High Speed Data Storage for a UAV?
Michael Reno
Posts: 3
Hey everyone,
Recently about two months ago, I began a project to build an autonomous Unmanned Air Vehicle. The aircraft I bought has an 84" wingspan and uses a 3.7 hp engine.
Based on the calculations, a plane this size would need the values from its 10 sensors to be recorded every 10 ms. This is difficult because each sensor needs around .5 ms to be read in by the function RCtime. After this, only about 5 ms are left to save all of these 4 digit numbers. And at a total experiment time of 30 seconds, the date would quickly overflow the stamp's internal memory holds.
There are several different methods for storing data, but each seems to have its own speed bottle neck:
- External EEPROM: Write speed for eeprom is slow
- External RAM: I2C data bus creates delays
- SD Card: Sereal interface also creates delays
I've even considered replacing the BS2px's internal RAM with a larger unit to avoid using an interface protocol.
There are so many options out there I just refuse to believe that there is no good way to do this.
Please let me know if you have any suggestions or if I have to use this thing as a very effective paper weight!
Newbie, Mike
Recently about two months ago, I began a project to build an autonomous Unmanned Air Vehicle. The aircraft I bought has an 84" wingspan and uses a 3.7 hp engine.
Based on the calculations, a plane this size would need the values from its 10 sensors to be recorded every 10 ms. This is difficult because each sensor needs around .5 ms to be read in by the function RCtime. After this, only about 5 ms are left to save all of these 4 digit numbers. And at a total experiment time of 30 seconds, the date would quickly overflow the stamp's internal memory holds.
There are several different methods for storing data, but each seems to have its own speed bottle neck:
- External EEPROM: Write speed for eeprom is slow
- External RAM: I2C data bus creates delays
- SD Card: Sereal interface also creates delays
I've even considered replacing the BS2px's internal RAM with a larger unit to avoid using an interface protocol.
There are so many options out there I just refuse to believe that there is no good way to do this.
Please let me know if you have any suggestions or if I have to use this thing as a very effective paper weight!
Newbie, Mike
Comments
It may be worth looking at the Propeller and the SD card routines written for it ... It works extremely well..
The Parallax Propeller is a·multitasking processor you can let the logging run while dedicating the rest to control etc - there was a discussion in a thread recently where impressive transfer rates were achieved with a bit of 'code tweaking'
That·discussion is here:
http://forums.parallax.com/showthread.php?p=632098
This seems to be·fairly topical with numerous posts - here are a few to see what others are doing with regards to UAV's.
http://forums.parallax.com/attachment.php?attachmentid=46401
http://www.parallax.com/sx/contest/autopilot/Jens-Autopilot2.pdf
http://forums.parallax.com/showthread.php?p=530691
http://forums.parallax.com/showthread.php?p=645854
just fyi http://search.parallax.com·- is a better search tool for the forum ..
Regards,
·········· QuattroRs4
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'Necessity is the mother of invention'
Post Edited (QuattroRS4) : 7/15/2007 3:58:09 AM GMT
Post Edited (Mike Green) : 7/15/2007 3:06:45 AM GMT
Btw, that search link is so useful.
~ Mike