gps module circuit diagram needed

August 5, 2008 1:56 PM

can you help me locate a circuit diagram of a gps module on internet?

title says it all.

i googled and searched but could not find any sources. is it top secret or am i not looking close enough? the ones i have found are gps kits with already commercially available modules. but i want the module itself.

posted by raphael19 to technology (5 comments total)

It is not clear exactly what you are looking for. Do you want just a block diagram or actual schematics. The title doesn't say it all. Perhaps explaining your purpose would help. A GPS module includes proprietary designs that cost millions of dollars to develop. No one is going to just hand that over to you. The module includes proprietary chipsets which were not designed as schematics at all, but instead using a Hardware Description Language. In order to get information about how to use the chipsets you would need to develop a business relationship with the chipset vendor and sign a non-disclosure agreement. Without access to the chipset, a schematic wouldn't do you any good.
posted by JackFlash at 2:18 PM on August 5, 2008

You aren't going to find a 'schematic' that doesn't have some sort of proprietary IC's at it's heart, because ultimately the guts of GPS are in the software that turns the radio waves from the satellites into usable information. As you can see here, the CPU is just a generic PIC16C73A "8-Bit CMOS Microcontrollers with A/D Converter". It's the programming that goes along with the hardware that turns this from just a (tiny) bunch of raw processing power, into a GPS module.
posted by nomisxid at 2:20 PM on August 5, 2008

As you probably know, there are a few suppliers who sell complete self-contained GPS modules - Navsync is one. If you look at some data sheets (eg CW 20), you can see pinouts.

Or this and this from Maxim, which is a complete system, including schematic.
posted by Artful Codger at 2:27 PM on August 5, 2008

Have you looked at Sparkfun ? They sell a number of GPS modules with schematics...
posted by plinth at 3:02 PM on August 5, 2008

I think nomisxid is mistaken about the purpose of the circuit shown in the pdf he links to. That circuit uses the "one pulse per second" (1PPS) output that some GPS receivers have to produce an output signal at precisely 5MHz. It is not a GPS receiver circuit.

The Maxim documentation may be more what you're looking for -- the GPS receiver consists of an antenna, signal conditioning, and a "GPS Baseband DSP" -- that is, a blob of hardware and software that decodes the GPS signal and produces position and time data.

The wikipedia article on GPS signals links to the actual specification of the GPS signals IS-GPS-200D.

There is also an effort to write the GPS signal decoder as Free (GPL) software: GPL-GPS. This may give you some ideas as to the nature and complexity of the signal processing in a GPS receiver. It doesn't seem to be a ready-to-assemble project, however.
posted by jepler at 5:37 PM on August 5, 2008