AVR SPI problem

[deveshsamaiya]

hello all...
I am trying to make a synchronous communication between two ATmega8 as Master and Slave. I using the following code with Fosc=1MHz internal RC. It is not working please help me....Please tell me what is wrong in this code???
SPI master code....

Code:

 
#include<avr/io.h>
#include<util/delay.h>
#include<compat/deprecated.h>
void SPI_masterinit(void)
{
  DDRB=0x32;    // MOSI, SS and SCK as output 
  SPCR=(1<<SPE)|(1<<MSTR)|(1<<SPR0)|(1<<SPR1);  // SPI enable, MASTER device, Fosc/128
  cbi(PORTB,2);
}

void SPI_master_transmit(unsigned char cdata)
{
 SPDR=cdata;
 while(!(SPSR & (1<<SPIF)));
}

int main(void)
{
  
  SPI_masterinit();
  
  while(1)
  { 
    
	SPI_master_transmit(0x01);
	
	
  }


  return 0;
}

SPI Slave code...

Code:

#include<avr/io.h>

void SPI_slave_init(void)
{
  DDRB=0x01;    // MISO as output
  SPCR=(1<<SPE);  // SPI enable, Slave device 
}

unsigned char SPI_slave_receive(void)
{
 while(!(SPSR & (1<<SPIF)));
 return SPDR;
}

int main(void)
{
  unsigned char rx_data;
  DDRC=0xFF;
  PORTC=0x00;
  SPI_slave_init();
  while(1)
  {
    rx_data=SPI_slave_receive(); 
    if(rx_data==0x01)  // If data received is 0x01
	PORTC=0xFF;          // LED at PORTC On
	if(rx_data==0x02)
	PORTC=0x00;
  }


  return 0;
}

[maduran]

"When the SPI is configured as a Slave, the Slave Select (SS) pin is always input. When SS is
held low, the SPI is activated, and MISO becomes an output if configured so by the user. All
other pins are inputs. When SS is driven high, all pins are inputs except MISO which can be user
configured as an output, and the SPI is passive, which means that it will not receive incoming
data. Note that the SPI logic will be reset once the SS pin is driven high.
The SS pin is useful for packet/byte synchronization to keep the Slave bit counter synchronous
with the master clock generator. When the SS pin is driven high, the SPI Slave will immediately
reset the send and receive logic, and drop any partially received data in the Shift Register."

The SS pin is driven low or high by the master.

[samir_1982]

Hi
sample code
http://winavr.kavirelectronic.ir

[yasir9909]

deveshsamaiya

apparently making two microcontrollers communicate with each other through SPI,one configured as master and the other configured as slave is quite simple...

You can simply use the code from data sheet of AVR (ATmega8) microcontroller

I would post the working models simulated in Protues later for you

At the moment you should study SPI port,including master slave configurations and corresponding C codes, from Data sheet of AVR (ATmega8) in detail

Why don't you use external crystal based oscillator?

[deveshsamaiya]

@yasir question...why dont you use external crystal based oscillator.??

Ya actually i can use that no problem at all. Is that can be a problem?? i studied the data sheet example codes also. that code wasnt working for slave side so i decided to use interrupt for SPI.

[yasir9909]

deveshsamaiya

well,i cannot be sure about SPI,however as far as i know about serial communication through UART,internal oscillator poses problems and is not considered as reliable as external stable crystal oscillator for serial communication...

may be internal oscillator could also pose such issues of stability and reliability for spi to spi communication...

Any ways,i have got the code for spi to spi communication between two ATmega32 microcontrollers and it has been compiled in ICC AVR compiler

Posted on: 16-11-2009, 10:26:47 - Automerged
here is the code for data transmission from master spi :

Code:

//ICC-AVR application builder : 4/16/2009 6:56:37 PM
// Target : M32
// Crystal: 11.059Mhz

#include <iom32v.h>
#include <macros.h>

#define cs 0x10

unsigned int timer0_counter=0,j=0;

void port_init(void)
{
 	 PORTA = 0x00;
 	 DDRA  = 0x03;
 	 PORTB = 0x00;
 	 DDRB  = 0x00;
 	 PORTC = 0x00; 
 	 DDRC  = 0x00;
 	 PORTD = 0x00;
 	 DDRD  = 0x00;
}

//TIMER0 initialize - prescale:1024
// WGM: Normal
// desired value: 100Hz
// actual value: 100.933Hz (0.9%)
void timer0_init(void)
{
     TCCR0 = 0x00; //stop
 	 TCNT0 = 0x95; //set count
 	 OCR0  = 0x6B;  //set compare
 	 TCCR0 = 0x05; //start timer
}

#pragma interrupt_handler timer0_ovf_isr:iv_TIM0_OVF
void timer0_ovf_isr(void)
{
 	 TCNT0 = 0x95; //reload counter value
	 
	 timer0_counter++;
	 if(timer0_counter==2)
	 {
	    PORTA^=0x03;
		timer0_counter=0;
	     
	 }
}

//SPI initialize
// clock rate: 2764749hz
void spi_init(void)
{
 	 SPCR = 0x50; //setup SPI - SPE,MSTR,
 	 SPSR = 0x00; //setup SPI
	 
	 //PORTB=(1<<PORTB4)|(1<<PORTB5)|(1<<PORTB7);
	 PORTB=(1<<PB4)|(1<<PB5)|(1<<PB7);
	 DDRB=(1<<DDB4)|(1<<DDB5)|(1<<DDB7);
}

void SPI_MasterTransmit(char cData)
{
 	 /* Start transmission */
	 SPDR = cData;
	 /* Wait for transmission complete */
	 while(!(SPSR & (1<<SPIF)))
	 ;
}


//UART0 initialize
// desired baud rate: 57600
// actual: baud rate:57599 (0.0%)
void uart0_init(void)
{
 	 UCSRB = 0x00; //disable while setting baud rate
 	 UCSRA = 0x00;
 	 UCSRC = BIT(URSEL) | 0x06;
 	 UBRRL = 0x0B; //set baud rate lo
 	 UBRRH = 0x00; //set baud rate hi
 	 UCSRB = 0x18;
}

//call this routine to initialize all peripherals
void init_devices(void)
{
 	 //stop errant interrupts until set up
 	 CLI(); //disable all interrupts
 	 port_init();
 	 timer0_init();
 	 spi_init();
 	 uart0_init();

 	 MCUCR = 0x00;
 	 GICR  = 0x00;
 	 TIMSK = 0x01; //timer interrupt sources
 	 SEI(); //re-enable interrupts
 	 //all peripherals are now initialized
}

//
void main(void)
{
     init_devices();
 	 //insert your functional code here...
	 while(1)
	 {
	       PORTB &=~cs;
	       SPI_MasterTransmit( 'a' );
	       PORTB |=cs;
		   
		   
	 }
}

And this is the code SPI slave:

Code:

//ICC-AVR application builder : 3/31/2009 1:09:34 PM
// Target : M32
// Crystal: 11.059Mhz

#include <iom32v.h>
#include <macros.h>

unsigned char spiData;

unsigned int k=0;

void port_init(void)
{
 	 PORTA = 0x00;
 	 DDRA  = 0x00;
 	 PORTB = 0x00;
 	 DDRB  = 0x00;
 	 PORTC = 0x00; 
 	 DDRC  = 0x03;
 	 PORTD = 0x00;
 	 DDRD  = 0x00;
}

//TIMER0 initialize - prescale:1024
// WGM: Normal
// desired value: 100Hz
// actual value: 100.933Hz (0.9%)
void timer0_init(void)
{
 	 TCCR0 = 0x00; //stop
 	 TCNT0 = 0x95; //set count
 	 OCR0  = 0x6B;  //set compare
 	 TCCR0 = 0x05; //start timer
}

#pragma interrupt_handler timer0_ovf_isr:iv_TIM0_OVF
void timer0_ovf_isr(void)
{
 	 TCNT0 = 0x95; //reload counter value
}

//SPI initialize
// clock rate: 2764749hz
void SPI_SlaveInit(void)
{	 
	 PORTB=(1<<PB6);
 	 SPCR = 0x40; //setup SPI
 	 SPSR = 0x00; //setup SPI
}

char SPI_SlaveReceive(void)
{
 	 /* Wait for reception complete */
	 while(!(SPSR & (1<<SPIF)))
	 ;
	 /* Return data register */
	 return SPDR;
}

//UART0 initialize
// desired baud rate: 57600
// actual: baud rate:57599 (0.0%)
void uart0_init(void)
{
 	 UCSRB = 0x00; //disable while setting baud rate
 	 UCSRA = 0x00;
 	 UCSRC = BIT(URSEL) | 0x06;
 	 UBRRL = 0x0B; //set baud rate lo
 	 UBRRH = 0x00; //set baud rate hi
 	 UCSRB = 0x18;
}

//call this routine to initialize all peripherals
void init_devices(void)
{
 	 //stop errant interrupts until set up
 	 CLI(); //disable all interrupts
 	 port_init();
 	 timer0_init();
 	 SPI_SlaveInit();
 	 uart0_init();

 	 MCUCR = 0x00;
 	 GICR  = 0x00;
 	 TIMSK = 0x01; //timer interrupt sources
 	 SEI(); //re-enable interrupts
 	 //all peripherals are now initialized
}


void USART_Transmit( unsigned char data )
{
 	 /* Wait for empty transmit buffer */
	 while ( !( UCSRA & (1<<UDRE)) )
	 ;
	 /* Put data into buffer, sends the data */
	 UDR = data;
}

//
void main(void)
{
 	 init_devices();
 	 //insert your functional code here...
 	 while(1)
	 {
 	       spiData=SPI_SlaveReceive();		 
	 	   		   
		   	   
		   if( (k%32)==0 )
		   {
		        USART_Transmit( '\r' );USART_Transmit( '\n' );
		   }
		   k++;
		   
		   USART_Transmit( spiData );
		   
		   //USART_Transmit( 70 );
	 }
}

This is quite simple code set,one microcontroller (master) sends a character 'a' continuously to the other microcontroller (slave) through SPI.The microcontroller which receives data from master displays it on virtual terminal through serial port

This is just tom give an idea how you can do spi-to-spi communication in master-slave mode



Posted on: 16-11-2009, 10:38:37 - Automerged
Here is the proteus simulation file named 'SPI32SPI32', for the above codes,attached with this post

[wellnerson1]

Hai deveshsamaiya,
 The problem in your coding is resolved. There is no much problem in your code. Only problem is you have to set the data direction register of port B (DDRB) properly in master mode coding. The modification is DDRB=0x2C;. Also ihave added the following code snippet in the while loop for blinking the leds._delay_ms(1);SPI_master_transmit(0x02);. The entire coding is attached in this message. Also check the fuse bit for atmega8 reset pin, otherwise the led connected in this pin will not blink.
With regards.