master and slave Microcontrollers

[garg29]

writei2c(0xa1

I'm trying to design a project just for hobby.
Project is suppose i have to mesaure some physical
property let's say temperature of 10 different
locations each situated nearby only. i have to use
slave and master method as i have drawn in picture
below. what method should i follow for programming.
I'll be really thankful if someone can please provide
just brief example on this.

Thanks in advance.

Garg

 

[mrcube_ns]

slave writei2c

In this situations I use modbus (or mechanisams of modbus) or something similar (I do this on PLC's).

Master should put message:
ABCD
A - master address e.g. 01h
B - slave address e.g. 04h (third slave mcu)
C - command (give me temperature, or comething else, or put output pin 1 to "1" or ....), e.g. 01h give temp, 02h give time, 03h set output1 ....
D - checksum (there are many types of CS, so choose one...

Slave's should give answer:
ABCDE

A - slave address
B - master address (01h)
C - number of bytes which slave sending
D - data (C number of bytes data)
E - checksum

Regards,

Mr.Cube

 

[garg29]

Thanks Mr.Cube. Should i use SCL & SDA type two wire link for whole network(as i have drawn). Sorry if it's too basic....i'm new to communications

 

[mrcube_ns]

Generaly,

You always can use i2c, it's made for this kind of communication (master - slaves).

I think you can find lots examples and codes on edaboard.

Best regards.

Mr.Cube

 

[garg29]

i2c reminds me of ds1307 rtc chip which i tried to commnicate with 89c51 i did but with PIC microcontroller i was unsuccessful. With eeprom 24cxx i have done again with 89c uCs will i need to take same method as in the code attached

Thanks........with best regards.
Garg

#include<reg52.h>
#include<intrins.h>


#define ACK		1
#define NO_ACK	0


unsigned char i2;


sbit SDA  =  P1^7;	// connect to SDA pin (Data)
sbit SCL  =  P1^6;	// connect to SCL pin (Clock)



//-------------------------------
// start I2C
//-------------------------------
void Start(void)
{
    SDA = 1;
	SCL = 1;
	_nop_();_nop_();
	SDA = 0;
	_nop_();_nop_();
	SCL = 0;
	_nop_();_nop_();
}

//-------------------------------
// stop I2C
//-------------------------------
void Stop(void)
{
	SDA = 0;	    	
	_nop_();_nop_();
	SCL = 1;
	_nop_();_nop_();
	SDA = 1;	
}

//-------------------------------
// Write I2C
//-------------------------------
void WriteI2C(unsigned char Data)
{    

	for (i2=0;i2<8;i2++)
	{
        SDA = (Data & 0x80) ? 1:0;
		SCL=1;SCL=0;
		Data<<=1;
	}

  	SCL = 1; 
	_nop_();_nop_();
	SCL = 0;

}

//-------------------------------
// Read I2C
//-------------------------------
unsigned char ReadI2C(bit ACK_Bit)
{
    
    unsigned char Data=0;

    SDA = 1;	
	for (i2=0;i2<8;i2++)
	{
		SCL   = 1;		
		Data<<= 1;
		Data  = (Data | SDA);		
		SCL   = 0;
		_nop_();
	}
    
 	if (ACK_Bit == 1)
	SDA = 0; // Send ACK		
	else		
	SDA = 1; // Send NO ACK				

	_nop_();_nop_();
	SCL = 1;		
	_nop_();_nop_();
	SCL = 0;
	
	return Data;
}

//-------------------------------
// Read 1 byte form I2C
//-------------------------------
unsigned char ReadBYTE(unsigned int Addr)
{
   	unsigned char Data;
	Start();
	WriteI2C(0xA0);
	//WriteI2C((unsigned char)(Addr>>8)&0xFF);	// ....not valid for small EEPROMs
	WriteI2C((unsigned char)Addr&0xFF);
	Start();
	WriteI2C(0xA1);
	Data = ReadI2C(NO_ACK);
	Stop();
   	return(Data);
}

//-------------------------------
// Write 1 byte to I2C
//-------------------------------
void WriteBYTE(unsigned int Addr,unsigned char Data)
{
	Start();
	WriteI2C(0xA0);
	//WriteI2C((unsigned char)(Addr>>8)&0xFF);	// send address high....not valid for small EEPROMs
	WriteI2C((unsigned char)Addr&0xFF);			// send address low	
	WriteI2C(Data);
	Stop();	
}

 

[mrcube_ns]

Here some i2c code examples.

Help yourself.