[Tinyos-2.0wg] TinyOS 2.x WG/07.5.2006 Meeting Notes

[henri dubois-ferriere]

> Phil:
>
>
> lets talk about ImmediateRequest.
> AR says not needed.
>
> David:
> Henri is using it.
>
> Kevin:
> I could not understand his code. He is not going back to request if the
> first call fails
>


in some cases (in particular in XE1205PhyP) there just isn't much
reason to do a split-phase request if immediaterequest fails, because
by the time the granted comes back to give you the bus it will be too
late to be of any use, i.e., the radio fifo will have over-flowed (in
rx; in tx it will have underflowed).

The timing constraints are 1 byte time at 76kbps: 100us, which melts
away pretty quickly once you throw in atomic overhead, latency to
transfer first byte over SPI, etc.

OT: As a historical aside the radio can in fact do 152kbps and after a
lot of pain i managed to get the 1.x stack running solidly at that
speed; but in 2.x (at least when i implemented the driver back in jan)
overhead of things like SPI or arbiters was had grown just enough that
i had to put the max bit rate at 76k.

>
> ImmediateRequest does not carry a lot of overhead now
>
> David:
> sounds like a good solution
>
> Kevin:
> for evaluation we need to talk to Henri
>
> David:
> goes to EPFL, can talk with him
>
>  Phil:
> it might be in the serial
>
> All:
> and the radio
>
> Phil:
> Kevin, can you write this up?
>
> Kevin:
> yes
> no overhead if no PM
>
> Phil:
> ADC/SID alignment issue
> problem when we want to use them at lower levels
> SID TEP requires values to be left shifted
> this is problematic at lower levels when we don't have the info
> solution: interface should not specify this
> sensor boards TEP will specify this
> HAL2 will use interfaces without this
> Jan looks to be fine with the decision
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