Install a CR1220 battery in the backup battery bail. This battery is optional, but if present will help the GPS receiver by preserving the satellite almanac across power cycling.

Insure a properly formatted and loaded µSD card is installed in the slot.

Adjust the trimpot near the board-mounted button to the center of its range. This trimpot adjusts the balance between the ticks/beeps and the sampled audio. Once you can hear the audio, adjust this pot for best balance.

Connect a GPS antenna to the SMA jack and plug a 2.1mm barrel connector with 5 VDC center positive to the power jack. The FIX LED (LED3) near the corner of the board and the GPS diagnostic light (LED1) should come on. As soon as the GPS receiver gets a fix, the FIX LED should start blinking at 1/2 Hz and the GPS diagnostic LED should go out. At some time a few seconds later, the clock should begin playing the audible timecode.

You can push the button any time (except during chiming) to turn the audible timecode on or off.

At any time, you can change the DIP switches to select the desired timezone. You can also turn switch 3 on or off to enable or disable the chimes. The chimes will only sound when the audible timecode is muted.

The default time zones available:

• 0 - UTC
• 1 - Pacific Time
• 2 - Mountain Standard Time (no DST - Arizona)
• 3 - Mountain Time
• 4 - Central Time
• 5 - Eastern Time
• 6 - Hawaii Standard Time (no DST)
• 7 - Alaska Time

If at any time LED2 lights, that indicates an error accessing the flash filesystem. The best suggestion is to recreate the filesystem image and reload it.

The board comes as a "quick kit" with the DIP switches unattached. If you're installing the clock in the laser-cut case, then install the DIP switches on the bottom of the board (opposite the components). Otherwise, it's up to you which side. If you prefer, you can connect some other switching mechanism up. The top 4 holes (nearest the center) are the switched pins. Shorting any of these to ground turns the switch "on."

For mounting in a case, you can connect a remote switch up to the 2 pin terminal near the on-board switch.

The speaker jack should be connected directly to a 4Ω or 8Ω speaker. The speaker terminals are a bridge output configuration - do not connect either one to ground. The bottom terminal is positive (but it doesn't really matter in practice).

For faster restarts after power outages, install a CR1220 battery under the battery bail on the board. This battery will likely last many years, as it is not used except when the board is unpowered (and even then the draw is very, very small).

Attach the speaker loosely to the front panel with 4 3/8" screws, lock washers and nuts. Once all 4 screws are loosely attached, tighten them using a figure X pattern.

Solder 4 wires to the speaker and button terminals. Use 22 gauge wire 6 inches long (to facilitate easier case assembly).

Attach the board to the back panel with 4 5/8" screws, 1/4" spacers, lock washers and nuts. Orient the board so that the DIP switches are visible through the cut-out with the switch numbers immediately above. The components should be facing upwards.

Attach the volume control to the back panel with its washer and nut. Use a 20 kΩ audio-taper pot.

Insert the button firmly through the hole in the top panel (the top panel doesn't have a front or back side).

Solder the speaker wires to the speaker terminals and the volume pot to the volume terminals. Make sure that the counter-clockwise end of the pot goes into the CCW hole on the board. The center is the wiper and the other terminal is the CW end.

Solder the two switch wires to the switch terminals, then bend those terminals down to about a 60 degree angle against the switch body.

Now is a good time to test the circuitry. Connect an antenna and apply power. Wait until the FIX LED (bottom left corner) begins to blink and the GPS LED (bottom of the two paired near the top middle of the board) goes out. Within a few seconds of that, the voice announcements should commence. Push the button to silence them and again to resume. Change the DIP switches to verify they function. Disconnect power and antenna for remaining assembly steps.

Insert 3/8" screw and loosely attach (2 turns max) a nut to all 8 holes in the front and back panels. Mate the top panel with the front and back panels. Tighten the four screws holding the top, front and back panels together.

Mate the bottom panel with the front, back and top panel assembly. Tighten the four screws holding the bottom panel in place.

Insert the remaining 4 3/8" screws through the two holes in the remaining holes in the top and bottom panels. As before, loosely attach nuts to each of the screws.

Install the right and left panels. Make sure that the antenna jack fits through the hole in the left side panel and the power jack is visible through the hole in the right side panel. Tighten the 6 screws holding each side panel in place.

Your assembly is now complete.

Replacing either the audio samples or editing the config file requires re-flashing the ROM chip.

Start by making disk image no larger than the flash chip (probably 4 MB). The image should have a standard MBR partition table and a single FAT-12, FAT-16 or FAT-32 partition on it. Copy all of the files into place (editing the config file to taste if desired). On Linux, the steps to do this:

• make a chip-sized file filled with 0xff (starting with all 1s is easier on the flash chip as it doesn't have to unnecessarily write unused space): dd if=/dev/zero bs=8192k count=1 | tr '\0' '\377' > image
• Make a FAT filesystem on it: mkfs.vfat image
• Mount it: sudo mount -o loop image /mnt
• Copy the files into it: cd /mnt && unzip $HOME/SD_audio.zip
• Unmount the image: sudo umount /mnt

Once you have the image file, you need to load it into the flash chip. First, jumper the !RESET of the controller low to keep it from interfering. The easy way to do this is to short pins 5 and 6 of the PDI programming port.

Next, connect an SPI flash programmer up to the flash programming port. The pinout of this port is the same as an AVR ISP port, with !CS replacing !RESET. Alternatively, you can use a clip over the flash chip itself (though that's a little more fiddly). One of the best ways to do this is use a Raspberry Pi and hook up it's GPIO SPI pins (pins 19, 21, 23 and 24, plus pins 1 and 6 for 3.3 volt power).

Use 'flashrom' to upload the image file to the chip. Assuming that the upload and verification succeed, then you can disconnect the programmer, remove the !RESET short on the controller and power everything back up. If anything goes wrong, then the SD diagnostic LED will light up and you'll need to figure out what went wrong and try again.