I'm trying to implement an SPI protocol with multiple slaves. I'm currently working with only two slaves and a master. Each slave has their own button which the user can press. What I want to do is this: When the user presses a button, the respective slave will send an acknowledgement to the master and master will blink an LED indicating it has receives acknowledgement from that particular slave.
Here's my code so far:
Code for master:
#define F_CPU 1e6
#include <avr/io.h>
#include <util/delay.h>
#define ACK_Slave1 0x7D
#define ACK_Slave2 0x7E
#define MOSI_PIN DDB5
#define SCK_PIN DDB7
#define SLAVE_SELECT1 DDB4
#define SLAVE_SELECT2 DDB3
/**
* set SPI enable (SPE), set MC as master (MSTR)
* set serial clock freqeuncy (prescalar) = f_osc / 16 ; (SPR1 and SPI2X being 0 , f_osc --> internal clock/crystal frequency)
* MOSI, SCK & Slave Select as output
* We have to set SS as output for master
*/
void SPI_Master_Init(void){
DDRB |= (1 << MOSI_PIN) | (1 << SCK_PIN) | (1 << SLAVE_SELECT1) | (1 << SLAVE_SELECT2);
PORTB &= ~(1 << SLAVE_SELECT1);
PORTB &= ~(1 << SLAVE_SELECT2);
SPCR = (1 << SPE) | (1 << MSTR) | (1 << SPR0);
}
/**
* Load data in the buffer (SPI data register / shift register)
* Wait until data transmission is complete
* return received data
*/
unsigned char SPI_Transceiver(unsigned char data){
SPDR = data;
while(!(SPSR & (1 << SPIF)));
return SPDR;
}
int main(void){
SPI_Master_Init();
DDRD |= (1 << DDD0) | (1 << DDD1);
PORTD &= 0x00; // clear output
unsigned char data;
while (1) {
data = 0x00;
data = SPI_Transceiver('1');
if(data == ACK_Slave1){
PORTD |= (1 << DDD0);
_delay_ms(1000);
PORTD &= ~(1 << DDD0);
_delay_ms(1000);
}
if(data == ACK_Slave2){
PORTD |= (1 << DDD1);
_delay_ms(1000);
PORTD &= ~(1 << DDD1);
_delay_ms(1000);
}
}
_delay_ms(500);
}
Code for slaves:
#define F_CPU 1e6
#include <avr/io.h>
#include <util/delay.h>
#define ACK_Slave1 0x7D
#define ACK_Slave2 0x7E
#define MISO_PIN DDB6
#define SLAVE_SELECT DDB4
/**
* MISO as output
* enable SPI enable
*
*/
void SPI_Slave_init(void){
DDRB |= (1 << MISO_PIN);
SPCR = (1 << SPE);
}
/**
* Load data in the buffer (SPI data register / shift register)
* Wait until data transmission is complete
* return received data
*/
unsigned char SPI_Transceiver(unsigned char data){
SPDR = data;
while(!(SPSR & (1 << SPIF)));
return SPDR;
}
int main(void){
SPI_Slave_init();
DDRA &= ~(1 << DDA0);
PINA &= 0x00;
unsigned char data;
while (1) {
data = 0x00;
if(PINA & (1 << DDA0)){
data = SPI_Transceiver(ACK_Slave1); // will be changed to ACK_Slave2 for another slave
}
}
}
The problem is the LED connected at PD0 doesn't blink at all and when I press the button , the LED at PD1 blinks an extra time i.e , if I press it one time, it blinks twice. I've attached a pin diagram of my configuration. Please point out any error in the code or in the diagram. Any help would be appreciated.
