SPI master

SPI_master.ino

/*
  Florin Simedru
  Complete project details at https://blog.automatic-house.ro
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files.
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
*/
/*
PlatformIO Project Configuration File;
;
Build options : build flags, source filter;
Upload options : custom upload port, speed and extra flags;
Library options : dependencies, extra library storages;
Advanced options : extra scripting;
; Please visit documentation for the other options and examples
;
https : // docs.platformio.org/page/projectconf.html

[env:uno] 
platform = atmelavr
board = uno
framework = arduino
upload_port = COM8
monitor_port = COM8
monitor_speed = 115200
*/

#include <Arduino.h>
#include <SPI.h>
byte  transferAndWait(const byte what);

void setup(void)
{
  Serial.begin(115200);
  Serial.println();
  digitalWrite(SS, HIGH); // ensure SS stays high for now
  SPI.begin();
  // Slow down the master a bit
  SPI.setClockDivider(SPI_CLOCK_DIV8);
} // end of setup

byte transferAndWait(const byte what)
{
  byte a = SPI.transfer(what);
  delayMicroseconds(80);
  return a;
} // end of transferAndWait

void loop(void)
{
  byte a, b;
  // enable Slave Select
  digitalWrite(SS, LOW);

  transferAndWait(0);
  b = transferAndWait(0);
  a = transferAndWait(0);

  // disable Slave Select
  digitalWrite(SS, HIGH);
  Serial.println(a, DEC);

  delay(200); // 0.100 second delay
} // end of loop