[Tinyos-help] Questions about ADC

[Ernest Andrew McCracken (emccrckn)]

Fixed.

From: tinyos-help-bounces at millennium.berkeley.edu [mailto:tinyos-help-bounces at millennium.berkeley.edu] On Behalf Of Ernest Andrew McCracken (emccrckn)
Sent: Tuesday, June 23, 2009 1:01 PM
To: tinyos-help at millennium.berkeley.edu
Cc: Lan Wang (lanwang)
Subject: [Tinyos-help] Questions about ADC

Hi I have a few questions concerning the ADC software components.  The platform we use is the telosb.   Maybe someone knows or can point me in the right direction.

First Question:

According to TEP 101 the MSP430 has several selectable reference voltage combinations.  These can be set using AdcConfigure interface.  I want to be able to use 'AVcc and (Vref-)' but I do not know the value that corresponds to this for the parameter sref in :

typedef struct
{
  unsigned int inch: 4;            // input channel
  unsigned int sref: 3;            // reference voltage
  unsigned int ref2_5v: 1;         // reference voltage level
  unsigned int adc12ssel: 2;       // clock source sample-hold-time
  unsigned int adc12div: 3;        // clock divider sample-hold-time
  unsigned int sht: 4;             // sample-hold-time
  unsigned int sampcon_ssel: 2;    // clock source sampcon signal
  unsigned int sampcon_id: 2;      // clock divider sampcon signal
} msp430adc12_channel_config_t;

Does anyone know what value corresponds to Avcc and Vref- ?

Second Question:

Currently we are using the AdcReadStreamClient to read a single channel at high sampling frequencies.  However I have found that I cannot sample faster than 1.8 kHz.  According to the MSP430 User's Guide the ADC is capable of 200+ ksps.  I have found that the AdcReadStreamClient uses component Msp430Adc12ClientAutoRVGC. I have also found the component Msp430Adc12ClientAutoDMA_RVGC which copies samples using DMA.  This later component should enable me to sample faster correct?  If so does anyone know of any implementations of this component in an application that I can look at.  If not does anyone know of any other techniques that could enable faster sampling from the ADC?

Ernest McCracken
Research Assistant
Networking Research Laboratory
Computer Science Department
University of Memphis


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