Thread Tools
This thread is privately moderated by Jack Crossfire, who may elect to delete unwanted replies.
Apr 17, 2008, 01:05 PM
Registered User
Jack Crossfire's Avatar
Thread OP
Discussion

Fire, smoke, & lenses


Got lucky with the crash damage. Only $25 & 5 hours of repairs. Remarkably, the main shaft didn't bend. Got the computer running again. The tiny hirose connector was predicted to break in it's first opportunity, & it did. Now we know where to pad the computer.

Got the serial port reading SiRF binary, 9600 baud, & low latency, thanks to Canadia. U need to set c_cc[VMIN] to 1 & c_cc[VTIME] to 1. Now we know the binary protocol gives much more accurate readings than NMEA.

Discovered if U have multiple BEC's, only connect 1 of the ground lines. Reversing the polarity of the computer tap causes a short circuit between +12V from the ground & +6V from the BEC. That's what melted a wire https://www.rcgroups.com/forums/showthread.php?t=812551 before. Now the remaining unmelted RCE-BL35X wires are 6V & PWM. The computer's diode protects the +12V line but not the ground.

The answer is yes, using SiRF binary protocol gives much more accurate readings than NMEA. Got good results using the 3 module network. The 1 module network was disappointing. Still have more combinations to try before declaring the 622Mhz a waste of money.

Web 2.0 is getting back to full power after a few months of mass layoffs, & lots of middle managers R getting promoted. The bigger the manager, the smaller the car. Spending almost all day in traffic. Monster accidents shut down the freeway all morning. More accidents stopped traffic all night. Only getting 15 minutes of test flights.

3 modules
current GPS acceleration
current tilt
|
\/
future GPS acceleration


1 module
current GPS acceleration
current MEMS acceleration
current tilt
|
\/
future GPS acceleration
Last edited by Jack Crossfire; Apr 17, 2008 at 01:28 PM.
Sign up now
to remove ads between posts
Apr 18, 2008, 07:44 AM
Don L.
Got the serial port reading SiRF binary, 9600 baud, & low latency, thanks to Canadia. U need to set c_cc[VMIN] to 1 & c_cc[VTIME] to 1. Now we know the binary protocol gives much more accurate readings than NMEA.


Jack,

I've been following your excellent work with great interest, even though I'm not currently building a UAV.

I'm curious about your comment on SiRF binary. Are you suggesting that the data are more accurate, or that the SiRF protocol is better for parsing the data?

- Don
Apr 18, 2008, 04:03 PM
Registered User
Jack Crossfire's Avatar
Thread OP
The binary protocol uses X, Y, Z coordinates to the meter for location & velocity. The NMEA protocol uses latitude, longitude, altitude to a fixed number of decimal places. The smallest NMEA decimal places convert to slightly more than a meter for location & velocity.
Apr 20, 2008, 07:58 AM
Don L.
Quote:
Originally Posted by Jack Crossfire
The binary protocol uses X, Y, Z coordinates to the meter for location & velocity. The NMEA protocol uses latitude, longitude, altitude to a fixed number of decimal places. The smallest NMEA decimal places convert to slightly more than a meter for location & velocity.
Thanks for clearing that up, Jack.

I can live with NMEA for my purposes, which is simply to log altitude and position of aerial images - would like have something faster than 1 second updates, though.


Quick Reply
Message:
Thread Tools