AD9850 DDS as a RF generator

[RoLorenzoni]

Hi!
I am new with programming, but I found your project really interesting.
I live in a country that does not have the time signal available, so I have no other choice but constructing a transmitter.
I tried your "minimal" project but it wasn't able to set my citizen watches. The Rx indicator shows some signal reception but it always fails.
Then I got a AD9850 DDS RF generator and it's really easy to create a sine 60khz carrier.
Changing a WWVB sample code from vinmarshall (https://github.com/vinmarshall/WWVB-Clock), I could generate a WWVB signal that was correctly received by the watches.
Now, I'm trying to combine the ad9850 code with your wwvb library, but with no sucess.
I would be very happy if you could help me with that, because I am new to programming.
I am using an arduino nano, a ublox 6 GPS module to get acurate time and the AD9850 to broadcast it.
Thanks in advance.

here is the code I used to generate the carrier.

/* WWVB Test Signal v 1.0
*

• This code uses an Arduino to simulate the C-Max CMMR-6P TCO positive
• output signal. This was written for debugging WWVB Clock
• Receiver code.
• This code is adapted from the WWVB Receiver Simulator provided by
• Capt.Tagon at duinolab.blogspot.com. It expands on that code by
• incrementing the time and date starting from that set in the
• setup() routine. This also contains debugging code to display
• this value on the Serial monitor.
• This code supports the "Atomic Clock" article in the April 2010 issue
• of Popular Science. There is also a schematic for this project. There
• is also WWVB signal simulator code, to facilitate debugging and
• hacking on this project when the reception of the WWVB signal
• itself is less than stellar.
• The code for both the clock and the WWVB simulator, and the schematic
• are available online at:
• http://www.popsci.com/diy/article/2010-03/build-clock-uses-atomic-timekeeping
• and on GitHub at: http://github.com/vinmarshall/WWVB-Clock
• Copyright (c) 2010 Vin Marshall (vlm@2552.com, www.2552.com)
• Permission is hereby granted, free of charge, to any person
• obtaining a copy of this software and associated documentation
• files (the "Software"), to deal in the Software without
• restriction, including without limitation the rights to use,
• copy, modify, merge, publish, distribute, sublicense, and/or sell
• copies of the Software, and to permit persons to whom the
• Software is furnished to do so, subject to the following
• conditions:
• The above copyright notice and this permission notice shall be
• included in all copies or substantial portions of the Software.
• THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
• EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
• OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
• NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
• HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
• WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
• FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
• OTHER DEALINGS IN THE SOFTWARE.

*/

#include <AD9850.h>

const int W_CLK_PIN = 7;
const int FQ_UD_PIN = 8;
const int DATA_PIN = 10;
const int RESET_PIN = 11;

double freq = 60000;
double trimFreq = 124999500;

int phase = 0;

/* WWVB time format struct - acts as an overlay on wwvbRxBuffer to extract time/date data.

• All this points to a 64 bit buffer wwvbRxBuffer that the bits get read from as the
• sample data stream is transmitted. (Thanks to Capt.Tagon @ duinolab.blogspot.com)

*/

struct wwvbBuffer {
unsigned long long U12 :4; // no value, empty four bits only 60 of 64 bits used
unsigned long long Frame :1; // framing
unsigned long long Dst :2; // dst flags
unsigned long long Leapsec :1; // leapsecond
unsigned long long Leapyear :1; // leapyear
unsigned long long U11 :1; // no value
unsigned long long YearOne :4; // year (5 -> 2005)
unsigned long long U10 :1; // no value
unsigned long long YearTen :4; // year (5 -> 2050)
unsigned long long U09 :1; // no value
unsigned long long OffVal :4; // offset value
unsigned long long U08 :1; // no value
unsigned long long OffSign :3; // offset sign
unsigned long long U07 :2; // no value
unsigned long long DayOne :4; // day ones
unsigned long long U06 :1; // no value
unsigned long long DayTen :4; // day tens
unsigned long long U05 :1; // no value
unsigned long long DayHun :2; // day hundreds
unsigned long long U04 :3; // no value
unsigned long long HourOne :4; // hours ones
unsigned long long U03 :1; // no value
unsigned long long HourTen :2; // hours tens
unsigned long long U02 :3; // no value
unsigned long long MinOne :4; // minutes ones
unsigned long long U01 :1; // no value
unsigned long long MinTen :3; // minutes tens
unsigned long long U00 :1;
};

// We point the struct and the unsigned long long at the
// same memory space so we can access the bits using
// both paradigms.
struct wwvbBuffer * buffer = (struct wwvbBuffer *) malloc(sizeof(struct wwvbBuffer));
unsigned long long * timeBits = (unsigned long long *) buffer;

/*

• setup
• uC Initialization
  */

void setup() {

// Setup the Serial port out and the WWVB signal output pin

DDS.begin(W_CLK_PIN, FQ_UD_PIN, DATA_PIN, RESET_PIN);
DDS.calibrate(trimFreq);

    // Preset the time struct 
    *timeBits = 0x0000000000000000;
    buffer->MinTen = 5;
    buffer->MinOne = 7; 
    buffer->HourTen = 2;
    buffer->HourOne = 3;
    buffer->DayHun = 3;
    buffer->DayTen = 6;
    buffer->DayOne = 5;
    buffer->OffSign = 5;  // 2 -> -  5 -> +
    buffer->OffVal = 3;
    buffer->YearTen = 1;
    buffer->YearOne = 0;
    buffer->Dst = 3; // 0 no dst, 1 dst ending, 2 dst starting, 3 dst
    buffer->Leapyear = 0;
    buffer->Leapsec = 0;

}

/*

• loop
• Main program loop
  */

void loop() {

// Print the Date & Time to the Serial port for debugging.
int year = (buffer->YearTen * 10) + buffer->YearOne;
int day = (buffer->DayHun * 100) + (buffer->DayTen * 10) + buffer->DayOne;
int hour = (buffer->HourTen * 10) + buffer->HourOne;
int minute = (buffer->MinTen * 10) + buffer->MinOne;
char date[30];
sprintf(date, "%.2i:%.2i %.3i, 20%.2i\n", hour, minute, day, year);
Serial.print(date);

// Step through each bit in this frame
int position = 0;
for (int i = 63; i >= 4; i--) {
// Mask off all bits but the one in question.
// This singles out one bit, moving from MSB to LSB
unsigned long long mask = (unsigned long long) 1 << i;
unsigned long long masked = (*timeBits) & mask;

// Determine if there was a 1 in that bit position
int bit = ((*timeBits) & mask)?1:0;

            // Determine if we're at a Marker position
            int mark = 0;
            if ( (position == 0) || 
                 ((position + 1) % 10 == 0) ) {
                   mark = 1;
            }
            position++;

// Rattle off each bit

// Debug output to the Serial port
// Print in groups of 4. Makes cross ref to hex easier
if ( (i+1) % 4 == 0) {
  Serial.println("");
} 

            if (mark) { 
              Serial.print("M"); 
              sendMark();
            } else if (bit == 0) {
              Serial.print("0");
              sendUnweighted();
            } else if (bit == 1) {
              Serial.print("1");
              sendWeighted();
            }

}
Serial.println("");

// Increment the Time and Date
if (++(buffer->MinOne) == 10) {
buffer->MinOne = 0;
buffer->MinTen++;
}

if (buffer->MinTen == 6) {
buffer->MinTen = 0;
buffer->HourOne++;
}

    if (buffer->HourOne == 10) {
            buffer->HourOne = 0;
            buffer->HourTen++;
    }

    if ( (buffer->HourTen == 2) && (buffer->HourOne == 4) ) {
            buffer->HourTen = 0;
            buffer->HourOne = 0;
            buffer->DayOne++;
    }
    
    if (buffer->DayOne == 10) {
            buffer->DayOne = 0;
            buffer->DayTen++;
    }
    
    if (buffer->DayTen == 10) {
            buffer->DayTen = 0;
            buffer->DayHun++;
    }
    
    if ( (buffer->DayHun == 3) && 
         (buffer->DayTen == 6) &&
         (buffer->DayOne == (6 + (int) buffer->Leapyear)) ) {
             // Happy New Year.
             buffer->DayHun = 0;
             buffer->DayTen = 0;
             buffer->DayOne = 1;
             buffer->YearOne++;
     }
     
     if (buffer->YearOne == 10) {
       buffer->YearOne = 0;
       buffer->YearTen++;
     }
     
     if (buffer->YearTen == 10) {
       buffer->YearTen = 0;
     }

}

/*

• sendMark
• Output a Frame / Position marker bit
  */

void sendMark() {

// Send low for 0.8 sec
DDS.down();
delay(799);

// Send high for 0.2 sec
DDS.setfreq(freq, phase);
delay(199);

return;
}

/*

• sendWeighted
• Output a Weighted bit (1)
  */

void sendWeighted() {

// Send low for 0.5 sec
DDS.down();
delay(499);

// Send high for 0.5 sec
DDS.setfreq(freq, phase);
delay(499);

return;
}

/*

• sendUnweighted
• Output an Unweighted bit (0)
  */

void sendUnweighted() {

// Send low for 0.2 sec
DDS.down();
delay(199);

// Send high for 0.8 sec
DDS.setfreq(freq, phase);
delay(799);

return;
}

[micooke]

Yeah im Australian, no wwvb here either!

Thanks for pointing me to that library, its actually a similar approach to what my new wwvb_jjy library is taking - but i use a union to access the bits as a buffer, jjy or wwvb. Interesting that it syncs on your watch, i will have to test it out against my clock (BALDR brand, same as @mr-sneezy) which arrived yesterday.

Also, i ordered that exact dds board a week ago so should be able to use the same test setup (when it eventually arrives). My library has worked with desk clocks, but not watches - i had been wondering if this is because the arduino outputs a 0 to 5v square wave instead of a -5 to 5v sine, looks like it may.

Ill have a look at that library and get back to you. In the meantime, if you wanted to test against an early release have a look at the tx example in my wwvb_jjy library. It requires my pwm library. Initialise the dds in setup, turn it off in the overflow isr and turn it on in the compare isr.

Cheers

[micooke]

Okay im dumb. Those updates failed, i should be able to fix it easily enough though. I tested last night and got my new library syncing my desk clock but haven't updated the changes yet - needs a tidy up of debug code.

Ive reopened this until the new library is tested and working, then ill transition to that.

Cheers

[RoLorenzoni]

Hello.
As I'm not a good programmer, I'm testing the range of the signal from the ad9850.
I connected an AM loop antenna on the analog1 output pin of the DDS.
Even without a proper modulation, I could make a simple program that switches the 60khs carrier on and off in a regular half second interval.
Of course, the watch doesn't sync, but, it listens to the signal and shows "strong" signal even 3 meters away from the antenna.
An electronic technician told me that it's easy to extend the range even more by using a MOSFET transistor to amplify the signal.
My idea is that one transmitter could have the range all over the house.
cheers

[RoLorenzoni]

Oh, forgot to say...
Differently from de PWM output at arduino board, you should connect the other end of the antenna to the gnd pin in order to have a good transmission.

[micooke]

Regarding the transmitter, you will need to check the applicable regulations on your country regarding transmit power. The example i use is current limited by grounding the antenna through a led - this is more to protect the arduino pin, although they are internally limited to 20mA anyways.

Generally you will be limited to 100mW ERP, which is Pt(av) × Gt. The max theoretical duty cycle is 73% over a 60s frame (7 markers at 20%, 53 low at 80%). Pt(av) = 5V × 20mA ×73% = 0.073W = 73mW. To keep under 100mW the max antenna gain would be 10×log10(100/73) = 1.36dB.

If you are not limited to 100mW you have a few options. You could use the arduino to switch in a higher voltage using a fet or op amp, or pull a higher current through a fet. The 2n2222 (800mA max) is a good common BJT which should work well, or a 2n7000 (200mA) if you wanted a mosfet (or BS170 - 500mA, a less common 2n7000 equivalent).

[baradhili]

remember the regs are always about ERP - effective radiated power.... at 60kHz - you will be more worried about planning regulations than transmitted power as the 1/4 length is huge....

Though careful matching is always a good idea to protect your transmitter driver..

[micooke]

You mean I can't install a 1.25km antenna out the back 😄

Actually I did forget how terrible the gain of these antennas are. They are classified as being electrically small, and i make no effort at impedance matching so probably 'worse than -10dB' if my memory serves me correctly.

So @RoLorenzoni - ignore my warning. Also, @mr-sneezy tells me its 10mW, not 100mW.

[baradhili]

it depends where you live :).... you might have enough space if you are in aust.. :)

…

On 2 May 2017 at 15:45, Mark Cooke ***@***.***> wrote: You mean I can't install a 1.25km antenna out the back 😄 Actually I did forget how terrible the gain of these antennas are. They are classified as being electrically small, and i make no effort at impedance matching so probably 'worse than -10dB' if my memory serves me correctly. So @RoLorenzoni <https://github.com/RoLorenzoni> - ignore my warning. Also, @mr-sneezy <https://github.com/mr-sneezy> tells me its 10mW, not 100mW. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#10 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAotFOySFPyJ8ZyOxWPjcSCcOS8NadrHks5r1t8wgaJpZM4NMDkd> .

[micooke]

Ill keep this open for a little bit - but the wwvb_jjy library is now working for a simple example so ill resolved this issue in that repo 🤞

[RoLorenzoni]

Oh thanks.
I'll test the wwvb_jjy today.
I found this app on the web.
http://www.jrcomputing.com.au/Set_Watch/Set_Watch_Manual.html
May be useful, specially for you, because it's JJY too.

[micooke]

Thanks for that, ill have to check it out.
Im closing this as i have an (untested) example in the new wwvb_jjy library - https://github.com/micooke/wwvb_jjy/blob/master/examples/AD9850_WWVB_tx/AD9850_WWVB_tx.ino

[micooke]

Hey @baradhili did you end up getting a board from Wingsy?

https://forum.allaboutcircuits.com/threads/i-built-it-now-can-i-sell-it.130898/page-2#post-1089916

I wound be interested in the schematic and what antenna you are using.

Cheers

[baradhili]

Not me sorry

…

On 31 May 2017 at 15:25, Mark Cooke ***@***.***> wrote: Hey @baradhili <https://github.com/baradhili> did you end up getting a board from Wingsy? https://forum.allaboutcircuits.com/threads/i-built-it-now-can-i-sell-it. 130898/page-2#post-1089916 I wound be interested in the schematic and what antenna you are using. Cheers — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#10 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAotFMOGETAQX6-0YbV0UD7fS7diLufXks5r_RXugaJpZM4NMDkd> .