Need help

**Ahmed El-Wakil** · 05-26-2016

i'm trying to scan array of bytes from a keypad, display it on LCD and then send it from atmega32 to another atmega32 using UART. excuse me if there is a fatal mistakes i'm a bit newbie.

Code:

#include <avr/io.h>
# define F_CPU 1000000UL
#include "BASICTYPES.h"
#include "util/delay.h"
#include "keypad.h"
#include "LCD.h"
#include "UART.h"




void send_password(void);




int main(void)
{ 
    keypad_init();
    
    LCD_init();
    
    UART_Init();
    
    while(1)
    {
    
        send_password();
        
        
    }
    
    
    
}




void send_password(void)
{
    u8 k=0,l=0,c=0,cond;
    
    u8 *passw;
    LCD_print("Enter password");
    LCD_goto(4,2);
    
    while(1)
    {
        
        k=keypad_read();
        
        _delay_ms(50);
        
        if (k)
        {  
            passw[l]=k;
            LCD_data(k);
            k=0;
            _delay_ms(50);
            l++;
        
           if (l==4)
            {break;}
                    
                 
        }
        _delay_ms(50);
    }
    
    
    
        for (c=4;c>0;c--)
        {
            UART_SendByte(passw[4-c]);
            _delay_ms(10);
        }


        
    
    


    while (UART_ReciveData()!=0)
    {
        cond=UART_ReciveData();
        if (cond==0X01)
        {
            
            LCD_goto(0,2);
            LCD_print("Correct password");
            
        }
        else if (cond==0X02)
        {
            
            LCD_goto(0,2);
            LCD_print("Wrong password");
        }
    }
    
}

**Salem** · 05-26-2016

> u8 *passw;
This isn't pointing at any valid memory.
It's easy to use a 4 byte array here.

> cond=UART_ReciveData();
> if (cond==0X01)
How does this check that the received character is what you want?

> then send it from atmega32 to another atmega32 using UART
Then you need TWO programs.
- One does the read and transmit.
- The other does the receive, check and print

**Ahmed El-Wakil** · 05-27-2016

thanks alot, making it an array of 4 bytes solved a bit of the problem but the code still can't do the what i want and sure i have two codes on two microcontrollers here is the receiver code

Code:

#include <avr/io.h>
#include "UART.h"
#include "BASICTYPES.h"
#include "EEPROM_Driver.h"
# define F_CPU 1000000UL


void stor_pass_eeprom(void);
void compare_passes(void);


u8 password[4]="5555";


u8 crct_pass_flag;




int main(void)
{
    
    
    UART_Init();
    
    
    while(1)
    { 
        stor_pass_eeprom();
        
        compare_passes();
        
        
    }
}






void stor_pass_eeprom(void)
{
    u16 i;
    for(i=4;i>0;i--)
    {
        EEPROM_Write((4-i),password[i]);
    }
}


void compare_passes(void)
{ u8 rx_pass[4],z=0;
    
    while(UART_ReciveData()!=0)
    {
        rx_pass[z]=UART_ReciveData();
        z++;
        if(z==4)
        {
            break;
        }
    }
    
        if(rx_pass==password)
        {
            UART_SendByte(0X01);    
        }
     
    
      else  
        {
        
               UART_SendByte(0X02);    
        
         }
         
    
    
}

**Salem** · 05-27-2016

Some points.
1. Learn to indent code consistently -> Indent style - Wikipedia, the free encyclopedia
Your code is short, but already its hard to read.

2. Not sure why you like running loops backwards.
> for(i=4;i>0;i--)
> EEPROM_Write((4-i),password[i]);
But you have managed to achieve a buffer overrun in the process.

3. This will read every other character.
> while(UART_ReciveData()!=0)
> rx_pass[z]=UART_ReciveData();
Try
u8 ch;
// read a char from the UART, assign it to ch, and compare it with zero
while ( (ch=UART_ReciveData())!=0)
rx_pass[z] = ch;

> if(rx_pass==password)
This is not how you compare strings. Use strcmp()
Further, neither password nor rx_pass has a \0 character, so perhaps you need strncmp() instead.

**Ahmed El-Wakil** · 05-27-2016

i'm sorry for the bad code. i think i read that it's a better practice to use backward loops but not sure. i'm searching for what buffer overrun is, but here is what i tried to do but also didn't work.

Code:

#include <avr/io.h>
#include "UART.h"
#include "BASICTYPES.h"
#include "EEPROM_Driver.h"
# define F_CPU 1000000UL


void stor_pass_eeprom(void);
void compare_passes(void);


u8 password[4]="5555";








int main(void)
{
    
    
    UART_Init();
    
    
    while(1)
    { 
        //stor_pass_eeprom();
        
        compare_passes();
        
        
    }
}






/*void stor_pass_eeprom(void)
{
    u16 i;
    
    for(i=4;i>0;i--)
    {
        EEPROM_Write((4-i),password[i]);
    }
}*/


void compare_passes(void)
{
       u8 rx_pass[4],z=0,ch=0;
    
    
        while ((ch=UART_ReciveData())!=0)
        {
              rx_pass[z]=ch;
              z++;
              if(z==4)
              {
                   break;
              }
        }
          
 
        if(strcmp(rx_pass,password))
       {
                  UART_SendByte(0X01);    
       }
       else  
       {
                  UART_SendByte(0X02);        
            }    
}

**Salem** · 05-27-2016

Like I said, use strncmp because strcmp relies on a \0, and neither of your arrays (rx_pass or password) as a \0

**megafiddle** · 05-27-2016

Some processors have a "decrement and branch on not zero" instruction.
On these, the assembly code could be more efficient if the loop counted down to zero.

-

**Salem** · 05-27-2016

Originally Posted by megafiddle

Some processors have a "decrement and branch on not zero" instruction.
On these, the assembly code could be more efficient if the loop counted down to zero.

-

True enough, but we're writing in a high level language, so we shouldn't be second-guessing what the compiler will do.
The first order of business is to write clear and simple code, so
- you can easily understand it
- through clarity of understanding, there is less chance of subtle bugs (as aptly demonstrated already - attempting to be smart has back-fired)
- gives the compiler the best chance to optimise it without having to unpick needless obfuscation.

Indexing an array backwards could play havoc with data cache prediction logic, which may assume that linear access is forwards through memory.

**Ahmed El-Wakil** · 05-29-2016

after hundred of trials i found that i have a problem with my uart driver which i copied from the data sheet, i'm trying to make the most simple send and receive commands but it's not working. i would highly appreciate it if anyone can help me cuz i'm about to get mad

.

UART DRIVER

Code:

#include <avr/io.h>
#include "BASICTYPES.h"


#define BAUD_PRESCALE 25




void UART_Init(void)
{
   UBRRL = BAUD_PRESCALE;
   UBRRH = (u8)(BAUD_PRESCALE>>8);
   UCSRB=(1<<TXEN)|(1<<RXEN);
   UCSRC = (1<<URSEL)|(1<<USBS)|(3<<UCSZ0);
}
 void UART_SendByte(u8 Data)
{
	while(! (UCSRA & (1<<UDRE)));
		
	UDR=Data;
}
u8 UART_ReciveData(void)
{
	
	while(!(UCSRA & (1<<RXC)));
	
	 return UDR;
	
}
void USART_Flush( void )
{
	unsigned char dummy;
	while ( UCSRA & (1<<RXC) ) dummy = UDR;
}

first uc

Code:

int main(void)
{
    keypad_init();
    LCD_init();
    UART_Init();
    _delay_ms(100);
    
    while(1)
    {
        UART_SendByte(k);
		_delay_ms(100);
        l=UART_ReciveData();
		if (l==CORRECT_PASSWORD)
		{
			LCD_print("yes");
		}
		else if(l==WRONG_PASWORD)
		{
			LCD_print("no");
		}
    }
}

second uc

Code:

int main(void)
{
	UART_Init();
	_delay_ms(100);


	while(1)
	{
		
		
		g=UART_ReciveData();
		_delay_ms(100);
		if (g==5)
		{
	    	UART_SendByte(CORRECT_PASSWORD);
		}
		else
		{
		    UART_SendByte(WRONG_PASWORD);
		}
		
	   
	}
}

**Salem** · 05-30-2016

atmega32 - Google Search
The first experiment is to make the 2nd controller just do this

Code:

while ( 1 ) {
  // just echo everything back
  UART_SendByte(UART_ReciveData());
}

And make the first controller do this

Code:

for ( ch = ' ' ; ch <= '~' ; ch++ ) {
  UART_SendByte(ch);
  rxch = UART_ReciveData();
  LCD_print(rxch);
  _delay_ms(100);
}

When you see a steady alphabet appear on screen, you know you have a working round trip communication.

**Ahmed El-Wakil** · 05-31-2016

nothing appeared on the screen and i still couldn't find what's wrong with the driver, i'm using proteus btw could it be the reason?

**Salem** · 05-31-2016

What is 'proteus'?
Your IDE - I doubt that would have any effect.
A tiny OS on your devices - possibly.

**Ahmed El-Wakil** · 05-31-2016

Proteus is the simulation tool that i'm using to simulate the project , also Atmel studio is my IDE.using windows 10 as an OS

**Salem** · 05-31-2016

Do you have any example codes which use the serial port?
Have you tried them on the simulator?
Do they work?

**Ahmed El-Wakil** · 05-31-2016

no i don't have any it's my first try to use serial port .i didn't but it's working with a friend using different version of the program. he uses the same driver and yes it's working perfect.

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