Carry on HF screaming

Preamble

I bought a 433MHz transmitter/receiver pair on eBay for 57p.

433MHz Receiver/Transmitter pair

This has definitely been one of my cheapest purchases to date. However, I was at a bit of a loss as to what to do with them. So, I idly looked for some youtube video tutorials.

Video tutorials

A brief, but succinct, video introduction to using the 433MHz transmitter/receiver pair in conjunction with a pair of Arduinos.

Shows that a 433MHz signal requires a 173mm quarter wave dipole, as well as recommending the RadioHead Packet Radio library.

This video, which is part of a series from EEEnthusiast, shows the transmitter/receiver pair being used without an Arduino, which is interesting. Also, some useful code displaying the signals received from the receiver.

Bringing it all together

Now, by combining Julian Ilett‘s code from Arduino Nokia 5110 LCD Tutorial #3 – Live Numerical Data, with the code from Arduino Tut. #8 – Wireless RF Links Tutorial & Noise Reduction, the video tutorial above, you end up with

/*
Original code from https://www.youtube.com/watch?v=cwsCxUhHbQM 
Julian Ilets
433MHz/Certainty code from https://www.youtube.com/watch?t=370&v=RHJVyMYJ1XQ
*/

// For Nano Expansion Shield
/*
#define RST 12
#define CE  11
#define DC  10
#define DIN  9
#define CLK  8
*/

// For Leonardo Joystick Shield with blue LCD
/*
#define RST 9
#define CE  10
#define DC  11
#define DIN  12
#define CLK  13
*/
// For Leonardo Joystick Shield with Red
#define RST 12
#define CE  13
#define DC  11
#define DIN  10
#define CLK  9

#define PROBE_PIN A0

#define LED_PIN 13

#include "font.h";

int certainty = 0;

void LcdWriteString(char *characters)
{
  while(*characters) LcdWriteCharacter(*characters++);
}

void LcdWriteCharacter(char character)
{
  for(int i=0; i<5; i++) LcdWriteData(ASCII[character - 0x20][i]);
  LcdWriteData(0x00);
}

void LcdWriteData(byte dat)
{
  digitalWrite(DC, HIGH); //DC pin is low for commands
  digitalWrite(CE, LOW);
  shiftOut(DIN, CLK, MSBFIRST, dat); //transmit serial data
  digitalWrite(CE, HIGH);
}

void LcdXY(int x, int y)
{
  LcdWriteCmd(0x80 | x);  // Column.
  LcdWriteCmd(0x40 | y);  // Row.
}

void LcdWriteCmd(byte cmd)
{
  digitalWrite(DC, LOW); //DC pin is low for commands
  digitalWrite(CE, LOW);
  shiftOut(DIN, CLK, MSBFIRST, cmd); //transmit serial data
  digitalWrite(CE, HIGH);
}

void setup()
{
  pinMode(RST, OUTPUT);
  pinMode(CE, OUTPUT);
  pinMode(DC, OUTPUT);
  pinMode(DIN, OUTPUT);
  
  pinMode(LED_PIN, OUTPUT);
  
  digitalWrite(RST, LOW);
  digitalWrite(RST, HIGH);
  
  LcdWriteCmd(0x21);  // LCD extended commands
  LcdWriteCmd(0xbf);  // set LCD Vop (contrast)
  LcdWriteCmd(0x04);  // set temp coefficent
  LcdWriteCmd(0x10);  // LCD bias mode 1:40
  LcdWriteCmd(0x20);  // LCD basic commands
  LcdWriteCmd(0x0C);  // LCD normal video
  
  for(int i=0; i<504; i++) LcdWriteData(0x00); // clear LCD LcdXY(0,2); LcdWriteString("VOLTAGE:"); } char string[8]; void loop() { float voltage = analogRead(PROBE_PIN) * 5.0 / 1024; LcdXY (50,2); LcdWriteString(dtostrf(voltage,5,2,string)); if (voltage > 4.75){
    certainty++;
  } else {
    certainty = 0;
  }
  if (certainty >= 4) {
    digitalWrite(LED_PIN, HIGH);
  } else {
    digitalWrite(LED_PIN, LOW);
  }
  delay(50); 
}

Load this on to the Leonardo, sporting a Joystick shield, as mentioned in Is your backlight pin in the wrong place?

Leonardo and Joystick shield with Nokia 5100 display and nRF24L01

Now, connect the output of the receiver to A0 on the Arduino, like so (Fritzing diagram omits the joystick shield, and LED on pin D13, for clarity),

433Mhz Receiver and Arduino

with the Transmitter circuit having a momentary push button between ATAD and Vcc

433Mhz Transmitter
Push button between Vcc and ATAD

you end up with a display on the LCD screen, in lieu of using the serial port, showing the received voltage, as well as the LED lighting up, upon the button press.

Note: The fritzing diagrams are taken from 433 MHz RF module with Arduino Tutorial 1