Diff: targets/TARGET_Freescale/TARGET_K20XX/rtc_api.c

Revision:

0:f269e3021894

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_Freescale/TARGET_K20XX/rtc_api.c	Sun Oct 23 15:10:02 2016 +0000
@@ -0,0 +1,91 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2015 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "rtc_api.h"
+
+static void init(void) {
+    // enable PORTC clock
+    SIM->SCGC5 |= SIM_SCGC5_PORTC_MASK;
+
+    // enable RTC clock
+    SIM->SCGC6 |= SIM_SCGC6_RTC_MASK;
+
+    // OSC32 as source
+    SIM->SOPT1 &= ~SIM_SOPT1_OSC32KSEL_MASK;
+    SIM->SOPT1 |= SIM_SOPT1_OSC32KSEL(0);
+}
+
+void rtc_init(void) {
+    init();
+    
+    // Enable the oscillator
+#if defined (TARGET_K20D50M)
+    RTC->CR |= RTC_CR_OSCE_MASK;
+#else
+    // Teensy3.1 requires 20pF MCU loading capacitors for 32KHz RTC oscillator
+    /* RTC->CR: SC2P=0,SC4P=1,SC8P=0,SC16P=1,CLKO=0,OSCE=1,UM=0,SUP=0,SPE=0,SWR=0 */
+    RTC->CR |= RTC_CR_OSCE_MASK |RTC_CR_SC16P_MASK | RTC_CR_SC4P_MASK; 
+#endif
+
+    //Configure the TSR. default value: 1
+    RTC->TSR = 1;
+
+    // enable counter
+    RTC->SR |= RTC_SR_TCE_MASK;
+}
+
+void rtc_free(void) {
+    // [TODO]
+}
+
+/*
+ * Little check routine to see if the RTC has been enabled
+ * 0 = Disabled, 1 = Enabled
+ */
+int rtc_isenabled(void) {
+    // even if the RTC module is enabled,
+    // as we use RTC_CLKIN and an external clock,
+    // we need to reconfigure the pins. That is why we
+    // call init() if the rtc is enabled
+
+    // if RTC not enabled return 0
+    SIM->SCGC5 |= SIM_SCGC5_PORTC_MASK;
+    SIM->SCGC6 |= SIM_SCGC6_RTC_MASK;
+    if ((RTC->SR & RTC_SR_TCE_MASK) == 0)
+        return 0;
+
+    init();
+    return 1;
+}
+
+time_t rtc_read(void) {
+    return RTC->TSR;
+}
+
+void rtc_write(time_t t) {
+    // disable counter
+    RTC->SR &= ~RTC_SR_TCE_MASK;
+
+    // we do not write 0 into TSR
+    // to avoid invalid time
+    if (t == 0)
+        t = 1;
+
+    // write seconds
+    RTC->TSR = t;
+
+    // re-enable counter
+    RTC->SR |= RTC_SR_TCE_MASK;
+}