Unable to read slave data.

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ghoral

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What does data[7:0] mean??



Here , What does DATA[7:0] mean, Do I have to send just (char DATA) to i2c_write function or it should be like (char DATA =0x00).
 
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Re: What does data[7:0] mean??

Hi,

Data[7:0]= 8 bits of data
* data7, data6, data5....data0.

Klaus
 

Re: What does data[7:0] mean??

So we just send char data= 0x00 or it should be any specific address.
 

Re: What does data[7:0] mean??

Hi,

Are you aware, the we don't know
* what controller you use
* what I2C device you use
* what compiler you use
* what libraries you use
...

Klaus
 

Re: What does data[7:0] mean??

Assuming that the I2C address indicates that you are doing a write to the device, then you should be putting in whatever value you need to send to that device address.
Susan
 

Re: What does data[7:0] mean??

I am using Avr atmega 32 and MFRC522 and atmel studoo.
 
Last edited by a moderator:

Hi,
I am doing project on RFID MFRC522. I have done read and write cycle according to datasheet page 20. I have send device address, and Fifo register address(0x09 datasheet page 36) and 8 bit data. I have done according to cycle But I cannot read the data. I dont know where I am getting ERROR. I think I have used right registers address and function are also ok. 

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#define F_CPU 16000000UL
#include <avr/io.h> 
#include <string.h>
#include <inttypes.h>
 
#define  SDA PC0
#define SCL PC1
 
#include "Lcd.avr.h"
#include "I2C.avr.h"
#include "i2cmaster.h"
//#include "Rfid.h"
 
#define Write_Address 0x50 //slave addres
 
#define Register_Address 0x09 //fifo register address
 
#define I2c_write 0 //write bit
#define I2c_read 1 //read bit
 
char Data=0x00; //Data[7:0]
 
void Rfid_Start()
{
    i2c_init();
    i2c_start(Write_Address+I2c_write);
    i2c_write(Register_Address);
    i2c_write(Data);
    i2c_stop();
}
unsigned char Rfid_get_data()
{
    
    i2c_start(Write_Address+I2c_write);
    i2c_write(Register_Address);;
    _delay_ms(1);
    i2c_start(Write_Address+I2C_READ);
    Data = i2c_readAck();
    i2c_stop();
    return Data;
}
 
int main()
{
    
    DDRB = 0xFF;
    lcd_init();
    _delay_ms(100);
    LCD_String_xy(0,0);
    lcdprint("Show your card:");
    Rfid_Start();
    
    while(1) 
    {
        Rfid_get_data();
        LCD_String_xy(0,1);
    //  PORTB = 0xFF;
        lcd_int(Data);
    
    }
}
 
Last edited by a moderator:

Hi,

I have no experience with your library functions. But from standard I2C communication:

Code: 
unsigned char Rfid_get_data
    
    i2c_start(Write_Address+I2c_write);
    i2c_write(Register_Address);
    _delay_ms(1);
    i2c_start(Write_Address+I2C_READ); [COLOR="#FF0000"]--> here I expect I2C_repeated_start instead of I2C_start[/COLOR].
    Data = i2c_readAck();[COLOR="#FF0000"]--> here I expect to send a dummy byte 0xFF, then read the I2C_input_data_register[/COLOR].
Maybe your library functions do this correctly --> read the library documentation
Or look for verified code examples. I2C communication is almost independent from I2C_slave type, thus no need to look for a MFRC522 code.

Klaus
 

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