To use the Delorme Tripmate GPS with the TinyTrak modem there are some modifications that must be done to the Tripmate GPS unit.

Please note: Performing this modification to the GPS will void the warranty.

So if you are not confident in your ability to make these modifications I would recommend that you do not attempt this project. Also the author assumes no liability for any damage to the GPS during this modification.

Figure 1 and 1a

The following information describes how to integrate a Delorme Tripmate GPS and a Byonics TinyTrak unit:

The Delorme Tripmate is a first generation GPS unit which outputs $GPRMC NMEA compliant data sentences. Factory re-furbished GPS units are available for $50 plus shipping from Delorme.

TinyTrak has the ability to parse $GPRMC sentences and extract the information, then modulate the data for broadcast to the APRS network. The data is broadcast in MIC-E compressed format. The APRS protocol information may be obtained in the APRS Protocol Document available at the Tuscon Amateur Packet Radio (TAPR) website.

$GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*43

Interpreted as follows:

• RMC Recommended Minimum sentenCe
• 123519 Fix taken at 12:35:19 UTC
• A Status A=active /* The data status. [A] for valid data,[V] for invalid.
• 4807.038,N Latitude 48 deg 07.038' N
• 01131.000,E Longitude 11 deg 31.000' E
• 022.4 Speed over the ground in knots
• 084.4 Track angle in degrees True
• 230394 Date - 23rd of March 1994
• 003.1,W Magnetic Variation /* The difference of magnetic direction from true north.
• *43 The checksum data, always begins with *

The Byonics TinyTrak unit is available in kit form and is very reasonably priced at $25 plus shipping. This kit has easy to follow instructions and may be assembled in an evening if the builder has some experience. It is small enough that it may be placed inside of the Tripmate GPS unit itself. The integration of the TinyTrak into the GPS unit will take another couple of hours. When complete it looks like a very professionally assembled unit. The only permanently connected cable is the output to the tranceiver. I used a 5.5mm coaxial receptical to connect the power to the unit so the power cable may be removed. That way it will minimize the wires hanging out of the unit and make it more easily transportable.

The following additional parts are required to assemble the unit as shown.

• Coaxial Recepticle Radio Shack
• Plus 5 Volt Regulator Radio Shack
• Single Pole Double Throw Switch Radio Shack
• T-1 ¾ LED Holders Radio Shack
• Wire from my Junk Box

For wire I used solid single strand telephone wire. Although it is stiffer that stranded wire I had some available in my junk box so for cost savings I decided to use this and it seemed to work out well.

Delorme GPS Self Start Modification

The Tripmate has 3 modes of operation.

1. OFF - The microprocessor is off, and there is no activity on the unit.
2. Standby - The microprocessor is on and sends the word ASTRAL once a second
3. ON - The microprocessor and receiver are on and the unit is trying to recieve satellites

To turn the Tripmate ON, two things must be done. First it must be placed in STANDBY mode. Then it must hear the word "ASTRAL" on it's serial port. This modification will cause the unit to enter STANDBY mode anytime power is applied, and will cause the Tripmate to hear the word "ASTRAL" so it will turn on it's reciever.

Remove the battery housing, and the metal plate covering the circuit board. Notice the battery plug in the lower left and the 5 wires just to the right along the bottom edge. These wires are from the 9 pin serial connector.

The wires we'll be working on from left to right are as follows:

• Yellow Pin 9 of DB-9 .................. Connects directly to the center of the nylon battery plug
• Black Pin 2 of DB-9 .................... Data out from the GPS
• Brown Pin 3 of DB-9 ................... Data in to the GPS
• Red Pin 4 of DB-9 ....................... DTR used to power GPS on
• Orange Pin 5 of DB-9 ...................Ground

The Red wire was cut off with approximately a one inch long section that was still soldered to the GPS PC board. It is then stripped back about 1/16". It was then soldered to the trace that connect to the top pin on the power recepticle as shown in Figure 2.

The BROWN wire is cut off and jumpered to the connection where the Black wire is soldered to the GPS PC board. Do not unsolder the BLACK wire.

I cut the serial cable off about six (6) inches from the solder connection shown below and then drilled a 1/4" hole in the metal shield that separates the battery compartment from the electronics. The cable was then put through the hole. On the other end of this cable the BLACK and ORANGE wires were soldered to the TinyTrak PC board connected to the serial input (BLACK Wire) and ground (ORANGE Wire) of the card. The YELLOW Wire is not connected to anything on the other end.

Figure 2

The base of the GPS unit is removed and the battery holder is taken out.

Next the TinyTrak PC board is placed inside of the base of the GPS unit to determine the location of the switch and coaxial connector for power. The location of the where the LEDs the 9 Pin DIN connector are to be mounted should be determined. Once these locations are determined, marked and the PC board is then removed while drilling the holes.

Figure 3

The holes for the switch and power jack and 9 pin DIN connector are drilled and trimmed. The LEDs are mounted and silicone sealant is used to hold them in place as shown in Figure 3.

Assembly continues taking special care to double check all work for correctness.

Figure 4

I cut the plug and wires connected to the supplied battery holder and kept them as long as possible so that I could use them to connect the output of a LM-7805 5V regulator to the GPS power plug. The input to the regulator was connected to the 5.5mm coaxial connector where it will then connect to a vehicle cigarette lighter for power. A 5.5mm coaxial recepticle was mounted in the GPS base and is shown in the upper right hand corner of Figure 4.

Figure 5 and 6

The finished project!

73,

de Mike, KI7AB

02/26/2001