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Problem With 24LC256 & Atmega16 Read/write & Strange Wave Form On Rigol DS1054Z

Praveen Sharma Norway

Hardware: ATmega16 Running At 4 MHz Connected With Breadboard Software: C Project Using Atmel IDE Ver 7


I am very beginner to electronics.
I have experience with software development but no experience with electronics.
I have learned everything on my own from last 3-4 months.

I am trying to write to and read from 24LC256 chip with Atmega16.
In my program I don't get any error , program runs good but I don't read what I write I always read 0xFF which is default value.

So to find out more about this I actually bought an Rigol DS1054Z and, after connecting probes to SDA & SCL (with pin and GND) I get a very strange wave form, I have attached a picture of the wave form.

I expected to see a wave form which has a straight line and then goes low or high, I mean same which we see on images where we learn about I2C protocol.

I can try whatever you guys think may go wrong.

Please help me in finding/troubleshoot the problem.
Thanks in advance.


Problem with 24LC256 & Atmega16 read/write & strange wave form on Rigol DS1054Z


#ifndef F_CPU					// if F_CPU was not defined in Project -> Properties
#define F_CPU 2000000UL			// define it now as 2 MHz unsigned long

#include <avr/io.h>
#include "util/delay.h"

#define EEPROM_WRITE 0xA0
#define EEPROM_READ 0xA1

void i2c_init()
	//set SCL to 100kHz
	// CPU freq = 2MHz
	TWSR = 0x00;
	TWBR = (1<<TWPS1);
	//enable TWI
	TWCR = (1<<TWEN);

void i2c_start()
	TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);
	while ((TWCR & (1<<TWINT)) == 0);

void i2c_stop()
	TWCR = (1<<TWINT)|(1<<TWSTO)|(1<<TWEN);

void i2c_write(uint8_t u8data)
	TWDR = u8data;
	TWCR = (1<<TWINT)|(1<<TWEN);
	while ((TWCR & (1<<TWINT)) == 0);

uint8_t i2c_read()
	TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWEA);
	while ((TWCR & (1<<TWINT)) == 0);
	return TWDR;

int main()
	uint8_t readByte=0;
	uint16_t address=0x0;
	uint8_t writeVal=0;
	while (1)
		i2c_write(address & 0xFF);
		//for (int a =0;a<128;a++)
		i2c_write(address & 0xFF);
		readByte =i2c_read();
	return 0;


R Avinash Gupta
2017-05-01 02:30:16
Please attach proteus schematic file ...

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