Differences

This shows you the differences between two versions of the page.

--- projects:parafoil:two [2007/06/04 21:02] – rocketboy
+++ projects:parafoil:two [2008/07/19 23:33] (current) – external edit 127.0.0.1
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   * Aerocomm 868Mhz Radio
   * Cutdown device
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 GPS is a cheap Jupiter Rockwell GPS unit that was bought off ebay for £10, its relatively large for a gps unit but out puts at TTL so can easily be wired up to the gumstix's TTL serial ports. Information about the pinouts etc can be found [[http://www.gpskit.nl/gps-readme.html|here]]. As a warning the rockwell jupiter has annoyingly spaced pins which require a special socket so instead of that hassle using a soldering iron i removed the pins and directly soldered wires to the holes that the pins sat in originally :-D. Also this hack reduces the height of the gps making it easier to intergrate.
-The GPS requires an antenna which attaches with a mcx connector - I also got one of these off ebay (you can also get them from maplins) - the cable was far to long so i shortened it by cutting a section out and resoldering the two ends being careful to keep the different bits of the coax cable seperate. I used an active antenna so added a power line from the gumstix. One thing i've noticed is when the gps is powered on and the gumstix is off the nmea pulses seem sufficient to cause the gumstix light to flash in time. Doesn't seem to effect the gumstix but will require some more investigation (perhaps something to do with the common ground). //eeeek - I suspect you will find that this the gumstix being partly powered via the input pin protection diodes - the gps output will be higher than the gumstix Vdd - hence the protection diode will try to pull the Vdd up - generally not good for the GPIO port :-< -  to stop this happening either power on the gumstix first or wire both the gumstix and the GPS behind a common power switch. Alternativlty a small resistor (about 270ohm should provide some protection) - rocketboy //
+The GPS requires an antenna which attaches with a mcx connector - I also got one of these off ebay (you can also get them from maplins) - the cable was far to long so i shortened it by cutting a section out and resoldering the two ends being careful to keep the different bits of the coax cable seperate. I used an active antenna so added a power line from the gumstix. One thing i've noticed is when the gps is powered on and the gumstix is off the nmea pulses seem sufficient to cause the gumstix light to flash in time. Doesn't seem to effect the gumstix but will require some more investigation (perhaps something to do with the common ground). //eeeek - I suspect you will find that this the gumstix being partly powered via the input pin protection diodes - the gps output will be higher than the gumstix Vdd - hence the protection diode will try to pull the Vdd up - generally not good for the GPIO port :-( -  to stop this happening either power on the gumstix first or wire both the gumstix and the GPS behind a common power switch. Alternativlty a small resistor (about 270ohm should provide some protection) - rocketboy //
 On the software side the gps is connected to BTUART and therefore ttyS1 - A perl script is used to read the gps and log to /gps.log - exactly as is done with the Pegasus missions.