Updated Display Options for 2011


Example with 100mm antenna courtesy of Steve Pocock KC0NGU

"Receives U.S. Govt WWVB digital radio time standard broadcast from Ft Collins, CO"

My own using a Olimex PCB and a high end Spark Fun case :)

PIC 16F628A and CMMR-6 module
LCD display of local WWVB time and date
This project combines the venerable PIC 16F628A micro, CMMR-6 60 KHz WWVB time receiver and a LCD display to make a very accurate clock.
The program was written in Microchip assembly language and is open source for non commercial use.
- Support for a 16x1 or 16x2 LCD with graphic signal quality and lock indication.
- 9600 baud serial output on command on the 16x2 version with optional circuitry.

The WWVB module is available at DigiKey, complete with a loopstick antenna for about $11.

The photos provided by Steve Pocock KC0NGU showcase his clean build of this design.
The CMMR-6 module is center right with the attached loop stick antenna mounted below.
This revision adds time zone configuration for +/-12 hours from GMT, and displays this offset.
Added a valid bit indication that updates every second when good data is received.
The new 16x2 display firmware supports the optional RS232 circuitry to communicate serially at 9k6 baud.

Theory of Operation
Schematic (click for PDF)
The signal is a low frequency (60 KHz) AM, 1 baud digital transmission broadcast from Ft Collins, CO.
The carrier is modulated at two distinct amplitudes, one 10db lower in power. The high and low level pulse width ratios correspond to one of three bits: zero (0), one (1) and a frame marker.  Each new 60 bit packet begins with two consecutive frame marker bits.  This sequence only occurs at the beginning of the packet and is used as a synchronizer.  Afterwards, a frame marker occurs every 10 seconds for the next 50 seconds before the sequence repeats.
Once synchronized, the program compares the incoming data to a valid structure pattern.  If any of the frame markers are missing or out of sequence, the whole packet is rejected.
Next, the non data bits are stripped to form six bytes, each 8 bits wide, which contain all of the data to be extracted. Then the recovered data is stored in named variables that can be read and displayed to the LCD.
For more information about low frequency radio - Wiki Low Freq

New Features:

Worldwide time zone adjust for displaying local time
Graphic indication of bit reception
PCB created by NI2O for this project on OSH Park
Separate schematic for NI2O pcb included in file download.

FILE PACK (ZIPPED) contains firmware, schematic and instructions.

Experimenters Zone:

Advanced software for the WWVB decoder/clock
Analyze and log low frequency propogation
Signal Reporter - tallys good/bad data
Internal clock auto calibrate
Uses 16x2 line LCD display

More info: Ask Mike

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This page was updated 10-11-2014