spi_adventures.ino

#define clockPin 13
#define MISO 12
#define MOSI 11
#define SS 7

void setup()
{
  pinMode(clockPin, OUTPUT);
  pinMode(MISO, INPUT);
  pinMode(MOSI, OUTPUT);
  pinMode(SS, OUTPUT);
  digitalWrite(SS, HIGH); //ready to pull low for transmission
}


// loop to repeatedly send byte "10101110" to slave device over SPI.


void loop()
{
  digitalWrite(SS, LOW); //enable slave
  delay(100); 
  
  digitalWrite(clockPin, LOW); //clock edge low
  digitalWrite(MOSI, HIGH); //send bit "1"
  digitalWrite(clockPin, HIGH); //slave reads bit on transition from low to high
  
  digitalWrite(clockPin, LOW); //set clock back low
  digitalWrite(MOSI, LOW); //send next bit "0"
  digitalWrite(clockPin, HIGH); //slave reads bit "0"
  
  digitalWrite(clockPin, LOW); //clock edge low
  digitalWrite(MOSI, HIGH); //send bit "1"
  digitalWrite(clockPin, HIGH); //slave reads bit on transition from low to high
  
  digitalWrite(clockPin, LOW); //set clock back low
  digitalWrite(MOSI, LOW); //send next bit "0"
  digitalWrite(clockPin, HIGH); //slave reads bit "0"
  
  digitalWrite(clockPin, LOW); //clock edge low
  digitalWrite(MOSI, HIGH); //send bit "1"
  digitalWrite(clockPin, HIGH); //slave reads bit on transition from low to high
  
  digitalWrite(clockPin, LOW); //clock edge low
  digitalWrite(MOSI, HIGH); //send bit "1"
  digitalWrite(clockPin, HIGH); //slave reads bit on transition from low to high
  
  digitalWrite(clockPin, LOW); //clock edge low
  digitalWrite(MOSI, HIGH); //send bit "1"
  digitalWrite(clockPin, HIGH); //slave reads bit on transition from low to high
  
  digitalWrite(clockPin, LOW); //set clock back low
  digitalWrite(MOSI, LOW); //send next bit "0"
  digitalWrite(clockPin, HIGH); //slave reads bit "0"
  
  digitalWrite(SS, HIGH); //disable slave
  
  delay(1000);
  
}