[Tinyos Core WG] Meeting: 5/30

[Philip Levis]

On May 30, 2007, at 8:51 AM, Kevin Klues wrote:

> I was thinking a bit about the Read/ReadStream problem and was  
> wondering what everyone thought about creating some sort of generic  
> component that allowed multiple sensors to be grouped together in  
> such a way that it would be guaranteed that they were sampled  
> simultaneously.

"Simultaneously" is a strong word. For example, while the MSP430 ADC  
can be configured to sample a sequence of channels, these samples are  
not actually simultaneous (there is only one ADC, after all). So  
maybe what we really mean is sampling with minimal gaps between the  
samples.

Is is possible that this could be implemented with the current  
interfaces and components, given a better ADC implementation?

For example, let's take the Telos ADC as an example. An application  
issues these three calls in a task:

Read channel 6
Read channel 7
Read channel 11

The ADC will start up the voltage reference. Rather than serialize  
the three calls through a Resource, it's possible to configure the  
DMA to sample the three channels using a sequence.

I don't mean to say that this is the best way to implement the ADC --  
the complexity might be overboard for simple applications. But what I  
wonder is whether the current interfaces are sufficiently expressive  
for a wide range of uses; rather than continue to reinvent new  
interfaces and abstractions, we can also explore the flexibility and  
possible implementations the current ones can support.

Phil