Using Parallax GPS with Propeller

Paul Voss

Hi,

Does anyone have a piece of code (spin or propeller assembly) that will read in the Parallax GPS module in its Smart mode? I would also be interested in a more detailed description of the one-wire communications protocol (apparently in a document called AppMod). I can't seem to find this information on Parallax site (or on google).

Paul

Leon

Try the Maxim/Dallas web site for one-wire docs. Dallas invented it.

Leon

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sylvie369

The Parallax GPS module doesn't use a "one-wire interface". It uses a serial interface, 4800 baud, non-inverted.

From the documentation:

Some Parallax person said...
The GPS Receiver Module is controlled by the host via an easy-to-use, TTL-level, asynchronous serial communications interface. The command structure and communication is compatible with Parallax’s AppMod serial protocol. The single SIO pin transfers commands sent TO the Module and data received FROM the Module. All communication is at 4800bps, 8 data bits, no parity, 1 stop bit, non-inverted.

It does transmit and receive on the same pin, but that's not a "one-wire" protocol. When you say "one-wire", people will assume you're referring to a specific protocol - as Leon did here.

en.wikipedia.org/wiki/1-Wire

What you need is an object to use a Propeller serial object (probably SimpleSerial, possibly FullDuplexSerial) to communicate with the Propeller. The Propeller will send an "attention" string ("!GPS"), then a command byte (there's a table of them in the GPS docs), and then read a number of bytes in return into your GPS variables. It should be a pretty straightforward matter for someone who knows what he's doing - define all of the commands as constants, define variables to hold the returned data, set up the communications with an Init method, etc.

Post Edited (sylvie369) : 11/29/2008 2:34:36 PM GMT

GaryT

Hi Paul,

I found the attached files somewhere, I forgot where, but I think it's doing smart mode using a single wire, I don't think it's Onewire protocol, just a clever way of doing async serial using the same wire for both directions.

Hope it helps,
Gary T