[Tinyos-help] Fwd: Regarding tmote sky sampling rate

[Michael Schippling]

I'm cc'ing this back to the help list where someone may have a
better opinion...

I would generally set a repeat Timer in start() like this:
     call Timer.start(TIMER_REPEAT, READMS);
where READMS is something above 3ms (the undocumented minimum in T1).
When the timer fires, start a conversion. Then either chain all the
conversions you want to do so each dataReady() calls the getData() of
the next, or else run a little state machine like you seem to be doing
so each timer firing initiates a different conversion. You'll have to
analyze the timing and settling requirements for your sensors and the
ADC to figure out the best approach.

Using a ONESHOT timer is fine but it just adds more code confusion if
all you want is regular periodic samples. You might want to have a
'watchdog' timer on the data transmission task similar to what you
have commented out (the 5000 period timer) but I've only seen this
to be (possibly) useful on multi-hop systems that fall out of sync.

The "ADC prescalar" stuff is misleadingly named, what it actually does
is set the clock rate of the ADC and thus the time it takes to do a
conversion -- the time between getData() and dataReady(). If you were
free-running the ADC that would set the sample rate.

MS

amit ohri wrote:
> 
> 
> ---------- Forwarded message ---------- From: *amit ohri*
> <ohriamitlit at gmail.com <mailto:ohriamitlit at gmail.com>> Date: Sun, Nov 2, 2008
> at 5:57 PM Subject: Regarding tmote sky sampling rate:Michael Schippling To:
> "Ohri, Amit" <amit.ohri at okstate.edu <mailto:amit.ohri at okstate.edu>> Cc:
> ohriamit_lit at yahoomail.com <mailto:ohriamit_lit at yahoomail.com>
> 
> 
> Hi there My name is Amit and i am working on Tmote sky with Easysen SBT80
> board.I am using oscilloscope application to display sensor signal.The
> sampling rate which I am getting from sensor is 500. Can u please tell me how
> to increase sampling rate. I know that by changing ADC prescalar sampling can
> be changed but I tried but was unsuccessful.I  tried to change ADCcontrol
> interface (cygwin/opt/moteiv/tinyos-1.x/tos/interfaces)for ADC prescalar but
> was not successful. CAn you please guide me regarding the same. I have
> attached the NEsc code which I am using. Can you suggest me more regrading
> the same
> 
> 
> ------------------------------------------------------------------------
> 
> //$Id: Acceleration.h,v 1 2005/10/31 18:48:54 cssharp Exp $
> 
> /* "Copyright (c) 2000-2003 The Regents of the University of California. *
> All rights reserved. * * Permission to use, copy, modify, and distribute this
> software and its * documentation for any purpose, without fee, and without
> written agreement * is hereby granted, provided that the above copyright
> notice, the following * two paragraphs and the author appear in all copies of
> this software. * * IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE
> TO ANY PARTY FOR * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL
> DAMAGES ARISING OUT * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
> IF THE UNIVERSITY * OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGE. * * THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY
> WARRANTIES, * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
> MERCHANTABILITY * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE
> PROVIDED HEREUNDER IS * ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA
> HAS NO OBLIGATION TO * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS,
> OR MODIFICATIONS." */
> 
> //@author Amjad Awawdeh <amjad.awawdeh at okstate.edu> & Jakkrit Kunthong
> <jakkrit at okstate.edu>
> 
> 
> // X Acceleration enum { TOS_ADC_XACC_PORT = unique("ADCPort"),
> 
> TOSH_ACTUAL_ADC_XACC_PORT = ASSOCIATE_ADC_CHANNEL( INPUT_CHANNEL_A1, 
> REFERENCE_VREFplus_AVss, REFVOLT_LEVEL_2_5 ) };

-- 
Platform: WinXP/Cygwin
TinyOS version: 1.x, Boomerang
Programmer: MIB510
Device(s): Mica2, MicaZ, Tmote
Sensor board: homebrew