Playing with the SUP500F GPS module

The SUP500F is a pretty nice unit: small, low power consumption (33mA), 10Hz update, and quick start up time (29 second cold start with an open sky).

Here it is on the breadboard:

I’m using a MAX232 to convert the RS-232 voltages from the PCs serial port to TTL (5V), and a simple voltage divider to reduce the 5V TTL signal to the 3V required by the SRF500F’s UART.

Initially there was no signal on the TX pin, and a square wave with a 4 second period on pin 6 (the documentation states this pin should have a frequency of 1Hz). This behaviour was reported by a couple of other people on the sparkfun forum. After a bit of trial and error I got the expected behaviour by setting VBAT to +5V, and PSE_SEL to GND.

If you view the serial port output with something like TeraTerm (9600 baud 8N1) you can see the NMEA messages streaming out of the GPS unit:


If you like your GPS data to look a bit prettier, you can use the SkyTraq GPS Viewer software available on the SparkFun website:

It took about 5 minutes under an open sky for it to get a fix the first time, but since then its been very fast: 30 seconds if its been off for more than 30 minutes or so, and under 5 seconds otherwise. The initial delay is because the GPS unit has to download the almanac (a coarse description of all satellite orbital information, valid for a few months), and the ephemeris for each visible satellite (a precise description of the satellite’s orbital and clock correction information, valid for 30 minutes).

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One Response to Playing with the SUP500F GPS module

  1. Pingback: GPS, in the library, with a hammer | Stainless Steelhead

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