tool/mbed/mbed-sdk/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20XX/rtc_api.c

   1 /* mbed Microcontroller Library
   2  * Copyright (c) 2006-2015 ARM Limited
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 #include "rtc_api.h"
  17
  18 static void init(void) {
  19     // enable PORTC clock
  20     SIM->SCGC5 |= SIM_SCGC5_PORTC_MASK;
  21
  22     // enable RTC clock
  23     SIM->SCGC6 |= SIM_SCGC6_RTC_MASK;
  24
  25     // OSC32 as source
  26     SIM->SOPT1 &= ~SIM_SOPT1_OSC32KSEL_MASK;
  27     SIM->SOPT1 |= SIM_SOPT1_OSC32KSEL(0);
  28 }
  29
  30 void rtc_init(void) {
  31     init();
  32
  33     // Enable the oscillator
  34 #if defined (TARGET_K20D50M)
  35     RTC->CR |= RTC_CR_OSCE_MASK;
  36 #else
  37     // Teensy3.1 requires 20pF MCU loading capacitors for 32KHz RTC oscillator
  38     /* RTC->CR: SC2P=0,SC4P=1,SC8P=0,SC16P=1,CLKO=0,OSCE=1,UM=0,SUP=0,SPE=0,SWR=0 */
  39     RTC->CR |= RTC_CR_OSCE_MASK |RTC_CR_SC16P_MASK | RTC_CR_SC4P_MASK;
  40 #endif
  41
  42     //Configure the TSR. default value: 1
  43     RTC->TSR = 1;
  44
  45     // enable counter
  46     RTC->SR |= RTC_SR_TCE_MASK;
  47 }
  48
  49 void rtc_free(void) {
  50     // [TODO]
  51 }
  52
  53 /*
  54  * Little check routine to see if the RTC has been enabled
  55  * 0 = Disabled, 1 = Enabled
  56  */
  57 int rtc_isenabled(void) {
  58     // even if the RTC module is enabled,
  59     // as we use RTC_CLKIN and an external clock,
  60     // we need to reconfigure the pins. That is why we
  61     // call init() if the rtc is enabled
  62
  63     // if RTC not enabled return 0
  64     SIM->SCGC5 |= SIM_SCGC5_PORTC_MASK;
  65     SIM->SCGC6 |= SIM_SCGC6_RTC_MASK;
  66     if ((RTC->SR & RTC_SR_TCE_MASK) == 0)
  67         return 0;
  68
  69     init();
  70     return 1;
  71 }
  72
  73 time_t rtc_read(void) {
  74     return RTC->TSR;
  75 }
  76
  77 void rtc_write(time_t t) {
  78     // disable counter
  79     RTC->SR &= ~RTC_SR_TCE_MASK;
  80
  81     // we do not write 0 into TSR
  82     // to avoid invalid time
  83     if (t == 0)
  84         t = 1;
  85
  86     // write seconds
  87     RTC->TSR = t;
  88
  89     // re-enable counter
  90     RTC->SR |= RTC_SR_TCE_MASK;
  91 }