Ultimate GPS for UAVs with i2C-gps-nav

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carfreemaine
 
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Ultimate GPS for UAVs with i2C-gps-nav

Post by carfreemaine »

Hello,
Whenever I have a project requiring GPS, the Ultimate GPS Breakout is always my first choice as it is by far the best available option in the price range. However, I now need to incorporate GPS into my MultiWii UAV project which is based on an Arduino Leonardo-type device. According to MultiWii documentation, the processing requirements for using such a high GPS refresh speed over the serial port is too much for the ATMega32u4 to handle, so most people either use either a MEGA2450, a 32 Bit board, or a special processor that converts the GPS signal to i2C.. However, my project parameters are to build a system using as many off-the-shelf and standardized components as possible so I'd rather avoid buying any equipment purpose built for UAVs. Even at such a cheap price range.
Apparently it is possible to roll your own i2C GPS unit using this code- https://code.google.com/p/i2c-gps-nav/ on a Pro Mini to create an i2C slave device.
Has anybody attempted this firmware with the Ultimate GPS breakout? It appears to include a firmware utility for the same chipset, but I don't know if this would clash with the stock firmware that makes it such a great sensor! Would this work?

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Franklin97355
 
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Re: Ultimate GPS for UAVs with i2C-gps-nav

Post by Franklin97355 »

The refresh rate can be set in software to 1hz is this still too fast? Also if you use software serial you can get the readings whenever you want and ignore them when you are doing something else. (I would think as I have not done this myself.)

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carfreemaine
 
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Re: Ultimate GPS for UAVs with i2C-gps-nav

Post by carfreemaine »

Its hard to tell what information is still relevant, but most everything I've read suggests that an extra hardware serial port (e.g Mega2560) is required to handle GPS over Serial on MultiWii.

The usual method for GPS on ATMega328 or 32u4 is to convert the signal to i2C either via an adapter or a slave device using this code https://code.google.com/p/i2c-gps-nav/d ... r&can=2&q=.

To get working on an MTK3339 it needs to be set to 10Hz refresh, with a Baud rate of 115200 and output only GGA, GSA and RMC frames.

I've only found one tutorial outlining how to actually change these settings- http://www.camelsoftware.com/firetail/b ... date-rate/ and it seems particularly complicated for something that should be possible using the many firmware configuration utilities out there.

Am I missing something or does this code need some serious TLC?

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Franklin97355
 
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Re: Ultimate GPS for UAVs with i2C-gps-nav

Post by Franklin97355 »

Am I missing something or does this code need some serious TLC?
Which code are you referencing? The Ultimate GPS is a breakout board for a GPS unit made by GlobalTop Technology Inc. and the data sheet is available here http://www.adafruit.com/datasheets/Glob ... et-V0A.pdf

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carfreemaine
 
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Re: Ultimate GPS for UAVs with i2C-gps-nav

Post by carfreemaine »

franklin97355 wrote:
Am I missing something or does this code need some serious TLC?
Which code are you referencing? The Ultimate GPS is a breakout board for a GPS unit made by GlobalTop Technology Inc. and the data sheet is available here http://www.adafruit.com/datasheets/Glob ... et-V0A.pdf
Sorry, I was referencing this code- https://code.google.com/p/i2c-gps-nav/ which is as far as I know, the only means available to use an MTK3339-based module like the Ultimate GPS, with an Arduino-based UAV flight controller Ala MultiWii/ArduPilot etc... because an 8bit controller requires an i2C connection.

I am commenting on the fact that the code seems to be really old, and options for making the necessary modifications (changing the Baud rate to 115200, the refresh rate to 10Hz and limiting the NMEA output to GGA, GSA and RMC) seem overly complicated considering the availability of various configuration utilities.

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carfreemaine
 
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Re: Ultimate GPS for UAVs with i2C-gps-nav

Post by carfreemaine »

Another related question-
Rather than risk messing with my Full Ultimate GPS Breakout, I went ahead and ordered the bare MTK3339 Chipset as the product page gave the impression that
The module can be soldered by hand without too much difficulty
.

While this may well be true, I didnt realize the solder points are too small for standard perf boards or header pins. Is there a different sized proto PCB/perf board that I can solder this to? If not how would you recommend mounting the chipset?
Again, my intention is to use it with an i2c-slave/Arduino Pro Mini as an i2C-GPS sensor for an RC Flying Wing.

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