Intuitive Circuits GeoStamp Audio User manual

GeoStamp® Audio
Copyright © 2003 Intuitive Circuits, LLC
GPS to Audio Encoder

Description
GeoStamp®Audio converts GPS receiver latitude, longitude, heading, speed, altitude,
date, and time into a continuous audio stream that can be recorded by devices such
as video camcorders. The audio output track, matched with the video recording, translates
into an exact, permanent record of where and when events occur. The GeoStamp®Audio
RS-232 serial output is a reconstruction of the original NMEA 0183 GPRMC and
GPGGA sentences from the GPS receiver. This serial output can be used by numerous
applications such as computer based GPS mapping software. GeoStamp®Audio supports
all NMEA 0183 compatible GPS receivers such as the Garmin GPS35-PC.
GeoStamp®Audio includes a cigarette plug, wall transformer, and null-modem
serial cable.
Specifications
Dimensions: 4.25" x 3.50" x 1.25"
Weight: 6.5 oz.
Input voltage: 8.0 to 14.0 volts DC (20 ma max.)
DC jack: 2.1 mm x 5.5 mm, center tip positive
Operating temperature: -10 C to +70 C
GPS input: NMEA 0183 4800 baud GPRMC and/or
GPGGA sentences
Serial output: 4800 baud, 8 data bits, no parity, one stop bit
Audio modulation: FSK
Audio output level: -10dB +/- 1dB
Audio input level range: -40.0 to -8.0 dBV
Acceptable audio signal to noise ratio: 20.0 dB
Connections
GeoStamp®Audio has four connectors (see figure 1.0.)
Connector Hookup
AUDIO IN • Only used for decode mode
• Attach to the audio output source that will play back the
• previously recorded GPS audio stream
AUDIO OUT • Only used for encode mode
• Attach to an audio recording device such as a video camcorder
• external microphone, left or right audio input
GPS / PC •
For encode mode attach to the GPS receiver RS-232 serial output
• For decode mode use the supplied null-modem cable attached •
to a computer RS-232 serial port
DC IN • +8 to +14 volts DC
• 2.1 mm x 5.5 mm DC coax plug, center tip positive
2

3
Configuration
GeoStamp®Audio has two configuration options, both are on the circuit board.
To open the enclosure remove the two back screws, remove the panel and bezel,
and slide the circuit board out.
GPS sentence selection
GeoStamp®Audio uses two internal jumpers to select which NMEA 0183 GPS
sentences (GPRMC and/or GPGGA) will be encoded. The sentence encoding rates
are once per second so if both jumpers are installed (default) then the GPRMC
sentence is encoded, followed by the GPGGA sentence the next second.
Audio output level adjustment
The audio output of level of GeoStamp®Audio can be adjusted via the output level
pot VR1. GeoStamp®Audio support both mic and line level outputs. Adjust the
audio output level to match your recording device.
Operation
Both encoding and decoding modes require a 8-14 VDC source. A cigarette plug is
supplied for field use and a wall transformer for office use.
Encoding mode
GeoStamp®Audio defaults to encoding. Upon applying power GeoStamp®Audio
scans for GPS NMEA 0183 data from the GPS receiver which must be connected to
the GeoStamp®Audio GPS / PC serial jack. The resulting audio encoded GPS data
is sent through the GeoStamp®Audio AUDIO OUT jack.
Decoding mode
Attach the supplied null-modem cable from GeoStamp®Audio GPS / PC serial jack to
a computer RS-232 serial port. The RS-232 protocol is 4800 baud, 8 data bits, no parity,
and one stop bit. To enter the decoding mode hold down the GeoStamp®Audio
DECODE button on the front panel and apply power to GeoStamp®Audio. Continue
holding the DECODE button for 3 or more seconds and then release. While valid
encoded audio is received on the GeoStamp®Audio AUDIO IN jack the reconstructed
NMEA 0183 GPRMC and GPGGA sentences are sent out the GeoStamp®Audio
GPS / PC serial jack.
Fig 1.0 - Back view of GeoStamp®Audio.

Intuitive Circuits, LLC
2275 Brinston
Troy, MI 48083
Voice: [phone]
Fax: [phone]
http://www.icircuits.com
Trouble Shooting Tips
Problem
Green LED off (won’t power up)
No encoded audio is generated
(only a constant tone is generated
from the audio out jack)
No serial output is generated in
decode mode
Warranty & Service
If the product fails to perform as described in our product description or specification,
within 90 days from the date of shipment to the buyer, we will repair or replace the
product and/or accessories originally supplied. Failure due to improper installation,
misuse, abuse or accident is not covered by this warranty. Incidental and consequential
damages are not covered by this warranty. The buyer must obtain a Return Material
Authorization by calling [phone], and shipping the defective product to
Intuitive Circuits, 2275 Brinston, Troy, MI 48083, freight prepaid. After the warranty
expires, we will promptly supply an estimate for the repair cost.
Solution
• Verify power supply output (8 to 14 VDC).
• Verify polarity of supply.
• Verify the 250 ma internal fuse is good.
• Verify encode mode selected.
• Verify valid GPS signal is being received.
• Verify decode mode selected.
• Verify valid encoded audio being received.
• Adjust the encoding audio output level (VR1).