GPS-710 to Computer Interface

USBGear part number USBG-BAY4 is an Industrial USB to RS-232 serial converter. It uses the FTDI chipset (four independent FT232R chips) and has excellent driver support. I am currently using this hardware with my 64-bit Windows 7 laptop.

Drivers are available for download at http://www.ftdichip.com/Drivers/VCP.htm

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Remove the four screws (two on each side) that hold the top cover in place. Gently lift the top cover, being careful not to bend the red “PWR” LED.

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Remove the four screws that hold the PCB onto the chassis. Remove the four pairs of nuts from the sides of the DB9 ports. The PCB should lift away from the chassis with no difficulty.

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RadioShack sells a 3/32 (2.5mm) jack, part number 274-245, that has a very small footprint. The connections are an “open circuit” design, so when the 2.5mm plug is not inserted the serial ports are available for other uses.

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Carefully locate the hole for the jack, giving clearance to the jack housing, the DB9 connector, and the enclosure. Drill a 9/64” hole and thread the jack through the hole. Tighten the nut to hold the jack in place.

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There are two signals coming from the GPS-710: a TX signal from the GPS, and a TX signal from the TM-D710. These signals need to be connected to the RX pin of two of the serial ports.

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I took a 10” run of CAT5 Ethernet cable and removed the wires from the jacket. I separated three wires from their pairs and restrung them through the jacket. The jacket provides an extra layer of protection where the wires need to bend around the side of the PCB. The ground wire (orange in the picture) can be attached to any of the ground points, but I chose to attach to one of the DB9 mounting points. The PCB is manufactured with lead-free solder (higher melting point than tin/lead), so it takes a stronger soldering iron to make a solid connection. The white haze around the connections in the photo is flux that I hadn’t cleaned before taking the picture.

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Bend the wires around the side of the PCB, leaving some extra wire to make installing the PCB easier. Install the four screws that fasten the PCB to the chassis, but do not tighten. Solder the wires to the 2/5mm jack. Secure the four pairs of nuts into the DB9 connector being careful not to over tighten. After the DB9 nuts are secure, tighten the four screws holding the PCB.

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Reinstall the top cover, watching the alignment with the “PWR” LED. Fasten the top cover with the four screws.

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I connect the GPS-710 to the SerialGear device using a 24” 2.5mm serial cable. These cables, along with a 6” variety, are for sale in the store.

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The trickiest part of the whole deal is determining where Windows has assigned the COM ports. The port assignments can be changed in the Windows “Device Manager” (Control Panel). I have the first port running to the COM port on the back of the Operation Panel. This allows me to use UIView-32 (TM-D710 in packet mode) while I use the GPS data (4800-N-8-1) at the same time. When the laptop isn’t available, I just switch the TM-D710 to APRS mode and I’m ready to roll.

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