hw_ntc.h File Reference

NTC hardware-specific definition. More...

#include "ntc_map.h"
#include <cfg/debug.h>
#include <drv/ntc.h>
#include <drv/adc.h>

Go to the source code of this file.


Functions

res_t ntc_hw_read (NtcDev dev)
const NtcHwInfo * ntc_hw_getInfo (NtcDev dev)

Detailed Description

NTC hardware-specific definition.

Version:
Id
hw_ntc.h 1359 2008-05-26 09:42:37Z asterix
Author:
Francesco Sacchi <batt@develer.com>
A NTC acts as a variable resistor, whose resistance changes as a function of the temperature it measures. To sample it correctly, it is usually parallelized and serialized with two fixed resistor. The following diagram shows what is the exact disposition of the components, as handled by this library:

                 o Vref
                 |
                 |                               o Vref
                 |                               |
               -----                             |
              |     |                        ---------
              | Rser|                       |         |
              |     |                       |         |
               -----     -----              |   ADC   |
                 | Vp   |     |             |         |
      -----------|------| Amp |-------------|         |
     |           |      |     |      Vadc   |         |
   -----       -----     -----               ---------
  |     |     |     |
  | NTC |     | Rpar|
  |     |     |     |
   -----       -----
     |           |
     |           |
   -----       -----
    ---         ---
 *
Amp is an amplifier that amplify of AMP times the signal. If we indicate Rp as the parallel of NTC with Rpar, ADCBITS as the bits of the ad converter and ADCVAL as the result from the adc convertion (Not Vadc but just the value read from the adc register), after various calculation, the expression of Rp is:



            ADCVAL * Rser
 Rp = ------------------------
         ADCBITS
	2         * AMP - ADCVAL
 *

And after that NTC obvisiously is: 
        Rpar * Rp
 NTC = ----------
        Rpar - Rp
 *

The function ntc_hw_read() compute the resistence using these formulas above. 

Definition in file hw_ntc.h.


Function Documentation






      

        

          const NtcHwInfo* ntc_hw_getInfo           
          (
          NtcDev 
           dev          
           ) 
           [inline]
        

      








Return the info (aka the table) associated with ntc device dev. 

Definition at line 129 of file hw_ntc.h.











      

        

          res_t ntc_hw_read           
          (
          NtcDev 
           dev          
           ) 
           [inline]
        

      








Read the resistence of ntc device dev. Return the result in res_t type. 

Definition at line 113 of file hw_ntc.h.