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GPS & USB to serial adapter — Parallax Forums

GPS & USB to serial adapter

TumblerTumbler Posts: 323
edited 2008-10-27 03:01 in BASIC Stamp
Is it possible to connect the gps module directly with the adapter (FT232RL) since i have no serial port on my laptop.
I want to use microsoft autoroute 2007 with the gps

Or do i need another adapter?

Regards
Luc

Comments

  • sylvie369sylvie369 Posts: 1,622
    edited 2008-10-12 17:29
    The Parallax GPS module? It outputs serial data at TTL level (correct me if I'm wrong about that...) through a single wire. You can receive those data to a BS2, and then output that through the BS2 serial port (and through the USB-Serial adapter) to your computer, but there's no way to just plug the GPS module into the USB-Serial adapter and send that to the computer.

    As the webpage for the GPS module notes,

    "This device can be connected to a PC serial port using a MAX232 line driver. The circuit isn't supported by Parallax, but it's possible to make this connection with a few dollars of parts."

    I bought a kit to do this, from this site

    http://www.awce.com/rs1.htm?src=gaws

    (man, I'm pretty certain I paid significantly less than $18 for it, though).

    Post Edited (sylvie369) : 10/12/2008 5:37:12 PM GMT
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-10-13 20:06
    Our USB to 232 adapter would not be appropriate in this case because the GPS uses TTL level outputs. Instead I would recommend either the Prop Plug or USB2SER devices we carry to accomplish this interface. Take care.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Engineering
  • TumblerTumbler Posts: 323
    edited 2008-10-14 11:29
    Ah, thanks Chris (and Sylvie)

    I thought the BS2 was programmed with Serial TTL
  • Mark in NHMark in NH Posts: 447
    edited 2008-10-26 22:58
    Hi All,

    ·· I'm looking for schematics and program code to make a BS2 GPS-Datalogger (transmitter-receiver?) for my students to put inside a large (5' tall, 4" diameter) model rocket. We want to track its flight path, where it went, etc.

    I'm not necessarily looking for a bottom-up project (where we learn program language, etc.) but rather, one that students can "build" (wire and connect), fine-tune, and then install in two or three weeks. I'm an 8th grade 'generalist' science teacher, not a tech. ed. teacher or a MIT professor, and·unfortunately my·limited class time doesn't allow the R and·D time we really would need to build it bottom-up.

    Everyone on the forum was really helpful last year when 'we' built a Data-Logger that recorded time, temperature, and humidity to put in a large rocket for an exracurricular activity (www.wearerocketry.org). Profuse thanks to Tracy Allen and Bruce Bates, who were instrumental in getting the project off the ground (no pun intended.) Thanks in advance for your replies.

    Regards from NH,

    Mark

    mkibler@unity.edu
  • sylvie369sylvie369 Posts: 1,622
    edited 2008-10-26 23:22
    5' tall and 4" diameter isn't "large". smilewinkgrin.gif

    One possibility would be to use a Sparkfun datalogger

    http://www.sparkfun.com/commerce/product_info.php?products_id=8627

    and a Parallax GPS module, sending the GPS data through the UART into the datalogger. Here's two reasons why that wouldn't be that great an idea:

    1 - the SD cards pop out of the dataloggers when the ejection charge goes off. Ask me how I know.
    2 - The Parallax GPS module is kinda borderline on the sensitivity needed for this kind of project.

    A better idea would be to use EEPROM for your datalogging (because there's no card to pop out), and a more sensitive GPS receiver like this one:

    http://www.byonics.com/tinytrak/gps.php

    (Byonics GPS2 or 3, depending on how you want to hook it up: same receiver either way). Sparkfun also has a variety of more sensitive GPS receivers. I've been toying with the use of a Byonics Microtrak for rocket tracking, and I've become convinced that you want one of the newer, more sensitive GPS receivers for that purpose. I've got one of the older ones, and while it's fine on the roof or dashboard of a car, it's not so great in a nosecone, especially when a lost track means a lost rocket (in the case of using the Microtrak to transmit the data).

    Oh, by the way, you should probably make this a new thread, rather than putting it on the end of this semi-related thread.
  • Mark in NHMark in NH Posts: 447
    edited 2008-10-26 23:47
    I agree: 5' tall and 4" diameter isn't 'large.' It depends on what you're comparing it to. I didn't want folks on the forum thinking it was an Estes A8-3 rocket.

    'Large' is a full-scale Honest John on an 'O' motor, air-starting to quad M's... or quad 'O's at lift-off! Thanks for the links. I'll check them out.

    Are you from Madison? Did we talk last winter about the TARC/SLI team from Mad West...? We met them at NASA Marshall Space Flight Center last April.

    Mark
  • sylvie369sylvie369 Posts: 1,622
    edited 2008-10-27 03:01
    Mark in NH said...
    I agree: 5' tall and 4" diameter isn't 'large.' It depends on what you're comparing it to. I didn't want folks on the forum thinking it was an Estes A8-3 rocket.

    'Large' is a full-scale Honest John on an 'O' motor, air-starting to quad M's... or quad 'O's at lift-off! Thanks for the links. I'll check them out.

    Are you from Madison? Did we talk last winter about the TARC/SLI team from Mad West...? We met them at NASA Marshall Space Flight Center last April.

    Mark
    I was just ribbing you about the size - I'm not flying anything larger than a 4" diameter rocket myself these days. I'm not from Madison, but I was the guy who posted to your previous thread about the Mad West team. I fly with those guys, and in fact I'll see them this weekend at Midwest Power VI. I'm probably not flying anything though - we're running the range, and I owe quite a bit of range duty.

    I think that your project should be very doable, at least in the datalogging version. Again, get a good, sensitive GPS receiver. If you get one with a serial (DB9) output (like that GPS2 that I linked to) you'll need to attach a male DB9 connector and bring out the +5v, gnd, and TX lines, since I don't think that the BS2 programming port would provide the power properly (if I'm wrong and it does, you'll still need a gender changer, since it'll be female and the programming port is also). Program the BS2 to read in the GPS data - the sample software for the Parallax GPS module should show you how to do that with any GPS receiver that puts out the NMEA $GPGGA string (most of them will):

    http://home.mira.net/~gnb/gps/nmea.html

    Nuts and Volts column #83 has some good stuff on this.

    Take whichever data you need, and use the WRITE command to write them to EEPROM. You'll also need your program to have a "Read data" option so that you can read out the data to your computer after the flight. I'm not sure what the easiest way to do that is, but I'll bet someone here has a brilliant and easy way.

    If you were doing anything other than GPS data, you'd probably need to mess with some kind of timekeeping device as well. But with GPS data, you can just write out the time data from the NMEA string. It'll give you one second accuracy, which is all you're going to get from the GPS receiver anyway (the vast majority of them seem to output their data 1x/second). You're certainly not going to get all sorts of GPS data every 10th of a second on the way up, or anything like that, but it won't matter.


    ·
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