[Click] Accurate timers with polling Tasks: Help a newbie?

[g91d5350 at campus.ru.ac.za]

Hi Clickers

I'm working on a TDM-style multi-hop MAC.  I know that a number of  
other people have done similar stuff, so hopefully there will be an  
easy answer to my question.

I'm hoping to achieve a TDM slot size of around 1ms.  In order to do  
this, I'll need to be able to time packet transmissions, and measure  
their arrival times, to microsecond-accuracy.

 From what I understand, Click timers are based on the Linux clock  
which ticks at about 1Khz in 2.6 kernels (giving a resolution of about  
1ms) which is not accurate enough for my needs.

The documentation for the timer class tells me:
"..there can be a significant delay between a Timer's nominal  
expiration time and the actual time it runs. Elements that desire  
extremely precise timings should combine a Timer with a Task. The  
Timer is set to go off a bit before the true expiration time (see  
Timer::adjustment()), after which the Task polls the CPU until the  
actual expiration time arrives."
... which sounds like just the sort of thing I need.

But I am a newbie to Click, and I'm daunted by the thought of having  
to write the Task polling code.

I want:
* Code to transmit a packet at a regular interval (say every 1ms, to  
accuracy of 100us or better)
* Code to read the arrival time of a packet to us accuracy (I'm not  
there yet, but I think this should be easy...)

Can anybody help me with some sample code?  This must have been done, surely?

Thanks
- Kevin Duff
PhD Candidate, Rhodes University
Wireless Mesh Researcher, Meraka Institute