[time-nuts] Needed: The Real Serial USB Fix
Bob Camp
lists at rtty.us
Sat Aug 24 11:35:39 UTC 2013
Hi
On Aug 24, 2013, at 3:27 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
>
>> If it were me, I remove the LCD display. I don't see a need when everyone
>> today has a phone. the little AVR chip can bit-bang a UDP packet once per
>> second and put it on your wifi router. That cuts the parts cost by 1/3rd
>> and the display will be where you can see it, on the phone or computer.
>
> There are still a few of us who don't have cell phones. :(
>
> I split the problem into two areas:
> Collecting the data
> Displaying it
>
> If I'm collecting data, I want to be able to look back over hours, days,
> months, or even years. That means I probably want to backup/archive it too.
>
> 100 characters of text every 10 seconds is under a megabyte per day. That's
> small relative to modern disks, medium relative to thumb drives or SD cards
> and small to medium relative to RAM (or ramdisk). [I generally chop things
> up into a file per day.]
That's a *lot* more than a simple monitor. Once you get past "simple" you already have LH and a lot of hardware that will run it just fine.
Bob
>
> So far, I've always had a handy Linux box running 24x7 when I wanted to
> collect data, so I've never tried to use a smaller system. Since the data is
> collected on a real system, it's easy to display it any way I like.
>
> I won't be surprised if a project comes along where I want something like a
> small uP to grab careful timing data. Until then, I'll keep collecting my
> data on a real PC.
>
> ------------
>
> Does anybody have data on lifetime of Thumb/SD cards if you flush a log file
> every 10 seconds?
>
> What type of file systems are supported with whatever OS comes with small
> uPs? Is there any work on flash-friendly file systems for append-only log
> files?
>
> A year or 3 ago, I did some work on logging to ramdisk and occasionally
> copying to hard disk. The idea was that the hard disk would be spun-down
> most of the time, saving a lot of power. It didn't save much so I bailed on
> that project. I assume that means the power to keep the disk spinning is low
> relative to the power to keep the electronics going. Maybe I just botched
> the experiment.
>
>
> flushing the file after each line is the simple way to make (mostly) sure
> that your data gets to disk in case the system crashes, but it turns into
> several disk writes each "line". That's no big deal for a lightly loaded
> hard drive but gets interesting in terms of total writes to flash drives.
>
> You could, of course, fix the code to only do the flush once every N minutes,
> or only when something interesting happens...
>
>
> --
> These are my opinions. I hate spam.
>
>
>
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