Simple SPI Blink Tutorial??

Projects Networking, Protocols, and Devices
1

Hello,

I am attempting to learn how to control an ATMega328 IC from my ATMega2560 Arduino using SPI.

I have found the various tutorials that use digital potmeters, but I have no digital potmeters and all I want to learn to do is blink an LED on the ATMega328 from the code running on ATMega2560 via SPI.

Can anyone please provide a few lines of code to show me how this is done?

Here is my pin configuration (using Arduino pin names for both ICs):

ATMega2560 pin 50 (MISO) => ATMega328 pin 12 (MISO)
ATMega2560 pin 51 (MOSI) => ATMega328 pin 11 (MOSI)
ATMega2560 pin 52 (SCK) => ATMega328 pin 13 (SCK)
ATMega2560 pin 2 => ATMega328 pin 10 (SS)

ATMega2560 5V pin => ATMega328 Vcc pin
ATMega2560 GND pin => ATMega328 GND pin

ATMega328 pin 3 => LED that I would like to blink

Here is my current code:

#include "SPI.h" // necessary library

int SLAVESELECT = 2;
int DATAOUT = 51;
int DATAIN = 50;
int SPICLOCK = 52;

void setup()
{
pinMode(DATAOUT, OUTPUT);
pinMode(DATAIN, INPUT);
pinMode(SPICLOCK, OUTPUT);
pinMode(SLAVESELECT, OUTPUT);

SPI.begin(); // wake up the SPI bus.
SPI.setBitOrder(MSBFIRST);
}

void setValue(int pin, int value)
{
digitalWrite(SLAVESELECT, LOW);
SPI.transfer(pin); // send command byte
SPI.transfer(value); // send value (0~255)
digitalWrite(SLAVESELECT, HIGH);
}

void loop()
{
setValue(0x11,255);
delay(1000);
setValue(0x11,0);
delay(1000);
}

2 
#include "SPI.h" // necessary library

int SLAVESELECT = 2;

void setup()
{
  pinMode(SLAVESELECT, OUTPUT);

  SPI.begin(); // wake up the SPI bus.
  SPI.setBitOrder(MSBFIRST);
}

void setValue(int pin, int value)
{
  digitalWrite(SLAVESELECT, LOW);
  SPI.transfer(pin); // send command byte
  SPI.transfer(value); // send value (0~255)
  digitalWrite(SLAVESELECT, HIGH);
}

void loop()
{
  setValue(0x11,255);
  delay(1000);
  setValue(0x11,0);
  delay(1000);   
}

That looks OK (no need to set pin modes for SPI pins) but the hard part is the slave side. I think you will have to handle the SPI input interrupt on your own. I'm pretty sure the SPI library doesn't cover slave mode.

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