How Fast

Rob · 09-23-2002, 05:05 PM

Borrowed a GPS the other day, to calibrate my speedo.

Grate fun can be had driving along country lanes trying to mentain a constant speed

Ironically it's seems that I have the only acurate speedo that Rover ever made, it was shocking spot on undr 40 and only out by 1mph above.

However the mileage was totaly out, and I'm pleased to say the my car has done 5k less than the clock reads

Does any one know what these units are like to interface to, as I wouldn't mind having a 7 segment display on my dash to give me an exact read out of my speed.

:edit: Not a mis-spelling this time, I wrote completely the wrong word instead.

eugenen · 09-23-2002, 06:24 PM

Depends on the GPS. They are usually a serial port and most output a NEMA format. You could use a small microcontroller to build a serial receiver and dsiplay the data or feed it into a pc and drive a display from there.

Zip-Lock · 09-24-2002, 12:14 PM

Where could one find information on using a microcontroller to display that data?

eugenen · 09-24-2002, 12:49 PM

Its going to depend on your microontroller
Pic's are populat so you can go to microchip's site and look in the app notes. You will need to take the code from the rs232 app note and the display one and then look up the protocol on the NEMA's site

Krazy Nemesis · 09-29-2002, 01:23 PM

Parallax used to have a GPS application note I could point you to. But I think they took it down after the whole 9/11 thing. Don't want terrorists building self guiding projectiles!!!

I'm eventually going to work on an app that will read my Earthmate and display info onto a 40x4 LCD, and buffer the data to my computer, so I can use my computer as well. Hopefully both at the same time. I'll be using a Scenix chip though, instead of a pic. But if your asking questions like this, I'd recommend trying your hand at the Basic Stamp or the BasicX. At $50, both are a little expensive for my taste (I'm such a cheap bastard I absolutely had to learn Assembly). Pic's and the Scenix chips are considerably cheaper at under $10 a pop.

Zip-Lock · 09-29-2002, 03:57 PM

Wow I really am interested in learning how to program BASIC stamps. I have heard about them over the years but I have never bought a kit and got started, it's something I want to get into.

My questions so far are:

1. I'm looking for a starter kit. I was looking at Parellax's Board of Education is that a good one?

2. I think I will need to use a BASIC stamp II. They only have one serial port. I want to take the GPS data (requiring one serial port) and display it on an LCD (I have a serial LCD so it will require another serial port) how can I get two serial ports out a stamp? Do I need two?

SuperMatty · 09-29-2002, 04:26 PM

I'm interested in using microcontrollers to hook up various sensors in my car. Where is a good place to start? I'm very familiar with C++. Any book recommendations or kits?

eugenen · 09-29-2002, 07:14 PM

Its been a while since I have had time for programming microcontrollers, sold my pic programmer a few years ago. I learned assemby, on 8051, 68k, and 8088 as well as c and pascal in college. played with the pics some and the 68hc11. I kind of like the form factor of the stamps, everyhting combined on one, but their not real flexible and i don't want to mess with basic, would rather just do the pic assembly, or parallax's 8051 like assembly

Krazy how did you find the protocol of the earthmate. I have one but am looking for a standard NEMA GPS because of the propritary protocol of the earthmate.

Krazy Nemesis · 09-29-2002, 11:58 PM

Zip-Lock - The Basic Stamp can actually transmit and recieve on ALL of it's i/o pins. So technically it has 16 serial in/outs, 1 out only and 1 in only. The board of education is probably what you will want to start with. Just remember that all of the publications that they sell online are also available for download, so don't pay for anything that you can just print out.

(again, I'm a cheap bastard!)

Eugenen - I haven't figured out the protocol for the Earthmates yet. But I haven't tried. I don't think it's encrypted or anything, but I do know it's binary not ascii. Shouldn't take me more than a couple hours to figure it out once I get a dump.

Krazy Nemesis · 09-30-2002, 12:27 AM

Quote:

Originally posted by SuperMatty
I'm interested in using microcontrollers to hook up various sensors in my car. Where is a good place to start? I'm very familiar with C++. Any book recommendations or kits?

Sorry dude, didn't see your question. Umm... I don't know much about it, but check out this compiler/tokenizer for the Scenix chips. I use these chips, but program using the free assembly compiler.

But I think it would be worth your while to check out the Basic Stamps. The PBasic codes that it uses is truly very simple to understand, especially if you are already familiar with programming.

Charliey · 10-02-2002, 05:10 PM

I read somewhere that you can get the nmea protocol from nmea, but its not a free protocol, and it costs lots to get the spec book for it.

Edit: i found the page for it:
http://www.nmea.org/pub/0183/index.html
its $250 for the protocol book. Good luck analysing the output.

Krazy Nemesis · 10-02-2002, 05:33 PM

The NMEA standard is ASCII output only, and I already have access to the standards. You can look around on the internet to find the basics that are needed.

The Earthmate however outputs in a binary format, which would look like garbage in a terminal program (as opposed to a well formated NMEA output). It has a few extra things that it can do that 'standard' NMEA wont, like gps location, signal strength and tracking information, Etc.