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Figure 4 - Initial testing will be done using the evaluation board
Figure 4 - Initial testing will be done using the evaluation board

A GPS module is fairly easy to connect to a microcontroller as long as your supply it with the proper DC power source and know exactly what type of data to expect from the transmit line. If the GPS module includes a "heartbeat" IO pin, then you can simply add a current limiting resistor and an LED to create a visual indicator that will tell you when the GPS module has found a fix and is sending serial data. On my GPS module, the heartbeat IO line is labeled on the datasheet as "1PPS", which means one pulse per second. On power up, this IO line will send out a constant voltage and then blink once per second as soon as the GPS has locked on to as many satellites as it needs in order to create a valid location fix.

To verify the operation of this GPS module, I ordered the evaluation board (Figure 4) from SparkFun, as it included a socket for my GPS and several other popular models. This socket will supply the required DC power to the GPS module and carry all of the other IO lines out to both a solder pad header as well as an RS232 level translator that will allow the data to be received by any computer with a serial port. For PCs without a serial port, a USB to RS232 converter is also included on the board so that data can be received on a virtual com port on the PC. Basically, with the evaluation board you cannot go wrong when it comes to connecting the GPS module up to a computer to read the serial data or send command to the module. It's all plug and play.



Figure 5 - Connecting the FV-M8 GPS module to the evaluation board
Figure 5 - Connecting the FV-M8 GPS module to the evaluation board

Connecting the GPS module to the evaluation board and to a computer was just a matter of plugging in the cables. Since I had a 9 pin serial cable on by test bench for use with my Atmel STK500 programmer, I just moved it from the programmer's socket to the SparkFun evaluation board. I then plugged the FV-M8 into the mating socket on the evaluation board and then added a 12 volt DC jack that had the correct polarity as indicated in the evaluation board datasheet. For USB operation, the board will take power from the USB bus, so no external DC power source would be necessary.

As soon as the power switch was places to the ON position, the status LED on the evaluation board lit up, showing that the GPS module had the proper DC power applied. Since I was using the 9 pin serial connector rather than the USB connector, I set the communication switch on the evaluation board from "USB" to "RS232". The 9 pin serial port labeled "Port1" was then connected to the serial port on my PC using a standard "straight through" serial cable, not a "null modem" cable.

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