1 /* mbed Microcontroller Library
2 * Copyright (c) 2006-2015 ARM Limited
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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
18 static void init(void) {
20 SIM->SCGC5 |= SIM_SCGC5_PORTC_MASK;
23 SIM->SCGC6 |= SIM_SCGC6_RTC_MASK;
26 SIM->SOPT1 &= ~SIM_SOPT1_OSC32KSEL_MASK;
27 SIM->SOPT1 |= SIM_SOPT1_OSC32KSEL(0);
33 // Enable the oscillator
34 #if defined (TARGET_K20D50M)
35 RTC->CR |= RTC_CR_OSCE_MASK;
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;
42 //Configure the TSR. default value: 1
46 RTC->SR |= RTC_SR_TCE_MASK;
54 * Little check routine to see if the RTC has been enabled
55 * 0 = Disabled, 1 = Enabled
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
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)
73 time_t rtc_read(void) {
77 void rtc_write(time_t t) {
79 RTC->SR &= ~RTC_SR_TCE_MASK;
81 // we do not write 0 into TSR
82 // to avoid invalid time
90 RTC->SR |= RTC_SR_TCE_MASK;