SparkFun Forums 

Where electronics enthusiasts find answers.

Tips and questions relating to the GPS modules from SFE
By Thunderchunk
#17803
Hello. I'm a newcomer here. Great site. I have been spreading the word about it to my fellow computer engineers. I am currently using a variety of Sparkfun products in a project. I am building a GPS device with the ability to pipe the NMEA data through a bluesmirf to feed other devices, and to alert the user when a predefined coordinate is within a certain radius. At this point it is stripping the lat and long out of the NMEA stream and displaying them on an LCD. Everything works great when I hook it up to the breadboard powersupply, but when I try to run off of battery the pic I am using won't output anything, or it outputs garbage now and then. Here are the specifics.

GPS module:
Lassen iQ (Still hooked up to the Evaluation Kit at this stage)

PIC:
18f2550
Running at 4Mhz off of the internal oscillator

Power supply:
2xAA feeding an lt1300 DC-DC converter. (Programable for 3.3 or 5v, currently set at 5v)

LCD:
Serial Enabled 16x2 from sparkfun, backlight off.

The DC-DC converter is rated for 220mA and is providing 5.2 volts, which I am dropping down to 3.3v for the GPS with a regulator. Dopey, I know, but this is a proof of concept. At any rate, the GPS and Bluesmirf work fine off of the battery. I even hooked the LCD straight to the GPS and got readable NMEA data, but whether I try to power the PIC off of 5.2v or the 3.3 volts out of the regulator, no good. The other components continue to work, but I get, at best, a wacky character every second or two on the LCD out of the PIC. Yet, I plug in the breadboard power supply and everything is dandy. Any ideas?