Re: [Libnifalcon-devel] Libnifalcon-devel post from radarsat1@gmail.com requires approval

[Stephen S. <rad...@gm...>]

Hi!

On Sun, Apr 27, 2008 at 2:15 PM, Kyle Machulis (qDot)
<ky...@no...> wrote:
> Ok, just made a huge step on the drivers, unfortunately borne out of me
> ignoring my own notes.

It happens... :)
For a while my wireless card would only work at 11 Mbps until the
driver author realized he'd made a < / <= typo in the code...


I've heard of this 16 ms / 64 byte thing regarding FTDI chips.  It
always made me wonder how they managed to do high-speed stuff using
these chips actually.  Glad to know it can be set to 1.  I think I
figured that they were instead just padding the data to get it to fill
the 64-byte buffer and transmit faster.

I modified findfalcons to do some timing tests with the following code:

   time_last = time_sec;
   gettimeofday(&now,NULL);
   time_sec = (now.tv_sec%10000) + now.tv_usec/1000000.0;
   diff_sec = time_sec - time_last;
   diff_avg = (diff_avg*(count-1) + diff_sec)/count;

   if ((count%100)==0)
   {
       printf("time diff: %f, frequency = %f    "
               "average: %f, %f\n",
               diff_sec, 1.0/diff_sec,
               diff_avg, 1.0/diff_avg);
   }


There were my results without this recent change:

time diff: 0.015991, frequency = 62.534351    average: 0.016000, 62.498571
time diff: 0.015991, frequency = 62.534351    average: 0.016000, 62.498578
time diff: 0.015991, frequency = 62.534351    average: 0.016000, 62.499364
time diff: 0.015930, frequency = 62.773946    average: 0.015998, 62.508708
time diff: 0.016052, frequency = 62.296578    average: 0.015998, 62.506211
time diff: 0.016052, frequency = 62.296578    average: 0.015999, 62.505367

And *with* the set_latency call:

time diff: 0.001953, frequency = 512.000000    average: 0.002040, 490.245333
time diff: 0.002075, frequency = 481.882353    average: 0.002015, 496.184239
time diff: 0.002075, frequency = 481.882353    average: 0.001967, 508.398800
time diff: 0.001953, frequency = 512.000000    average: 0.001910, 523.534142
time diff: 0.001953, frequency = 512.000000    average: 0.001852, 539.941967
time diff: 0.000977, frequency = 1024.000000    average: 0.001807, 553.513720
time diff: 0.001953, frequency = 512.000000    average: 0.001764, 566.752401


Very nice!
That's pretty much haptic speed now... One tricky thing being that
there is a lot of jitter.
Does the D2XX driver really perform faster than that?  I know it
should really be 1000 Hz.


Great stuff.  I'm hoping to spend some time soon playing with the
motors to see how well I can control them.


Steve