136 lines
4.4 KiB
C
136 lines
4.4 KiB
C
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/**
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* \file
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* <!--
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* This file is part of BeRTOS.
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*
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* Bertos is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* As a special exception, you may use this file as part of a free software
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* library without restriction. Specifically, if other files instantiate
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* templates or use macros or inline functions from this file, or you compile
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* this file and link it with other files to produce an executable, this
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* file does not by itself cause the resulting executable to be covered by
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* the GNU General Public License. This exception does not however
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* invalidate any other reasons why the executable file might be covered by
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* the GNU General Public License.
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*
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* Copyright 2008 Develer S.r.l. (http://www.develer.com/)
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* All Rights Reserved.
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* -->
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*
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* \brief NTC hardware-specific definition
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*
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* \author Francesco Sacchi <batt@develer.com>
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*
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* A NTC acts as a variable resistor, whose resistance changes as a
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* function of the temperature it measures. To sample it correctly, it is
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* usually parallelized and serialized with two fixed resistor. The following diagram shows
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* what is the exact disposition of the components, as handled by this
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* library:
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*
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*<pre>
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* o Vref
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* |
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* | o Vref
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* | |
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* ----- |
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* | | ---------
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* | Rser| | |
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* | | | |
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* ----- ----- | ADC |
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* | Vp | | | |
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* -----------|------| Amp |-------------| |
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* | | | | Vadc | |
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* ----- ----- ----- ---------
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* | | | |
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* | NTC | | Rpar|
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* | | | |
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* ----- -----
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* | |
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* | |
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* ----- -----
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* --- ---
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*</pre>
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* Amp is an amplifier that amplify of AMP times the signal.
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* If we indicate Rp as the parallel of NTC with Rpar, ADCBITS as the bits of the ad converter
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* and ADCVAL as the result from the adc convertion (Not Vadc but just the value read
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* from the adc register), after various calculation, the expression of Rp is:
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*
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*<pre>
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*
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* ADCVAL * Rser
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* Rp = ------------------------
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* ADCBITS
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* 2 * AMP - ADCVAL
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*</pre>
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*
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* And after that NTC obvisiously is:
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*<pre>
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* Rpar * Rp
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* NTC = ----------
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* Rpar - Rp
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*</pre>
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*
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*
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* The function ntc_hw_read() compute the resistence using these formulas above.
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*/
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#ifndef HW_NTC_H
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#define HW_NTC_H
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#include "ntc_map.h"
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#include <cfg/debug.h>
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#include <drv/ntc.h>
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#include <drv/adc.h>
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#warning TODO:This is an example implementation, you must implement it!
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extern const res_t NTC_RSER[NTC_CNT];
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extern const res_t NTC_RPAR[NTC_CNT];
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extern const amp_t NTC_AMP[NTC_CNT];
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extern const NtcHwInfo* NTC_INFO[NTC_CNT];
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/*!
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* Read the resistence of ntc device \a dev.
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* Return the result in res_t type.
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*/
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INLINE res_t ntc_hw_read(NtcDev dev)
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{
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ASSERT(dev < NTC_CNT);
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// See above for formula explanation.
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adcread_t adcval = adc_read((uint16_t)dev);
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float rp = (adcval * NTC_RSER[dev] ) / ((1 << adc_bits()) * NTC_AMP[dev] - adcval);
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//kprintf("Rp[%f], Rntc[%f]\n", rp/100, ((NTC_RPAR[dev] * rp) / (NTC_RPAR[dev] - rp)) / 100.0);
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return ( (NTC_RPAR[dev] * rp) / (NTC_RPAR[dev] - rp) );
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}
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/*!
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* Return the info (aka the table) associated with ntc device \a dev.
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*/
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INLINE const NtcHwInfo* ntc_hw_getInfo(NtcDev dev)
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{
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return NTC_INFO[dev];
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}
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#define NTC_HW_INIT do { /* Implement me! */ } while(0)
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#endif /* HW_NTC_H */
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