Zahid:
Let me reiterate: you cannot do busy wait in TOSSIM. TOSSIM is a
discrete event simulator. Because of the fact that it is a discrete
event simulation, all tasks will take zero (simulated) time to
execute. Time does not advance during execution of events (tasks), but
only between the events (tasks).
> do{
> if(flag){
> var = 1;
> }
> cT = sim_time();
> }while(cT < initial_time + PULSE_WIDTH);
What your code is trying to do is waiting for the simulated time to
advance. Clearly, this won't work, because the (simulated) time does
not change while executing a task. (Remember? Executing a task is
instantaneous, i.e. it takes zero (simulated) time.)
Should this be still unclear after reading the TOSSIM paper, I suggest
that you google for "discrete event simulation".
Janos
On Mon, Apr 20, 2009 at 1:59 PM, zahid iqbal <[email protected]> wrote:
> Many thanks, Janos ...
>
> I had a hint from the assembly code that BusyWaitMicroC was meant for the
> actual hardware. But your comments clarified a lot.
>
> I want to introduce the delays of Microseconds. For that, the problem with
> using Timer Interfaces is the following:
>
> Though, timer interfaces provide TMilli and TMicro, there is not TimerC
> available for TMicro precision.
> I want my code to block until a certain time has elapsed. In this sense,
> even if I use a timer (Say a micro timer implementation is available), I
> will do, startOneShot, ... but my program would just continue its way after
> making a call to startOneShot, ... it would not block on that.
> Imagine another scenario, in which I want to constantly check some variable
> in a finite loop, where loop is indexed by time. That is, the loop should
> exit after a certain amount of time, but while in loop, I have to check and
> set some variables. I tried doing the following
>
> #define PULSE_WIDTH 250000 // 25 micro seconds, in terms of
> simulation ticks
> sim_time_t initial_time, current_time;
> initial_time = sim_time();
> do{
> if(flag){
> var = 1;
> }
> cT = sim_time();
> }while(cT < initial_time + PULSE_WIDTH);
>
>
> This solution does not work, since the program gets stuck.....
>
> Any idea, what could be nice solution for me, --- Do, I have to use threads
> ??
>
> Thanks for your time,
>
>
> Regards,
> zahid iqbal
>
>
>
>
>
> --- On Mon, 4/20/09, Janos Sallai <[email protected]> wrote:
>
> From: Janos Sallai <[email protected]>
> Subject: Re: [Tinyos-help] Problem using BusyWaitMicroC
> To: "zahid iqbal" <[email protected]>, "tinyos forum"
> <[email protected]>
> Date: Monday, April 20, 2009, 11:50 AM
>
> Zahid,
>
> TOSSIM is a discrete event simulator, that is, tasks are assumed to
> execute instantaneously. Having a busy wait in your code will make no
> difference: you can spin as long as you wish in a loop, the simulated
> execution time of the task will still be zero. If you don't understand
> what the above means, make sure that you read the TOSSIM paper (
> http://www.cs.berkeley.edu/~pal/pubs/nido.pdf ).
>
> Because of this, there is no BusyWaitMicroC implementation for the sim
> target. What you try compiling in is for the avr target (with some avr
> assembly code inlined). Since this assembly code is not for the x86
> target, the compiler complains.
>
> You have two options:
> - Use timers for waiting. This works well in TOSSIM, and not that hard
> to implement.
> - Use a cycle-accurate simulator (e.g. avrora). Be aware that this is
> much slower than TOSSIM.
>
> Janos
>
> On Mon, Apr 20, 2009 at 6:35 AM, zahid iqbal <[email protected]> wrote:
>> Hi,
>>
>> I am writing a simulation in TOSSIM under tinyos-2.1.0.
>>
>> In my application, I have to introduce some delays, in the order of
>> microseconds. I am using,
>>
>> BusyWait.nc
>> BusyWaitMicroC.nc
>>
>> Whenever I compile, I get the following error.
>>
>> /opt/tinyos-2.1.0/tos/platforms/micaz/BusyWaitMicroC.nc: In function
>> ‘BusyWaitMicroC$BusyWait$wait’:
>> /opt/tinyos-2.1.0/tos/platforms/micaz/BusyWaitMicroC.nc:40: error:
>> impossible constraint in ‘asm’
>>
>> I don't understand this, since I am not much familiar with assembly
>> coding.
>> Can this be because of using a wrong BusyWaitMicroC for my interface.
>> Please
>> note:
>>
>> I use the following width and precision,
>>
>> uses interface BusyWait<TMicro, uint16_t>;
>>
>> I am simulating for micaz platform and hence I use "make micaz sim". It is
>> probably because of this reason, that my compiler picks BusyWaitMicroC
>> from
>> /tos/platforms/micaz/BusyWaitMicroC.nc
>>
>> What can be the problem here,
>>
>> Any help will be much appreciated.
>>
>> Regards,
>> zahid iqbal
>>
>>
>>
>>
>>
>> _______________________________________________
>> Tinyos-help mailing list
>> [email protected]
>> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
>>
>
>
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