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About corosplat

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  1. Just to clarify.. when you say simple half-wave dipole, you mean like the one in the RC-CAM4 project? Made from coax stripped to the right length with the shield folded back. At 868MHz the elements would be about 8.2cm long for a total length over 16cm right? Does it matter how much "extra" coax I have besides the antenna element itself or is that a trial and error thing. Also as for mounting in the plane, I guess it would be best to have it pointing down, but given the length, would it be OK to lay it flat, or at least angle it back? thanks,
  2. Thanks for the tips, I'll check it out. I've since found this PCB antenna here http://www.siretta.co.uk/search_box.php?mcatid=49 which looks interesting. What do you think about that type?
  3. Hello, I'm looking for ideas for an antenna on the airborne side of a UAV project to connect to an Aerocomm AC4868-250 radio modem module (mmcx antenna connector). It would be nice to get a commercial unit, but the ones I have found so far are a bit large and clumsy for integration in a small UAV. Home-brew copper foil/coax projects are also of some interest. /Steve
  4. Thanks, there are some host controller chips for embedded systems listed here http://www.lvr.com/usb.htm#HostSoftware with the full protocol stacks implemented, but that solution seems a bit overkill for a simple camera controller. I agree, a fake host probably has a low chance of success, and it would be difficult to debug such a project. I'm sure things will get better when this USB on-the-go protocol gets going. You could make quite a handy little gadget for controlling all sorts of camera functions. I'll keep it in the back of my mind and watch for developments. cheers
  5. Hi, at the risk of exposing my ignorance, I want to throw an idea out for discussion: I have been thinking a lot about the possibility of controlling a camera through the USB port with a pic-chip or similar remote switch to avoid opening it up and soldering to the switch traces. I lurked a bit on the USB developers forum but notice that whenever anyone asks a question like this, they get ridiculed for their lack of understanding of USB and taken out back and flogged with the 300-page USB protocol manual . OK so now I understand that the USB spec does not allow for devices to talk to eachother directly, there must be a host on the bus to manage the data flow. The protocol stack is way too heavy to implement on a simple microcontroller, and the physical layer must be handled in hardware. But I still wonder how hard can it be to trick a camera into *thinking* it is connected to a host computer and send it the command blocks to do simple things like trigger the shutter? I'm not talking about a USB compliant plug-and-play thing... this is a pure hack to control the camera. Maybe you could use a USB-enabled PIC chip to handle the physical layer with all its timing complexities. You can probably even discard most of the data that the camera sends back. Some smart guys with USB-sniffers and a lot of time have already figured out the command sequences for canon cameras here: http://www.graphics.cornell.edu/~westin/ca...anon/index.html and the Gphoto project has more than 400 cameras listed http://www.gphoto.org/ the challenge would be to get the camera to think it is talking to a host computer and send the command blocks in the right way. I am not sure if there is some fundamental reason why this wouldn't be possible. Is there a difference between a host-side and device USB controller for example. any thoughts? cheers,
  6. From the NMEA faq at http://vancouver-webpages.com/peter/nmeafaq.txt The optional checksum field consists of a "*" and two hex digits representing the exclusive OR of all characters between, but not including, the "$" and "*". A checksum is required on some sentences. Other useful GPS info at http://vancouver-webpages.com/peter/
  7. Whoa Mike.. you're way ahead of me here OK, I didn't get your program to work on XP, but no matter. I confirmed pretty much the same thing with another program I had. that is, the GPS in NMEA mode will listen to a $GPWPL sentence and mark a waypoint at that location. Great, that's a start, but as you say,what we really need is a NMEA command to say "mark waypoint at current location". I think they call it a 'man overboard' function. But I don't see anything like that in the NMEA protocol (or the garmin protocol). A little device would have to listen to the gps, keep a current position in memory, and then feed it back into the GPS as a waypont on command. You might be able to get a bit fancy and interpolate between two records to get a more accurate position. cheers
  8. Thanks for the suggestion Matt. I had wanted to avoid a separate storage device and make use of the GPS's memory to store the waypoints. But I'll take your word for it that it is tricky to control the GPS from the outside with a simple microchip. I might be able to get away with just recording the time a photo is taken and synchronize with the GPS clock somehow.
  9. Greetings, I have been messing around with R/C aerial photography and live video for some time and just recently had my first GPS-equipped flight. I was thinking it would be really useful to mark a GPS waypoint every time you take a photo so you can position them on a map later. You could maybe use the same chip that triggers the camera to control the GPS. I use a Garmin geko201 and had a quick look through the garmin communication protocol but couldn't find a simple way to do it. So the question is if anyone has done this already, and if there is an undocumented command that marks a waypoint at the current location? Cheers
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