Published August 12, 2023 © GPL3+

ALS162 an alternative to DCF77 time radio with Arduino Uno

ALS162, as DCF77, are time radio transmitters in Europe. ALS162 has the advantage having an excellent immunity from electromagnetic noise

IntermediateFull instructions provided4 hours1,545

ALS162 an alternative to DCF77 time radio with Arduino Uno

Things used in this project

Hardware components

Arduino UNO

DFRobot I2C 16x2 Arduino LCD Display Module

quartz 10.368MHz

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

oscilloscope

Story

Before the world of the internet and GPS, the way to set the same time throughout a country was to use a radio station. There were at least 5 of these special radio stations in Europe until the 1990s, of which only 2 are still operating today: the very popular DCF77 in Germany and the rather unknown ALS162 in France.

DCF77 is a 50 kW, 77.5 kHz transmitter based at Mainflingen in Germany, detail can be found here: https://en.wikipedia.org/wiki/DCF77

ALS162 is a 800 kW, 162 kHz transmitter based at Allouis in France, detail are available here: in English https://en.wikipedia.org/wiki/ALS162_time_signal or in French https://syrte.obspm.fr/spip/services/ref-temps/article/mise-a-disposition-du-temps-legal-par-le-signal-als162

Both use similar time signal code sequence.

Most descriptions of time radio devices made or sold are based on DCF77. To make things easier for the do-it-yourselfer, there are also ready-made receiver modules for DCF77, made in China and very, very cheap...

Also, ALS162 is much less documented than DCF77, and can be considered more difficult to build, as it is a phase-modulated signal, while DCF77 is a very simple AM signal.

However, if you want to build your own receiver instead of using these ready-made modules, you will understand how hard it is to get the little LED to blink every second. Then it looks much easier to build a 162 kHz direct amplified receiver, as the power of the radio transmitter gives the ALS162 the advantage.

As DCF77 is modulated in AM, the first thought is that it is easy to handle, but it is also very sensitive to electromagnetic noise. So sensitive, in fact, that it is almost necessary to move the microprocessor used to decode and display the time away from the receiver, at the risk of interfering with the reception of the signal.

Instead, the ALS162, with its phase modulation method (very similar to FM), gains a very great advantage in terms of immunity to electromagnetic noise. Even all those modern LED lamps with their buck converters, as well as any device that requires a voltage converter power supply, are no longer a threat.

This manual explains step by step how to build an ALS162 receiver with its time decoder in the simplest way possible.

All files are available here: https://github.com/philippedc/ALS162-an-alternative-to-DCF77-time-radio-receiver-with-Arduino-Uno

Schematics

Code

horloge_ALS162-v0.9.ino

/*
 * ALS162 - Allouis (France) time broadcasted radio station decoder
 
  _________________________________________________________________
  |                                                               |
  |       author : Philippe de Craene <dcphilippe@yahoo.fr        |
  |       Free of use - Any feedback is welcome                   |
  _________________________________________________________________

  for ALS162 detail information: https://en.wikipedia.org/wiki/ALS162_time_signal
  


Materials:
 - 162kHz radio receiver
 - CD4046 PLL
 - ATmega328p with a 10368.000kHz Crystal Oscillator
 - LCD1602 with I2C 

Compiled with Arduino IDE v1.8.16

 *
 *                               ATmega328p
 * 
 *                    (RESET) PC6  1    28 PC5 (ADC5/SCL) = lcd1602 SCL
 *                      (RXD) PD0  2    27 PC4 (ADC4/SDA) = lcd1602 SDA
 *                      (TXD) PD1  3    26 PC3 (ADC3)
 *                     (INT0) PD2  4    25 PC2 (ADC2)
 *    freqOutPin = 11  (OC2B) PD3  5    24 PC1 (ADC1)
 *                   (XCK/T0) PD4  6    23 PC0 (ADC0)  A0 = dataInPin
 *                            VCC  7    22 AGND
 *                            GND  8    21 AREF 
 *     XTAL1    (XTAL1/TOSC1) PB6  9    20 AVCC
 *     XTAL2    (XTAL2/TOSC2) PB7 10    19 PB5         13 = blink led
 *                       (T1) PD5 11    18 PB4         12 = blink led
 *                     (AIN0) PD6 12    17 PB3 (OC2A) 
 *                     (AIN1) PD7 13    16 PB2         10 = activity led
 *  SecondSynchro = 8  (ICP1) PB0 14    15 PB1 (OC1A)   9 = MilliSynchro
 
 
Code versions
-------------

V0.9       11 Aug 2023     first full working version


 */


// parameters
#define VERSION         0.90     // code version
//#define DEBUG              1     // debug mode only

#define freqOut      162000L     // 162Khz clock generated for radio demodulation
#define freqCPU    10368000L     // note F_CPU still defined as 16000000 by Arduino IDE
#define offset             6     // serial data read offset: define sensibility

// pin definition
#define dataInPin          0     // analog read the instantaneous voltage of serial time data activity

// libraries call
#include <Wire.h>                // i2c communication
#include <LiquidCrystal_I2C.h>   // https://github.com/fdebrabander/Arduino-LiquidCrystal-I2C-library
LiquidCrystal_I2C lcd(0x27, 16, 2);

// variables
int dataIn = 512, memo_dataIn = 512;
unsigned int counter10ms = 0;         // 10ms counter during one minute
unsigned int counter100ms = 0;        // 100ms counter during one second
unsigned int noActivityCounter = 1;   // no activity 10ms counter to find the 59th second synchro
unsigned int secondsCounter = 0;      // simple counter for seconds
bool activity = true;                 // flag to detect the 59th second
bool memo_timeBit, timeBit = false;   // binary data
volatile bool synchro = false;        // 59th second detected
volatile bool bitHigh = LOW;          // flag HIGH data during the 2nd 100ms of each second    
volatile bool displayEnable = false;  // flag to enable update display
bool blinkLed = false;                // blinking led
bool runOnce = true;
byte minuteU = 0, minuteD = 0, hourU = 0, hourD = 0;
byte wday = 0, dayU = 0, dayD = 0, monthU = 0, monthD = 0, yearU = 0, yearD = 0;
String weekDay[] = { "Lun", "Mar", "Mer", "Jeu", "Ven", "Sam", "Dim" };
String months[] = { "Janv", "Fevr", "Mars", "Avri", "Mai ", "Juin",
                    "Juil", "Aout", "Sept", "Octo", "Nove", "Dece" };
bool holiday = false, summer = false;
bool parity1 = true, parity2 = true, parity3 = true;
byte bitHighCounter = 0;
bool testFullMinute = 0;
bool displayReady = false;

// special characters for LCD
uint8_t low[8]  = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1};   // single dot bottom right
uint8_t high[8]  = {0x1, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0};  // single dot top right


#ifdef DEBUG
 volatile unsigned int memo_counter10ms = 0;
 volatile unsigned int memo_secondsCounter = 0;
 volatile unsigned int minutesCounter = 0;
#endif

// port access definition
#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif


//
// setup
//____________________________________________________________________________________________

void setup() {

  DDRB = 0xFF;    // set all portB as output = PB0 to PB5, I/O 8 to 13, pins 14 to 19
  DDRD = 0xFF;    // set all portD as output = PD0 to PD5

// Set the timers 
//---------------------------------------------------------------------

  noInterrupts(); 

// set timer 1 to interrupt every 10ms (100Hz) used for ADC sampling rate
// Clear Timer on Compare Match (CTC) Mode
// precaler setting : freqCPU/8, N = 8
  TCCR1A = 0;
  TCCR1B = 0;
  TCCR1B = bit(WGM12) | bit(CS11);
  OCR1A  = ( freqCPU / 8L / 100L ) - 1;
  TIMSK1 = bit(OCIE1A);

// set timer 2 to get 162kHz clock on output 3
// from exemplers: http://www.gammon.com.au/timers 
  TCCR2A = 0;
  TCCR2B = 0;
  TCCR2A = bit(WGM20) | bit(WGM21) | bit(COM2B1);  // fast PWM, clear OC2A on compare
  TCCR2B = bit(WGM22) | bit(CS20);                 // fast PWM, no prescaler
  OCR2A = (freqCPU / freqOut) - 1;          // set the output signal frequency 
  OCR2B = ((OCR2A + 1) / 2) - 1;            // 50% duty cycle

  interrupts();

// change the ADC prescaler to 16 instead of 128 by default : 16x faster
// from examples: https://zestedesavoir.com/billets/2068/arduino-accelerer-analogread/
  sbi(ADCSRA, ADPS2);
  cbi(ADCSRA, ADPS1);
  cbi(ADCSRA, ADPS0);

// start the LCD display
  Wire.begin();
  Wire.setClock(400000);        // Change clock speed from 100k(default) to 400kHz
  lcd.begin();
  lcd.clear();
  lcd.createChar(0, low);       // special character declaration
  lcd.createChar(1, high);
  lcd.setCursor(0, 0);
  lcd.print("horloge ALS162");
  lcd.setCursor(0, 1);
  lcd.print("version v");
  lcd.print(VERSION);
  delay(1000);
  lcd.clear();
}

//
// loop
//____________________________________________________________________________________________

void loop() {

// once per second: display sequence
  if( displayEnable ) {
    if( runOnce ) {
      runOnce = false;    
      #ifdef DEBUG
       SecondSynchro(HIGH);              // make a debug signal each second I/O 8 pin 14
       lcd.setCursor(0, 0);
       lcd.print("                ");    // very much faster than lcd.clear()
       lcd.setCursor(0, 0);
       lcd.print(secondsCounter);
       lcd.setCursor(4, 0);
       lcd.print(bitHigh);
       lcd.setCursor(10, 0);
       lcd.print(memo_secondsCounter);
       lcd.setCursor(0, 1);
       lcd.print("                ");
       lcd.setCursor(0, 1);
       lcd.print(minutesCounter);
       lcd.setCursor(10, 1);
       lcd.print(memo_counter10ms);
      #else
       lcd.setCursor(6, 0);
       if( secondsCounter < 10 ) lcd.print("0");
       lcd.print(secondsCounter);
       lcd.setCursor(8, 0);
       if(bitHigh) lcd.write(1);
       else        lcd.write(0);
       switch( secondsCounter ) {
        case  0:
          if(displayReady) {
            lcd.setCursor(0, 0);
            if(parity2) { lcd.print(hourD); lcd.print(hourU); }
            else          lcd.print("--");
            lcd.print(":");
            if(parity1) { lcd.print(minuteD); lcd.print(minuteU); }
            else          lcd.print("--");
            lcd.print(":");
            lcd.setCursor(9, 0);
            if( summer )  lcd.print(" ete   ");
            else          lcd.print(" hiver ");
            lcd.setCursor(13, 0);
            if( holiday ) lcd.print("/fe");
            lcd.setCursor(0, 1);
            lcd.print("                ");
            lcd.setCursor(0, 1);
            if(parity3) {
              if( --wday >= 0 ) lcd.print(weekDay[wday]); lcd.print(" ");
              lcd.print((dayD *10) + dayU); lcd.print(" ");
              int monthN = (monthD *10) + monthU;
              if( --monthN >= 0 ) lcd.print(months[monthN]); lcd.print(" ");
              lcd.print((yearD *10) + yearU + 2000);
              if( dayD == 0 ) lcd.print(" ");  // to insure to cover the 16 characters of the line
            }
          }
          else {
            lcd.setCursor(0, 0);
            lcd.print("      00        ");
            lcd.print(secondsCounter);
            lcd.setCursor(0, 1);
            lcd.print("                ");
          }
          minuteU = 0; minuteD = 0; hourU = 0; hourD = 0;
          wday = 0; dayU = 0; dayD = 0; monthU = 0; monthD = 0; yearU = 0; yearD = 0;
          parity1 = true; parity2 = true; parity3 = true;
          bitHighCounter = 0;
          break;
        case  1:
          if( synchro ) testFullMinute = true;
          else          testFullMinute = false;
          break;
        case 14:
          holiday = bitHigh;
          break;
        case 17:
          summer = bitHigh;
          break;
        case 21:
        case 22:
        case 23:
        case 24:
          minuteU = minuteU | bitHigh << ( secondsCounter - 21 );
          if( bitHigh ) bitHighCounter++;
          break;
        case 25:
        case 26:
        case 27:
          minuteD = minuteD | bitHigh << ( secondsCounter - 25 );
          if( bitHigh ) bitHighCounter++;
          break;
        case 28:
          if((bitHighCounter %2) != bitHigh ) parity1 = false;
          bitHighCounter = 0;
          break;
        case 29:
        case 30:
        case 31:
        case 32:
          hourU = hourU | bitHigh << ( secondsCounter - 29 );
          if( bitHigh ) bitHighCounter++;
          break;
        case 33:
        case 34:
          hourD = hourD | bitHigh << ( secondsCounter - 33 );
          if( bitHigh ) bitHighCounter++;
          break;
        case 35:
          if((bitHighCounter %2) != bitHigh ) parity2 = false;
          bitHighCounter = 0;
          break;
        case 36:
        case 37:
        case 38:
        case 39:
          dayU = dayU | bitHigh << ( secondsCounter - 36 );
          if( bitHigh ) bitHighCounter++;
          break;
        case 40:
        case 41:
          dayD = dayD | bitHigh << ( secondsCounter - 40 );
          if( bitHigh ) bitHighCounter++;
          break;
        case 42:
        case 43:
        case 44:
          wday = wday | bitHigh << ( secondsCounter - 42 );
          if( bitHigh ) bitHighCounter++;
          break;
        case 45:
        case 46:
        case 47:
        case 48:
          monthU = monthU | bitHigh << ( secondsCounter - 45 );
          if( bitHigh ) bitHighCounter++;
          break;
        case 49:
          monthD = bitHigh;
          if( bitHigh ) bitHighCounter++;
          break;
        case 50:
        case 51:
        case 52:
        case 53:
          yearU = yearU | bitHigh << ( secondsCounter - 50 );
          if( bitHigh ) bitHighCounter++;
          break;
        case 54:
        case 55:
        case 56:
        case 57:
          yearD = yearD | bitHigh << ( secondsCounter - 54 );
          if( bitHigh ) bitHighCounter++;
          break;
        case 58:
          if(( bitHighCounter %2) != bitHigh) parity3 = false;
          break;
        case 59:
          synchro = false;
          if( testFullMinute ) displayReady = true;
          else                 displayReady = false;
          break;
       }  // end of switch
      #endif
      
      secondsCounter++;
      blinkLed = !blinkLed;
      BlinkingLed( blinkLed, synchro );
    }    // end test runOnce
  }      // end test displayEnable

  else  {
    runOnce = true;
    #ifdef DEBUG
     SecondSynchro(LOW);
    #endif
  }
}        // end of loop

//============================================================================================
// list of functions
//============================================================================================

//
// Interrupt function run every 10ms
//____________________________________________________________________________________________

ISR(TIMER1_COMPA_vect) {

// set times counters
  counter10ms ++;                          // count from 0 to ~6040 during 1 minute
  counter100ms = (counter10ms / 10) % 10;  // count from 0 to 9 for each second

// check demodulated radio signal
  memo_timeBit = timeBit;
  memo_dataIn = dataIn;  
  dataIn = analogRead( dataInPin );
  if(dataIn < memo_dataIn - offset) {
    timeBit = HIGH;
    noActivityCounter = 0;
  }
  else {
    timeBit = LOW;
    noActivityCounter++;
  }

// translate signal to bits
  if( counter100ms == 0 ) {
    if( timeBit ) { 
      ActivityLed(HIGH); 
    }
    else ActivityLed(LOW);
  }
  else if( counter100ms == 1 ) {
    if( timeBit ) { 
      ActivityLed(HIGH); 
      if( !memo_timeBit ) bitHigh = HIGH;  // only here there is the interesting data
    }
    else ActivityLed(LOW);
  } 

// update display enable moment
  else if( counter100ms == 2 ) displayEnable = true;
  else {
    bitHigh = LOW;
    displayEnable = false;
  }

// detect a full second with no activity = 59th second to start teh synchro
  if( noActivityCounter > 99 ) activity = false;
  if( !activity && (noActivityCounter == 0)) {
    activity = true;
    synchro = true;   
    #ifdef DEBUG
     memo_counter10ms = counter10ms;
     memo_secondsCounter = secondsCounter;
     minutesCounter++;
    #endif
    counter10ms = 0;
    secondsCounter = 0;
  }    // end of test !activity

// make a debug signal each 10ms I/O 9 pin 15
  #ifdef DEBUG
   static bool half = false;
   half = !half;
   if( half ) MilliSynchro(HIGH);
   else       MilliSynchro(LOW);
  #endif
}

//
// ActivityLed() = function to drive activity led
//____________________________________________________________________________________________

void ActivityLed( bool s ) {
  if( s ) PORTB |= B000100;    // output 10 to HIGH
  else    PORTB &= B111011;    // output 10 to LOW
}

//
// SecondSynchro() = gives second syncho for debugging
//____________________________________________________________________________________________

void SecondSynchro( bool s ) {
  if( s ) PORTB |= B000001;    // output 8 to HIGH
  else    PORTB &= B111110;    // output 8 to LOW
}

//
// MilliSynchro() = gives synchro every 20ms
//____________________________________________________________________________________________

void MilliSynchro( bool s ) {
  if( s ) PORTB |= B000010;    // output 9 to HIGH
  else    PORTB &= B111101;    // output 9 to LOW
}

//
// BlinkingLed() = function to drive blinking led
//____________________________________________________________________________________________

void BlinkingLed( bool s, bool c ) {
  if( !s ) {
    PORTB &= B011111;      // output 13 to LOW
    PORTB &= B101111;      // output 12 to LOW
  }
  else {
    if( c ) {
      PORTB |= B100000;    // output 13 to HIGH
      PORTB &= B101111;    // output 12 to LOW
    }
    else {
      PORTB |= B010000;    // output 12 to HIGH
      PORTB &= B011111;    // output 13 to LOW
    }
  } 
}

Credits

philippedc

8 projects • 74 followers

ALS162 an alternative to DCF77 time radio with Arduino Uno

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Custom parts and enclosures

ALS162 time radio receiver manual

ALS162 time radio receiver manual

Schematics

ALS162-time radio receiver diagram

Code

horloge_ALS162-v0.9.ino

Credits

philippedc

Comments

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ALS162 an alternative to DCF77 time radio with Arduino Uno

ALS162 an alternative to DCF77 time radio with Arduino Uno

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Custom parts and enclosures

ALS162 time radio receiver manual

ALS162 time radio receiver manual

Schematics

ALS162-time radio receiver diagram

Code

horloge_ALS162-v0.9.ino

Credits

philippedc

Comments

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