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DCF77 Radio Time Signal

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  • • #1

    Hi,

    Thought you might find this interesting. I'll try and post it into a module/tutorial soon, but this code decodes the time signal from the DCF77 time transmissions which cover europe on 77.5kHz.

    Someone's selling receivers on eBay here or you can almost certainly rip one out of an old radio clock.

    var minuteData = "";
var lastData = getTime();

// Decode 4 bits into a number
function decode4(s) {
  return (0|s[0])*1 + (0|s[1])*2 + (0|s[2])*4 + (0|s[3])*8;
} 

// xor all items in s and return the result (for parity checks)
function xor(s) {
  var r = 0;
  for (var i=0;i<s.length;i++) r^=s[i];
  return r;
}

// decode the DCF77 time transmission
function decodeMinute(d) {
  console.log(d, d.length);
  
  if (xor(d.substr(21,7))!=d[28]) { 
    console.log("Bad minutes");
    return;
  }
  var minute = decode4(d.substr(21,4)) + decode4(d.substr(25,3))*10;
  if (xor(d.substr(29,6))!=d[35]) { 
    console.log("Bad hours");
    return;
  }
  var hour = decode4(d.substr(29,4)) + decode4(d.substr(33,2))*10;
  if (xor(d.substr(36,22))!=d[58]) { 
    console.log("Bad date");
    return;
  }
  var day = decode4(d.substr(36,4)) + decode4(d.substr(40,2))*10;
  var doy = decode4(d.substr(42,3));
  var month = decode4(d.substr(45,4)) + decode4(d.substr(49,1))*10;
  var year = decode4(d.substr(50,4)) + decode4(d.substr(54,4))*10;
  console.log(hour+":"+minute+", "+day+"/"+month+"/"+year);
  
  var date = new Date(2000+year, month-1, day, hour, minute, 0, 0);
  console.log(date.toString());
}

function onSec(e) {  
  // Work out what bit we got
  var d = e.time-e.lastTime;
  var bit = (d<0.15)?0:1;
  // if we had a 2 sec gap then it's the beginning of a minute
  if (e.time-lastData > 1.5) {
    decodeMinute(minuteData);
    minuteData = "";
  }
  lastData = e.time;  
  // now add this bit of data
  minuteData += bit;
}

setWatch(onSec, dataPin, { edge:"falling", repeat:true, debounce:75 });
  • • #2

    Hi Gordon,

    i use the receiver from Conrad. It is a little bit different from the one on Pollin.

    i tried your sample code:

    require("DCF77").connect(B5, function(err, date, info) {
  if (err)
    console.log("Invalid time received: " + err);
  else
    console.log(date.toString(), info);
});

    But i haven't got any valid results. So i tried the dcf77 library from (http://thijs.elenbaas.net/2012/04/arduino-dcf77-radio-clock-receiver-library/)
    with an arduino one.

    At the beginning i didn't get valid result there either, but then i tested his debug code.
    i saw that his pulsewitdh differed from mine.

    he had 130 and 230ms.
    on my side the pulses where 80 and 180ms:

    Cycle: 904 Pulse :185
Cycle: 999 Pulse :88
Cycle: 1002 Pulse :84
Cycle: 992 Pulse :191
Cycle: 1008 Pulse :87
Cycle: 1007 Pulse :178

    After i changed the DCFSplitTime from 180 to 120 in his dcf77.h...

    _#define DCFSplitTime 120

    ... i got a vaild time.

    Waiting for DCF77 time ... 
It will take at least 2 minutes until a first update can be processed.
0:00:01 1 1 1970
0:00:02 1 1 1970
0:00:03 1 1 1970
0:00:04 1 1 1970
0:00:05 1 1 1970
0:00:06 1 1 1970
...
0:02:09 1 1 1970
0:02:10 1 1 1970
0:02:11 1 1 1970
0:02:12 1 1 1970
0:02:13 1 1 1970
Time is updated
22:26:01 15 11 2015
22:26:02 15 11 2015
22:26:03 15 11 2015
22:26:04 15 11 2015
22:26:05 15 11 2015
...
22:26:58 15 11 2015
22:26:59 15 11 2015
22:27:00 15 11 2015
Time is updated
22:27:01 15 11 2015
22:27:02 15 11 2015
22:27:03 15 11 2015
...

    How can i achieve this with the espruino?

    PS: i also used a 10k resistor to pull up the Data Pin.

  • • #3

    i guess the problem could be the setWatch function.
    i'm using the wifi adapter and an i2c oled display on the same espruino.

    so i tried a emtpy one with only the DCF77 sample.
    but i still don't get a valid time:

     _____                 _
|   __|___ ___ ___ _ _|_|___ ___
|   __|_ -| . |  _| | | |   | . |
|_____|___|  _|_| |___|_|_|_|___|
          |_| http://espruino.com
 1v80 Copyright 2015 G.Williams
>echo(0);
=undefined
Erasing Flash.....
Writing..........
Compressed 81600 bytes to 7529
Checking...
Done!
10
20
30
40
50
60
Invalid time received: Bad date
70
80
90
100
110
120
Invalid time received: Bad minutes
130
140
150
160
170
180
190
200
210
220
230
Invalid time received: Bad minutes
240
250
260
270
280
290
Invalid time received: Bad date
300
310
320
330
340
Invalid time received: Bad minutes
350
360
370
380
390
400
Fri Apr 25 2036 21:13:00 GMT+0000 { "CEST": true, "CET": true }
  • • #4

    i updated the firmware and switched to pin B6.

    now i get a valid time :)

     _____                 _
|   __|___ ___ ___ _ _|_|___ ___
|   __|_ -| . |  _| | | |   | . |
|_____|___|  _|_| |___|_|_|_|___|
          |_| http://espruino.com
 1v81 Copyright 2015 G.Williams
>echo(0);
=undefined
Erasing Flash.....
Writing.......
Compressed 81600 bytes to 4745
Checking...
Done!
pulsewidth: 0.16911602020
Invalid time received: Bad minutes
pulsewidth: 0.09433269500
pulsewidth: 0.09107685089
pulsewidth: 0.08496856689
pulsewidth: 0.08354568481
pulsewidth: 0.08212578296
pulsewidth: 0.09331417083
pulsewidth: 0.17105960845
pulsewidth: 0.17469120025
pulsewidth: 0.07842826843
pulsewidth: 0.17037200927
pulsewidth: 0.07430648803
pulsewidth: 0.17654514312
pulsewidth: 0.07944297790
pulsewidth: 0.08435630798
pulsewidth: 0.17442226409
pulsewidth: 0.08007431030
pulsewidth: 0.08116531372
pulsewidth: 0.08446788787
pulsewidth: 0.17115879058
pulsewidth: 0.17611885070
pulsewidth: 0.07796955108
pulsewidth: 0.17144978046
pulsewidth: 0.08308219909
pulsewidth: 0.17642116546
pulsewidth: 0.08210074901
pulsewidth: 0.08147811889
pulsewidth: 0.08908569812
pulsewidth: 0.17521846294
pulsewidth: 0.08436203002
Invalid time received: Bad minutes
pulsewidth: 0.08617496490
pulsewidth: 0.17422580718
pulsewidth: 0.17254734039
pulsewidth: 0.08129310607
pulsewidth: 0.08000469207
pulsewidth: 0.07793712615
pulsewidth: 0.08469009399
pulsewidth: 0.17134666442
pulsewidth: 0.07955360412
pulsewidth: 0.08358573913
pulsewidth: 0.17171764373
pulsewidth: 0.16930770874
pulsewidth: 0.16940021514
pulsewidth: 0.17125415802
pulsewidth: 0.07798385620
pulsewidth: 0.07773876190
pulsewidth: 0.08058834075
pulsewidth: 0.16745769977
pulsewidth: 0.08179664611
pulsewidth: 0.17019271850
pulsewidth: 0.08226764202
pulsewidth: 0.16649723052
pulsewidth: 0.07572460174
pulsewidth: 0.07742798328
pulsewidth: 0.17198657989
pulsewidth: 0.07287502288
pulsewidth: 0.08357334136
pulsewidth: 0.08595657348
pulsewidth: 0.07994079589
pulsewidth: 0.07726287841
pulsewidth: 0.08137893676
pulsewidth: 0.08567523956
pulsewidth: 0.08365154266
pulsewidth: 0.08036613464
pulsewidth: 0.07942295074
pulsewidth: 0.08462131023
pulsewidth: 0.17574119567
pulsewidth: 0.17203903198
pulsewidth: 0.06586933135
pulsewidth: 0.17288875579
pulsewidth: 0.08118247985
pulsewidth: 0.17242527008
pulsewidth: 0.07482910156
pulsewidth: 0.08241367340
pulsewidth: 0.17064762115
pulsewidth: 0.07899856567
pulsewidth: 0.08000206947
pulsewidth: 0.08048152923
pulsewidth: 0.17255878448
pulsewidth: 0.17012310028
pulsewidth: 0.07951927185
pulsewidth: 0.17014408111
pulsewidth: 0.08236026763
pulsewidth: 0.16853904724
pulsewidth: 0.08116734027
pulsewidth: 0.08185195922
pulsewidth: 0.08379852771
pulsewidth: 0.17349720001
pulsewidth: 0.08322811126
Mon Nov 16 2015 00:12:00 GMT+0000 { "CEST": true, "CET": true }
  • • #5

    Ahh, great! Glad you got it sorted!

    I guess it could have been a firmware issue then? I'm surprised if the pin that was used made any difference.

  • • #6

    Hi,

    i'm, sorry but that was only one lucky shot. i didn't get a valid time after that try.
    the pulswidth varies very much. sometimes its about 600ms long. some times the pulses a triggert much faster than one per second.

    i will try to record that tonight.

  • • #7

    That seems very strange... The Pico's RTC can sometimes be as much as 10% out because it's using the internal oscillator (that will be fixed soon hopefully), but it shouldn't be out by any more than that.

    Maybe you could connect an LED across the signal wire from the radio so you can see what it's really doing?

    It's possible that it's just receiving a lot of noise alongside the signal. The signal itself is very weak. To get to reliable I had to put mine right near the window.

  • • #8

    i live less then 100km away from frankfurt. i will try again without the wireless shield and the oled display.

  • • #9

    I suppose it's possible that the wireless (ESP8266?) is causing quite a lot of noise on the power supply lines, and that could be upsetting your receiver?

  • • #10

    I tried a 10µF capacitor between + and - of the DCF77 shield. But didn't see any difference.

  • • #11

    not working:
    https://youtu.be/LK4eFga2P7E

    working:

    I think i will buy a new DCF receiver. i can get it to work but its not stable. not on the arduino nor on the espruino.

    Code:

    function wlan() {

  digitalWrite(B9,1); // enable on Pico Shim V2
  Serial2.setup(115200, { rx: A3, tx : A2 });
  var wifi = require("ESP8266WiFi_0v25").connect(Serial2, function(err) {
    if (err) throw err;

    wifi.reset(function(err) {
      if (err) throw err;
      console.log("Connecting to WiFi");
      wifi.getAPs(function(err, aps) {
        console.log("Scanning Aps");
        //console.log(aps);
      });

      wifi.connect("XXX","XXX", function(err) {
        if (err){
          return console.log("NO Wifi");
        }

        var myip;

        wifi.getIP(function(err, ip) {
          myip = ip;
          console.log("Connected to:",myip);
          //printscreen(myip,13);
        });


        var http = require("http");
        http.createServer(function (req, res) {

            var a = url.parse(req.url, true);

            text1 = (a.query && a.query.t1 || "");
            text2 = (a.query && a.query.t2 || "");
            
            if (a.query && (a.query.t1 || a.query.t2)){
              printscreen(text1,10);
              setTimeout(function(){printscreen(myip,13);},2500);
            }

            res.writeHead(200, {'Content-Type': 'text/html'});
            res.write('<html><head><meta name="viewport" content="width=320"/></head><body>');
            res.write('LCD Display:<input id="t1" value="'+text1+'" type="text"><br>');
            res.write('LCD Display:<input id="t2" value="'+text2+'"type="text"><br>');
            res.write('<input type="button" onclick="get()" value="senden"><br>');
            res.write('<script> function get(){var e;window.XMLHttpRequest&&(e=new XMLHttpRequest),e.onreadystatechange=function(){4==e.readyState&&200==e.status&&console.log("done")};var t=document.getElementById("t1").value,n=document.getElementById("t2").value;e.open("GET","lcd/?t1="+t+"&t2="+n,!0),e.send()} </script>');
            res.end('</body></html>');

        }).listen(80);


      });
    });
  });

}


function onInit(){
  console.log("start");
  wlan();
  oled();
}


var img2 = {
  width : 32, height : 32, bpp : 1,
  transparent : 0,
  buffer : E.toArrayBuffer(atob("AAAAAAAAeAAAf/4AH/+bAH/ABQBoAAeAaAADwHQAAf5aAfCfS/8/sUXP//1G//AdQ/wAHUAAAB1AAAAdQAAAHWAAABNgAAAeYAAAEOAAABDgAAAQ8AAAGPgAABz4AAAcfAAAnD4AP/A+B//AHz//wA///4AAP+AAABgAAAAAAAA="))
};

function image(){
  //g.clear();
  g.drawImage(img2, 96, 0);
  //g.flip();
}



var g;
function printscreen(line1,line2,size){

  if (init !== 0){
    clearTimeout(init);
    init=0;
  }
  g.clear();
  // write some text
  g.setFontVector(size);
  g.drawString(line1,2,2);
  g.drawString(line2,2,20);
  // write to the screen
  g.flip();

}

var init=0;
var step=1;
function clear(){

  var p;
  var p1=".  ";
  var p2=" . ";
  var p3="  .";
 
  if (step==1){
    p=p1;
  }
  if (step==2){
    p=p2;
  }
  if (step==3){
    p=p3;
  }
  step++;
  if (step == 4) step=1;
  
  g.clear();
  g.setFontVector(14);
  g.drawString("waiting "+p,2,4);
  
  image();
  g.flip();
  
  init=setTimeout(clear,300);
  
}

function oled(){

  digitalWrite(B4, LOW);
  digitalWrite(B4, HIGH);
  I2C2.setup({scl:B10, sda:B3});
  g = require("SSD1306").connect(I2C2, clear,{ height : 32 });

}


function DCF77(){

  // Decode 4 bits into a number
  function decode4(s) {
    return (0|s[0])*1 + (0|s[1])*2 + (0|s[2])*4 + (0|s[3])*8;
  }

  // xor all items in s and return the result (for parity checks)
  function xor(s) {
    var r = 0;
    for (var i=0;i<s.length;i++) r^=s[i];
    return r;
  }

  // decode the DCF77 time transmission
  function decode(d, callback) {
    if (xor(d.substr(21,7))!=d[28])
      return callback("Bad minutes");

    var minute = decode4(d.substr(21,4)) + decode4(d.substr(25,3))*10;
    if (xor(d.substr(29,6))!=d[35]) 
      return callback("Bad hours");

    var hour = decode4(d.substr(29,4)) + decode4(d.substr(33,2))*10;
    if (xor(d.substr(36,22))!=d[58]) 
      return callback("Bad date");

    var day = decode4(d.substr(36,4)) + decode4(d.substr(40,2))*10;
    var doy = decode4(d.substr(42,3));
    var month = decode4(d.substr(45,4)) + decode4(d.substr(49,1))*10;
    var year = decode4(d.substr(50,4)) + decode4(d.substr(54,4))*10;
    //console.log(hour+":"+minute+", "+day+"/"+month+"/"+year);

    var date = new Date(2000+year, month-1, day, hour, minute, 0, 0);
    return callback(null, date, { CEST:!!d[17], CET:!!d[18] } );
  }


  this.connect = function(dataPin, callback) {
    var dcf = {
      last : getTime(),
      bits : ""
    };

    setWatch(function (e) {  
      // Work out what bit we got
      var d = e.time-e.lastTime;
      console.log("pulsewidth:",(d*1000).toString().substring(0, 3));
      var bit = (d<0.12)?0:1;
      // if we had a 2 sec gap then it's the beginning of a minute
      if (e.time - dcf.last > 1.5) {
        decode(dcf.bits, callback);
        dcf.bits = "";
      }
      dcf.last = e.time;  
      // now add this bit of data
      dcf.bits += bit;
      if (dcf.bits.length>59)
        dcf.bits = dcf.bits.substr(-59);
    }, dataPin, { edge:"falling", repeat:true, debounce:60 });

    return dcf;
  };
}



var Clock = require("clock").Clock;
var clk=new Clock(0);


  
var dcf = new DCF77();
dcf.connect(B6, function(err, date, info) {
  if (err){
    console.log("Invalid time received: " + err);
  }else{
    console.log(date.toString(), info);
    clk.setClock(date.getTime());
  }

});


var woche = ["So","Mo","Di","Mi","Do","Fr","Sa"];

setInterval(function(){
  
  var date = clk.getDate();
  
  var weekday = date.getDay(); //0-31
  var wochentag = woche[weekday];
  
  var jahr = date.getFullYear();
  var monat = date.getMonth()+1; monat=(monat<10)?"0"+monat:monat;
  var tag = date.getDate();        tag=(tag<10)?"0"+tag:tag;
  
  var stunden = date.getHours(); stunden=(stunden<10)?"0"+stunden:stunden;
  var minute = date.getMinutes();minute=(minute<10)?"0"+minute:minute;
  var sek = date.getSeconds();   sek=(sek<10)?"0"+sek:sek;
  
  
  var s1 = wochentag+". "+tag+"."+monat+"."+jahr;
  var s2 = stunden+":"+minute+":"+sek;
  
  printscreen(s1,s2,10);
  
},1000);



save();

    @Gordon thank you for help.

  • • #12

    No problem - sorry you didn't have any luck with it.

    Radio stuff is tricky. It's always hard to know if it's software, the hardware, or just interference that's at fault :)

  • • #13

    Hello Gordon,
    I know it is an old entry, but I could not find any other entry regarding DCF77.
    I try to continuously rund the DCF77 module, but only get the attached result. After it runs for a minute or so it comes back with the attached message 'running out of memory'.
    I am using the Conrad module with it, tried different ports and the normal as well as the inverted output.
    Do you possibly have a hint what I do wrong there?
    I am completely new with JavaScript though.
    Joe

    1 Attachment

    • DCF77.jpg
  • • #14

    problem is the module starts a watch by itself, so your setInterval starts a watch every 2s, which might lead to the memory problem

    but you can create a custom module locally (put it into modules folder and call it myDCF77 or something)

    and use it this way

    setInterval(function(){
    var watchId;
    var result = require('myDCF77').connect(B1, function(err, date, info) {
      if (err) {
        console.log("Invalid time received: " + err);
      }
      else {
        console.log('Date from DCF77 ' + date.toString());
        if(watchId) {
          clearWatch(watchId);
          watchId = undefined;
        }
      }
    });
    watchId = result.watchId;
  }, 1200000);

    ... the above needs a change inside the module as

    exports.connect = function(dataPin, callback) {
  var dcf = {
    last : getTime(),
    bits : '',
    watchId: undefined
  };
  dcf.watchId = setWatch(function (e) {
    // Work out what bit we got
    var d = e.time-e.lastTime;
    var bit = (d<0.15)?0:1;
    // if we had a 2 sec gap then it's the beginning of a minute
    if (e.time - dcf.last > 1.5) {
      decode(dcf.bits, callback);
      dcf.bits = "";
    }
    dcf.last = e.time;
    // now add this bit of data
    dcf.bits += bit;
    if (dcf.bits.length>59)
      dcf.bits = dcf.bits.substr(-59);
  }, dataPin, { edge:"falling", repeat:true, debounce:75 });
  return dcf;
};

    keep all other functions as is

  • • #15

    err if you dont mind the power use you can use the module as is, just use it without setInterval

  • • #16

    That interval was exactly the problem. The language is quite different from like Pascal or even Assembler. I see I have to think completely different with JavaScript and its syntax.
    Thank you very much for your quick profound help.
    Joe

  • • #17

    if you are interested in some background

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DCF77 Radio Time Signal

Posted by Avatar for Gordon @Gordon

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