED ELEMENT:%d\n\n",stack[--top]);
}
}

void DISPLAY()
{
int i;
if(top<=0)
printf("\nSTACK IS EMPTY\n");
else
{
for(i=(top-1);i>=0;i--)
{
if(i==(top-1))
printf("----> TOP ELEMENT\n");
printf("%d \n",stack[i]);
}
printf("\n");
}
}

void STACK_COUNT()
{
if(top<=0)
printf("STACK IS EMPTY\n\n");
else
{
printf("STACK IS EMPTY WITH %d ELEMENTS\n\n",(SIZE-(top-1)));
}
}

void EXIT()
{
exit(0);
}

Thursday, August 20, 2015

Mutual Exclusion

A way of making sure that if one process is using a shared modifiable data, the other processes will be excluded from doing the same thing.

Formally, while one process executes the shared variable, all other processes desiring to do so at the same time moment should be kept waiting; when that process has finished executing the shared variable, one of the processes waiting; while that process has finished executing the shared variable, one of the processes waiting to do so should be allowed to proceed. In this fashion, each process executing the shared data (variables) excludes all others from doing so simultaneously. This is called Mutual Exclusion.

Note that mutual exclusion needs to be enforced only when processes access shared modifiable data - when processes are performing operations that do not conflict with one another they should be allowed to proceed concurrently.

Mutual Exclusion Conditions:

If we could arrange matters such that no two processes were ever in their critical sections simultaneously, we could avoid race conditions. We need four conditions to hold to have a good solution for the critical section problem (mutual exclusion).

No two processes may at the same moment inside their critical sections.
No assumptions are made about relative speeds of processes or number of CPUs.
No process should outside its critical section should block other processes.
No process should wait arbitrary long to enter its critical section.

Linux Kernel

Linux Kernel

Linux kernel is the very basic thing which we should have in our hand. Kernel is the one which is doing scheduling, task management, memory management and input output management. When you are getting kernel means you are getting collection of modules which are doing all above mentioned tasks. Now question is what I will get if I am purchasing kernel from market

You will get kernel as a library. Some companies are selling source code of kernel but for that you have to pay more. And royalty is also involved with some proprietary kernels.

Linux Kernel Version Numbering

According to this website at the time of writing this article, kernel release version is 2.6.34.

Let us see what these numbers are, below is the description

-First number 2, represent linux version

-Second number 6, represent major revision-Third number 34, represent minor revision

If third number is odd, it means that this refer to unstable version and is under development. It means that when we are going to download kernel we should select those version which has even number at third place. For example v2.6.24 is stable release and 2.6.25 is unstable release.

Here in above screen shot you can see other versions like 2.6.35-rc3, this means that 2.6.35 is a stable kernel and is under development and will be next released. And rc-3 represent release candidate -3, so we can say that this is a prerelease version.

Why should we choose Linux OS?

The reasons why most of the people chose Linux OS for the embedded device are,

· Linux is a free and open source operating system

· Linux can run on various kind of CPUs

· Linux has a very well structured kernel

· Linux is a highly secure OS

· Linux OS never crash unless there is any hardware problems

· Easy to write device drivers in Linux kernel

· Wide range of software available which are supported by Linux

6 level stages of a typical Linux boot process

Press the power button on your system, and after few moments you see the Linux login prompt.

Have you ever wondered what happens behind the scenes from the time you press the power button until the Linux login prompt appears?

1. BIOS

BIOS stands for Basic Input/Output System

§ Performs some system integrity checks

§ Searches, loads, and executes the boot loader program.

§ It looks for boot loader in floppy, cd-rom, or hard drive. You can press a key (typically F12 of F2, but it depends on your system) during the BIOS startup to change the boot sequence.

§ Once the boot loader program is detected and loaded into the memory, BIOS gives the control to it.

§ So, in simple terms BIOS loads and executes the MBR boot loader.

2. MBR

§ MBR stands for Master Boot Record.

§ It is located in the 1st sector of the bootable disk. Typically /dev/hda, or /dev/sda

§ MBR is less than 512 bytes in size. This has three components 1) primary boot loader info in 1st 446 bytes 2) partition table info in next 64 bytes 3) mbr validation check in last 2 bytes.

§ It contains information about GRUB (or LILO in old systems).

§ So, in simple terms MBR loads and executes the GRUB boot loader.

3. GRUB

§ GRUB stands for Grand Unified Bootloader.

§ If you have multiple kernel images installed on your system, you can choose which one to be executed.

§ GRUB displays a splash screen, waits for few seconds, if you don’t enter anything, it loads the default kernel image as specified in the grub configuration file.

§ GRUB has the knowledge of the filesystem (the older Linux loader LILO didn’t understand filesystem).

§ Grub configuration file is /boot/grub/grub.conf (/etc/grub.conf is a link to this). The following is sample grub.conf of CentOS.

§ As you notice from the above info, it contains kernel and initrd image.

§ So, in simple terms GRUB just loads and executes Kernel and initrd images.

4. Kernel

§ Mounts the root file system as specified in the “root=” in grub.conf

§ Kernel executes the /sbin/init program

§ Since init was the 1st program to be executed by Linux Kernel, it has the process id (PID) of 1. Do a ‘ps -ef | grep init’ and check the pid.

§ initrd stands for Initial RAM Disk.

§ initrd is used by kernel as temporary root file system until kernel is booted and the real root file system is mounted. It also contains necessary drivers compiled inside, which helps it to access the hard drive partitions, and other hardware.

5. Init

§ Looks at the /etc/inittab file to decide the Linux run level.

§ Following are the available run levels

§ 0 – halt

§ 1 – Single user mode

§ 2 – Multiuser, without NFS

§ 3 – Full multiuser mode

§ 4 – unused

§ 5 – X11

§ 6 – reboot

§ Init identifies the default initlevel from /etc/inittab and uses that to load all appropriate program.

§ Execute ‘grep initdefault /etc/inittab’ on your system to identify the default run level

§ If you want to get into trouble, you can set the default run level to 0 or 6. Since you know what 0 and 6 means, probably you might not do that.

§ Typically you would set the default run level to either 3 or 5.

6. Runlevel programs

§ When the Linux system is booting up, you might see various services getting started. For example, it might say “starting sendmail …. OK”. Those are the runlevel programs, executed from the run level directory as defined by your run level.

§ Depending on your default init level setting, the system will execute the programs from one of the following directories.

§ Run level 0 – /etc/rc.d/rc0.d/

§ Run level 1 – /etc/rc.d/rc1.d/

§ Run level 2 – /etc/rc.d/rc2.d/

§ Run level 3 – /etc/rc.d/rc3.d/

§ Run level 4 – /etc/rc.d/rc4.d/

§ Run level 5 – /etc/rc.d/rc5.d/

§ Run level 6 – /etc/rc.d/rc6.d/

§ Please note that there are also symbolic links available for these directory under /etc directly. So, /etc/rc0.d is linked to /etc/rc.d/rc0.d.

§ Under the /etc/rc.d/rc*.d/ directories, you would see programs that start with S and K.

§ Programs starts with S are used during startup. S for startup.

§ Programs starts with K are used during shutdown. K for kill.

§ There are numbers right next to S and K in the program names. Those are the sequence number in which the programs should be started or killed.

§ For example, S12syslog is to start the syslog deamon, which has the sequence number of 12. S80sendmail is to start the sendmail daemon, which has the sequence number of 80. So, syslog program will be started before sendmail.