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00001 /* 00002 * Copyright (c) 2010, Mariano Alvira <mar@devl.org> and other contributors 00003 * to the MC1322x project (http://mc1322x.devl.org) 00004 * All rights reserved. 00005 * 00006 * Redistribution and use in source and binary forms, with or without 00007 * modification, are permitted provided that the following conditions 00008 * are met: 00009 * 1. Redistributions of source code must retain the above copyright 00010 * notice, this list of conditions and the following disclaimer. 00011 * 2. Redistributions in binary form must reproduce the above copyright 00012 * notice, this list of conditions and the following disclaimer in the 00013 * documentation and/or other materials provided with the distribution. 00014 * 3. Neither the name of the Institute nor the names of its contributors 00015 * may be used to endorse or promote products derived from this software 00016 * without specific prior written permission. 00017 * 00018 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND 00019 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 00020 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 00021 * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE 00022 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 00023 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 00024 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 00025 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 00026 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 00027 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 00028 * SUCH DAMAGE. 00029 * 00030 * This file is part of libmc1322x: see http://mc1322x.devl.org 00031 * for details. 00032 * 00033 * 00034 */ 00035 00036 #include <mc1322x.h> 00037 #include <stdlib.h> 00038 #include "rtc.h" 00039 00040 /* Define USE_32KHZ in board.h to start and use the 32 KHz 00041 oscillator, otherwise the 2 KHz ring oscillator is used. */ 00042 00043 int rtc_freq = 0; 00044 static int __use_32khz = 0; 00045 00046 /* Init RTC */ 00047 void rtc_init_osc(int use_32khz) 00048 { 00049 __use_32khz = use_32khz; 00050 00051 if (use_32khz) 00052 { 00053 uint32_t old; 00054 00055 /* You have to hold its hand with this one */ 00056 /* once you start the 32KHz crystal it can only be 00057 * stopped with a reset (hard or soft). */ 00058 00059 /* first, disable the ring osc */ 00060 CRM->RINGOSC_CNTLbits.ROSC_EN = 0; 00061 00062 /* enable the 32kHZ crystal */ 00063 CRM->XTAL32_CNTLbits.XTAL32_EN = 1; 00064 00065 /* set the XTAL32_EXISTS bit */ 00066 /* the datasheet says to do this after you check that RTC_COUNT 00067 is changing, but it is not correct; it needs to be set first */ 00068 CRM->SYS_CNTLbits.XTAL32_EXISTS = 1; 00069 00070 old = CRM->RTC_COUNT; 00071 while (CRM->RTC_COUNT == old) 00072 continue; 00073 00074 /* RTC has started up */ 00075 rtc_freq = 32000; 00076 } 00077 else 00078 { 00079 /* Enable ring osc */ 00080 CRM->RINGOSC_CNTLbits.ROSC_EN = 1; 00081 CRM->XTAL32_CNTLbits.XTAL32_EN = 0; 00082 00083 /* Set default tune values from datasheet */ 00084 CRM->RINGOSC_CNTLbits.ROSC_CTUNE = 0x6; 00085 CRM->RINGOSC_CNTLbits.ROSC_FTUNE = 0x17; 00086 00087 /* Trigger calibration */ 00088 rtc_calibrate(); 00089 } 00090 } 00091 00092 uint32_t __rtc_try(int loading, int timeout) 00093 { 00094 /* Total loading is 00095 ctune * 1000 fF + ftune * 160 fF 00096 ctune = 0-15 00097 ftune = 0-31 00098 max = 19960 fF 00099 */ 00100 00101 #define RTC_LOADING_MIN 0 00102 #define RTC_LOADING_MAX 19960 00103 00104 /* The fine tune covers a range larger than a single coarse 00105 step. Check all coarse steps within the fine tune range to 00106 find the optimal CTUNE, FTUNE pairs. */ 00107 #define CTUNE_MAX 15 00108 #define FTUNE_MAX 31 00109 #define CSTEP 1000 00110 #define FSTEP 160 00111 #define MAX_F (FSTEP*FTUNE_MAX) /* actually lcm(CSTEP,FSTEP) would be better, 00112 but in this case it's basically the same */ 00113 int ctune; 00114 int ftune; 00115 int ctune_start = (loading - MAX_F) / CSTEP; 00116 int ctune_end = loading / CSTEP; 00117 int best_err = loading, best_ctune = 0, best_ftune = 0; 00118 00119 uint32_t count; 00120 00121 if (ctune_start < 0) ctune_start = 0; 00122 if (ctune_end > CTUNE_MAX) ctune_end = CTUNE_MAX; 00123 00124 for (ctune = ctune_start; ctune <= ctune_end; ctune++) 00125 { 00126 int this_loading, this_err; 00127 00128 ftune = ((loading - (ctune * CSTEP)) + (FSTEP / 2)) / FSTEP; 00129 if (ftune < 0) ftune = 0; 00130 if (ftune > FTUNE_MAX) ftune = FTUNE_MAX; 00131 00132 this_loading = ctune * CSTEP + ftune * FSTEP; 00133 this_err = abs(this_loading - loading); 00134 if (this_err < best_err) { 00135 best_err = this_err; 00136 best_ctune = ctune; 00137 best_ftune = ftune; 00138 } 00139 } 00140 00141 // printf("requested loading %d, actual loading %d\r\n", loading, 00142 // best_ctune * CSTEP + best_ftune * FSTEP); 00143 00144 /* Run the calibration */ 00145 CRM->RINGOSC_CNTLbits.ROSC_CTUNE = best_ctune; 00146 CRM->RINGOSC_CNTLbits.ROSC_FTUNE = best_ftune; 00147 CRM->CAL_CNTLbits.CAL_TIMEOUT = timeout; 00148 CRM->STATUSbits.CAL_DONE = 1; 00149 CRM->CAL_CNTLbits.CAL_EN = 1; 00150 while (CRM->STATUSbits.CAL_DONE == 0) 00151 continue; 00152 00153 /* Result should ideally be close to (REF_OSC * (timeout / 2000)) */ 00154 count = CRM->CAL_COUNT; 00155 if (count == 0) count = 1; /* avoid divide by zero problems */ 00156 return count; 00157 } 00158 00159 /* Calibrate the ring oscillator */ 00160 void rtc_calibrate(void) 00161 { 00162 /* Just bisect a few times. Our best tuning accuracy is about 00163 1/500 of the full scale, so doing this 8-9 times is about 00164 as accurate as we can get */ 00165 int i; 00166 int low = RTC_LOADING_MIN, high = RTC_LOADING_MAX; 00167 int mid; 00168 uint32_t count; 00169 00170 if (__use_32khz) { 00171 rtc_freq = 32000; 00172 return; 00173 } 00174 00175 #define TIMEOUT 100 /* 50 msec per attempt */ 00176 00177 for (i = 0; i < 9; i++) 00178 { 00179 mid = (low + high) / 2; 00180 count = __rtc_try(mid, TIMEOUT); 00181 // careful about overflow 00182 rtc_freq = REF_OSC / ((count + TIMEOUT/2) / TIMEOUT); 00183 00184 if (rtc_freq > 2000) 00185 low = mid; // increase loading 00186 else 00187 high = mid; // decrease loading 00188 } 00189 00190 // printf("RTC calibrated to %d Hz\r\n", rtc_freq); 00191 } 00192 00193 00194 /* Delay for the specified number of milliseconds by polling RTC */ 00195 void rtc_delay_ms(uint32_t msec) 00196 { 00197 uint32_t start; 00198 00199 start = CRM->RTC_COUNT; 00200 while ((CRM->RTC_COUNT - start) < ((msec * rtc_freq) / 1000)) 00201 continue; 00202 }