C-MAX CMMR-6P-60 and ATMEGA324P

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Hi all,

I'm trying to get WWVB time from a C-MAX CMMR-6P-60 module with a ATMEGA324P.

The first problem I'm having is getting any kind of response out the CMMR module. All I've been getting is a constant output. Neither output is toggling. I've tried at night when the reception is supposed to be best. Has anyone tried using one of these modules with success?

Second, I'm trying to decide the best way to decode the WWVB time signal. The output is 1-baud. A low for 0.2 seconds is a binary zero, a low for 0.5 seconds is a binary one, a low for 0.8 seconds is a marker. I think the best way is to connect the output to one of the analog comparators and use a timer to time events. Should I just sample the signal every 50ms or should I use the timer to detect the edges? I'm afraid the signal will have many false transitions and the timer will get messed up. Any suggestions?

TIA.

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No one has suggestions?

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I would do pretty much as you propose. But, noise IS an issue. I guess that I would NOT use the receiver output as a direct capture input.

At 1 baud, you have PLENTY of time for digital filtering. So, I would sample at maybe 32X to 128X the baud rate. Then, I would use some sort of simple digital filter, such as an N-sample moving averager. The output of that will be "analog" (that is, a sequence of values) which can, then, be analyzed with a numeric threshold (ie, numeric comparator) such that the output of the comparator is NOW binary (sequence of 1's and 0's) which can be timed.

One of the things that might NOT be clear in all this is what I mean by "sample". That COULD be driven by a timer. Simply observe the receiver output with a port pin. Assign a numeric value to that sample if it happens to be high and a different number if it happens to be low. You COULD use an ADC channel, but I don't think that would buy much.

It a bit complex, but its a whole lot simpler in software than hardware, especially with the low pole frequencies needed for filters for those signals.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Thanks for your advice.

I'm having trouble getting any signal out of the WWVB module. I have two modules and neither seem to put out a signal. They're so simple so it's hard to imagine that I have it wired wrong. Oh well,.....

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Do you have the appropriate antenna connected to
your module ? How far away from the transmitter are you ?

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The module comes with an antenna attached. I'm in NJ which is far from the transmitter, but I have clocks that eventually pick it up.

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Is the PON input grounded? Try putting an LED on TCON. Also see http://www.prc68.com/I/Loop.shtml

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I just got my CMMR-6P-60 module from Digikey, connected it to Arduino and got no responce. I connected it to analog input so I could see ANYTHING. After that I just moved it away from PC as far as I could (my USB is about 4 feet) and turned my monitor off and got some 0s and 1s. So I am agree with ka7ehk, noise is an issue. Will try to move little bit further on next week.

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The antenna is also probably orientation sensitive. I think those things have a "loop-stick" antenna. This is a ferrite rod, typically 6" or more long. You need to orient this rod at right angles to the line between you and WWV (which is in Colorado). So the line is basically due west from NJ or SW from Wisconsin.

Did you get the antenna that should come with it? Is it properly connected? Is it NOT on a metallic surface? Is it oriented properly (as described, above)?

Also, check out the Circuit Cellar article on c-max.time that is linked on this page:

http://www.c-max-time.com/downlo...

Note, also, that the output is "analog". This MIGHT mean that you want to AC couple into the comparator input. Check the article for ideas about what works. ADC input might be used as a substitute for AC coupling, followed by some basic DSP. As previously mentioned, 1 bit per second gives you almost forever to do what ever processing you need. You could sample 10X per bit and still have forever.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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I am in Ann Arbor, Michigan. I start seeing reasonable data just after dusk. When the sun is setting in Fort Collins, assuming no electrical storms between me and WWVVB the data is pretty solid. Use pin 8 and the input capture facility of the atmega, works great. The antenna should be oriented parallel to the ground and perpendicular to the line from you to WWVB. Also I have been using 3 "D" cells for power and an LCD module for output and debugging. The data from my CMMR-6P-60 is much more reliable when the usb cable is disconnected from my laptop and the laptop is five or six feet away or asleep. If you want to work on this project during the day I have found at least two different WWVB transmitter projects on the net that you can use. Jim clearly knows what he is talking about with regard to WWVB reception and decoding issues, but it also appears that he has never purchased or worked directly with the CMMR-6P-60 evaluation module from Digi-Key or read the CME6005 data sheet. The only thing "analog" about the CMMR-6P-60 is the length of the output pulse. If you attach an LED and dropping resistor directly to the TCO or TCON pad you will see the bits and the intensity of the LED will never change.
Like I said I am using pin 8, the input capture of the atmega and then display the complement of the CMMR-6P-60 input on an output LED. If you would like to see my code so far or if you want to mostly do this yourself and just want some of my early experimental code to convince yourself that you are on the right track just send me a private message.