time detection via WWVB and the CME8000 module

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I am attempting to provide automated time detection via the WWVB signal
for embedded logging devices. I want to be able to time/date stamp data
collection without requiring the user to set it manually. The CME8000
is a receiver chip that seems ideal. I have purchased and powered up
the CME8000-BUS-LP-01 module (easily available form Digi-Key). This
module uses one of the most bizarre protocols I have ever seen- a
mishmash of IIC, RS232, and others. The data sheet is also one of the
worst I've ever seen, requiring inference and extrapolation to figure
out how the thing actually works. The purpose of this long-winded post
is to ask if anyone else has used this device, and figured out how to
generate the CRC bytes required by the protocol. I have contacted C-MAX
(a chinese company), their domestic rep, and tech suport at DigiKey,
all to no avail. I have tried CRC16, CRCITT, (and their reverse
polynomials), msb-lsb and lsb-msb ordering of crc bytes without being
able to communicate to this opaque device. The pdf document
CME8000-BUS-B6.pdf) I downloaded from their site refers to sample
source code in the appendix- the appendix doesn't exist. If anyone has
cracked the CRC algorithm I would be very grateful for any help.

TIA
Harry Sieber
Sieber Consulting


Re: time detection via WWVB and the CME8000 module
Hi Harry,

Sorry I can't help with the CME8000, though I've tried using C-Max's
CMM6 without any luck. When I looked at what the CME8000 needed, I
figured that the software to decode the WWVB signal is not that big a
deal, so I went with the cheaper, smaller, simpler device.

However, as near as I can tell, I'm not getting any signal out of the
CMM6. I tried moving the antenna around, letting it run overnight,
using pull up and/or pull down resistors, but I get absolutely no
signal. C-Max's tech support confirmed I wired it up right (if you try
it, be careful: some wires go to the front of the board, and some go to
the back). Store-bought radio clocks work great when they're sitting
right next to the CMM6.

The one caveat in this is that I'm not a EE. I'm a software engineer
working with the CMM6 at home as a hobbyist. My tools are a voltmeter
and logic probe: no oscilloscope. And my knowledge of electronics is
weak. I might've screwed up something obvious, but I can't figure out
what.

If you choose to try the CMM6, please let me know what results you get.
I know my experience might discourage you from even attempting it, but
keep in mind that, if you can get it to work, it'll be cheaper and
smaller for your product, and the software really isn't that difficult.

Another choice is Galleon's EM2S WWVB receiver. It's like the CMM6, but
has been around much longer. However, I've had a hell of a time trying
to get them to answer their phone or return my voicemail or e-mail
messages. I sent them an order by US mail weeks ago, and I'm trying to
find out if they got it or not.

- Bob


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