[Tinyos-help] Re: DAC on telosb

Poornima Jayarao pjayarao at yahoo.com
Tue Sep 20 16:34:40 PDT 2005


Hi Joe,

Thanks again. Here is some feedback:

Changing the SINE_PERIOD = 1 ms, and 
using the MSP430TIMER_ACLK in timerprepare
yields a nice sinewave on the scope with
the following parameters:
(scope I have is old, so only coarse measurements)
(Unloaded, i.e. DAC0 not driving any speaker etc)

DC bias of output: 1.24V
AC swing = +/- 0.66V 
DC offset = 0.250V
Phase shift between end of current sine and next =
0.5ms.

Regards
pj

--- Joe Polastre <joe at polastre.com> wrote:

> > Q1: Does the TestDAC12 output on DAC0 pin?
> 
>   As per the configuration:
> 
>   Impl.DAC -> MSP430DAC12C.DAC0;       // use DAC0
> 
> > Q2: How do I change TestDAC12M.nc to keep
> > the DAC outputing the sine wave continuously?
> > Or does it already do that? Sorry I cannot
> > figure it out.
> 
>   It outputs continuously.
> 
>   async event void DMA.transferDone(result_t s){
>     atomic {
>       call Leds.yellowToggle();
>       call DMA.startTransfer();
>     }
>   }
> 
> > Q3: If a speaker is connected to DAC0 pin,
> > without an amplifier, will I be able to
> > observe the sine wave on a scope?
> 
> Yes.
> 
> -Joe
> 


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