add rtc support
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Mariano Alvira
parent
4d6562a0bc
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c967150038
57
lib/include/rtc.h
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57
lib/include/rtc.h
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/*
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* Copyright (c) 2010, Mariano Alvira <mar@devl.org> and other contributors
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* to the MC1322x project (http://mc1322x.devl.org)
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of libmc1322x: see http://mc1322x.devl.org
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* for details.
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*
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*
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*/
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#ifndef RTC_H
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#define RTC_H
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/* Init RTC (and calibrate, if using ring oscillator) */
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void rtc_init_osc(int use_32khz);
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#ifdef USE_32KHZ
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#define rtc_init() rtc_init_osc(USE_32KHZ)
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#else
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#define rtc_init() rtc_init_osc(0)
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#endif
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/* Calibrate the ring oscillator */
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void rtc_calibrate(void);
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/* Delay for the specified number of milliseconds by polling RTC */
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void rtc_delay_ms(uint32_t msec);
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/* Calibrated frequency of the RTC, in Hz */
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extern int rtc_freq;
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#endif
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202
lib/rtc.c
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202
lib/rtc.c
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/*
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* Copyright (c) 2010, Mariano Alvira <mar@devl.org> and other contributors
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* to the MC1322x project (http://mc1322x.devl.org)
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of libmc1322x: see http://mc1322x.devl.org
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* for details.
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*
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*
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*/
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#include <mc1322x.h>
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#include <stdlib.h>
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#include "rtc.h"
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/* Define USE_32KHZ in board.h to start and use the 32 KHz
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oscillator, otherwise the 2 KHz ring oscillator is used. */
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int rtc_freq = 0;
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static int __use_32khz = 0;
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/* Init RTC */
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void rtc_init_osc(int use_32khz)
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{
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__use_32khz = use_32khz;
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if (use_32khz)
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{
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uint32_t old;
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/* You have to hold its hand with this one */
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/* once you start the 32KHz crystal it can only be
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* stopped with a reset (hard or soft). */
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/* first, disable the ring osc */
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CRM->RINGOSC_CNTLbits.ROSC_EN = 0;
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/* enable the 32kHZ crystal */
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CRM->XTAL32_CNTLbits.XTAL32_EN = 1;
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/* set the XTAL32_EXISTS bit */
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/* the datasheet says to do this after you check that RTC_COUNT
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is changing, but it is not correct; it needs to be set first */
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CRM->SYS_CNTLbits.XTAL32_EXISTS = 1;
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old = CRM->RTC_COUNT;
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while (CRM->RTC_COUNT == old)
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continue;
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/* RTC has started up */
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rtc_freq = 32000;
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}
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else
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{
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/* Enable ring osc */
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CRM->RINGOSC_CNTLbits.ROSC_EN = 1;
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CRM->XTAL32_CNTLbits.XTAL32_EN = 0;
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/* Set default tune values from datasheet */
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CRM->RINGOSC_CNTLbits.ROSC_CTUNE = 0x6;
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CRM->RINGOSC_CNTLbits.ROSC_FTUNE = 0x17;
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/* Trigger calibration */
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rtc_calibrate();
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}
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}
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uint32_t __rtc_try(int loading, int timeout)
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{
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/* Total loading is
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ctune * 1000 fF + ftune * 160 fF
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ctune = 0-15
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ftune = 0-31
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max = 19960 fF
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*/
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#define RTC_LOADING_MIN 0
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#define RTC_LOADING_MAX 19960
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/* The fine tune covers a range larger than a single coarse
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step. Check all coarse steps within the fine tune range to
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find the optimal CTUNE, FTUNE pairs. */
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#define CTUNE_MAX 15
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#define FTUNE_MAX 31
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#define CSTEP 1000
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#define FSTEP 160
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#define MAX_F (FSTEP*FTUNE_MAX) /* actually lcm(CSTEP,FSTEP) would be better,
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but in this case it's basically the same */
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int ctune;
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int ftune;
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int ctune_start = (loading - MAX_F) / CSTEP;
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int ctune_end = loading / CSTEP;
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int best_err = loading, best_ctune = 0, best_ftune = 0;
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uint32_t count;
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if (ctune_start < 0) ctune_start = 0;
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if (ctune_end > CTUNE_MAX) ctune_end = CTUNE_MAX;
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for (ctune = ctune_start; ctune <= ctune_end; ctune++)
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{
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int this_loading, this_err;
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ftune = ((loading - (ctune * CSTEP)) + (FSTEP / 2)) / FSTEP;
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if (ftune < 0) ftune = 0;
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if (ftune > FTUNE_MAX) ftune = FTUNE_MAX;
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this_loading = ctune * CSTEP + ftune * FSTEP;
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this_err = abs(this_loading - loading);
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if (this_err < best_err) {
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best_err = this_err;
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best_ctune = ctune;
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best_ftune = ftune;
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}
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}
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// printf("requested loading %d, actual loading %d\r\n", loading,
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// best_ctune * CSTEP + best_ftune * FSTEP);
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/* Run the calibration */
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CRM->RINGOSC_CNTLbits.ROSC_CTUNE = best_ctune;
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CRM->RINGOSC_CNTLbits.ROSC_FTUNE = best_ftune;
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CRM->CAL_CNTLbits.CAL_TIMEOUT = timeout;
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CRM->STATUSbits.CAL_DONE = 1;
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CRM->CAL_CNTLbits.CAL_EN = 1;
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while (CRM->STATUSbits.CAL_DONE == 0)
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continue;
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/* Result should ideally be close to (REF_OSC * (timeout / 2000)) */
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count = CRM->CAL_COUNT;
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if (count == 0) count = 1; /* avoid divide by zero problems */
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return count;
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}
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/* Calibrate the ring oscillator */
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void rtc_calibrate(void)
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{
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/* Just bisect a few times. Our best tuning accuracy is about
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1/500 of the full scale, so doing this 8-9 times is about
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as accurate as we can get */
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int i;
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int low = RTC_LOADING_MIN, high = RTC_LOADING_MAX;
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int mid;
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uint32_t count;
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if (__use_32khz) {
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rtc_freq = 32000;
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return;
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}
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#define TIMEOUT 100 /* 50 msec per attempt */
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for (i = 0; i < 9; i++)
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{
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mid = (low + high) / 2;
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count = __rtc_try(mid, TIMEOUT);
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// careful about overflow
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rtc_freq = REF_OSC / ((count + TIMEOUT/2) / TIMEOUT);
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if (rtc_freq > 2000)
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low = mid; // increase loading
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else
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high = mid; // decrease loading
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}
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// printf("RTC calibrated to %d Hz\r\n", rtc_freq);
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}
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/* Delay for the specified number of milliseconds by polling RTC */
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void rtc_delay_ms(uint32_t msec)
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{
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uint32_t start;
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start = CRM->RTC_COUNT;
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while ((CRM->RTC_COUNT - start) < ((msec * rtc_freq) / 1000))
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continue;
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}
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