Servo - January 2008

On the cable that I made, I tied both pin 1 and pin 5 together. At this point, you don’t need to connect the PPS or RX pins.

FIGURE 4

FIGURE 5

EM-406A Observations

Of all the modules tested, I found the EM-406 to be the most sensitive and easiest to use. I was able to lock on to four or five satellites in my basement workshop. At times, even the

WAAS receiver kicked in when in the basement. In normal operation outside, I found the EM-406 to be very accurate once the WAAS receiver connected. The only downside was the lack of an external antenna connector. There is no need to send commands to set up the module, so only the TX lead is needed for the interface. I also liked the fact that the module could be operated at five volts. This makes the interface to both the PC and microcontroller very easy.

Etek EB-85A

FIGURE 6

I covered the connector modification in Part 2 of this series. Connect the pins on the connecter as shown in Figure 6. Unlike the EM-406, we need to connect the RX lead as we will need to send some setup commands to the EB-85.

time. This can be a double-edged sword since you have to service the UART more often in order to keep from dropping data.

Holux GPSlim236

leads. Attach the red and black wires to a two-pin header and the green and white leads to a two-pin header as shown in Figure 7. The connection to the Workboard is shown in Figure 8.

Etek EB-85A Observations

The EB-85 operates with five volts as well, so it is one of my favorites. While it does support more channels than the EM-406, I was only able to lock on to seven or eight satellites at a time so I did not see any advantage over the EM-406. The EB-85 does need some setup to turn off some of the messages that are not needed and to turn on the WAAS receiver. The EB-85 sports a much faster default baud rate so more data can be received in a shorter period of

The GPSSlim236 microcontroller interface is simpler than one would think. The mini USB connector on the unit is actually a TTL interface. With this connector, you can both power/charge the unit and pull data from the receiver. I purchased a $3 mini USB cable from www.cyber guys.com (part #131 0995) for the interface.