Stroller <[email protected]> [14-10-12 09:28]:
>
> On Sat, 11 October 2014, at 3:10 pm, [email protected] wrote:
> > ...
> > Two things need still to be investigated: How can I store GPSdata onto the
> > flash in a way, that no additional data is stored if no movement is
> > there.
>
> This should be pretty easy, but if you want help with it, you're going to
> need to give us some insight into how you're storing or accessing the GPS
> data at present.
>
> Having said that, I'm not convinced that this is necessary. I have a logfile
> here with 91,000 lines of text in it, and it's 9.9mb and bzips down to 369kb.
> 91,000 is close to 10 entries every minute for a week, and I'd guess that
> you'd find CSV formatted GPS data written as text to have about the same
> length and compressibility as a typical /var/log/messages entry.
>
> > And I have to prevent, that a sector/block/organisation unit
> > of the flash is written more than once to prevent ware out of the
> > flash.
>
> Wear-levelling should be handled by the flash memory controller, and you
> shouldn't need to worry about it.
>
> Stroller.
>
>
>
Hi Stroller,
thank you for your input :) !!
I am still a pure newbie to gps. This morning I discovered, that there
a LOT of kinds of output of the different GPS devices...the output of
mine looks /so standard/, that I thought it would be /THAT STANDARD/.
;)
Ok ... the device I use is an Ultimate GPS by Adafruit Industries.
The device is a GlobalTop-FGPMMOPA6C module with a MediaTek MT3339
chipset.
The output are NMEA sentences (pure ASCII as it seems). The module is
wired to UART01 on my embedded computer, so gpsd can read the data
from /dev/ttyO1.
Via gpsd it is possible to create json output from that (instead of
NMEA).
The module creates from 1 to 10 position reports per second. I want
to make this speed depended (read: I have to write some code for it,
if I dont find some...). If one choose 1 report/second it will send
5 position report and then 1 status report (current time for example).
Since civil GPS modules have the feature to obfuscate the exact
position up to some degree (otherwise I would build a weapon instead
of tinkering with an embedded system...at least according to some
external laws ;) I see problems in deciding, whether I am really
moving or my position is moving due to """less accuracy of the
chipset""".
Currently the GPS antenna is clamped to my desktop lamp and I am
nearly up to 100% sure that it is not moving at all...but gpsmon gives
me a natural speed of 0.5km/h which is definitely too much for
a warmth induced Brownian molecular motion... ;)
"Wear levelling should be handled by the flash memory controller..."
This "should" makes me a little nervous, Stroller... ;)
Linux includes a filesystem called F2FS, which takes care
of the wear levelling problem (as far as I know). This F2FS originates
from SAMSUNG, one of the greater manufacturer of Flash memories of all
kind. Why the effort, if the memory controller take care of it?
Stroller, I DONT EXPLICETLY OR IMPLICITELY EXPRESS A "I DONT BELIEVE
YOU" HERE...!
It is just the difference between what manufacturer states ("...should be
handled...") and what mechanisms create more benefits for them.
Best regards,
mcc
