Kenji Arai / Mbed OS Nucleo_RTC_battery_bkup_pwr_off_okay

In the past, you need modify rtc_api.c in mbed-dev source code. From this revision, you can just use RTC function all of conditions (Normal, Reset, Stand-by, Power OFF).

Note

From now on, you do NOT need any modification for mbed-dev library because STM team updates rtc_api.c source code and support RTC function under reset & standby condition includes power off condition (You need additional VBAT back-up hardware).

Please refer following NOTE information.
/users/kenjiArai/notebook/nucleo-series-rtc-control-under-power-onoff-and-re/

Diff: main.cpp

Revision:
4:a9cebfe4715f
Parent:
3:7b3edf54c706
Child:
5:bc464a588c2e
--- a/main.cpp	Wed Feb 18 09:15:37 2015 +0000
+++ b/main.cpp	Thu Feb 19 02:59:11 2015 +0000
@@ -6,7 +6,7 @@
  *  http://www.page.sannet.ne.jp/kenjia/index.html
  *  http://mbed.org/users/kenjiArai/
  *      Created: January   17th, 2015
- *      Revised: Feburary  18th, 2015
+ *      Revised: Feburary  19th, 2015
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
  * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
@@ -54,6 +54,8 @@
     char buf[42];               // data buffer for text
     time_t seconds;
     uint8_t counter = SHOW_KEY_PROMPT;
+    uint8_t wait_counter = 0;
+    uint8_t xtal = 0;
 
 #if defined(USE_LCD)
     // lcd
@@ -67,10 +69,12 @@
 #endif
     pc.printf("\r\n\r\nTest Nucleo RTC Function\r\n");
     myled = !myled;
-    if (SetRTC() == OK) {
+    if (SetRTC() == 1) {
         pc.printf("External");
+        xtal = 1;
     } else {
         pc.printf("Internal");
+        xtal = 0;
     }
     pc.printf(" Xtal for RTC\r\n");
     show_RTC_reg(); // only for debug purpose
@@ -82,7 +86,11 @@
     while(1) {
         seconds = time(NULL);
         strftime(buf, 40, " %B %d,'%y, %H:%M:%S\r\n", localtime(&seconds));
-        pc.printf("[Time] %s", buf);
+        if (xtal){
+            pc.printf("[Time] %s", buf);
+        } else {
+            pc.printf("[Time by Internal Clock] %s", buf);
+        }
 #if defined(USE_LCD)
         lcd.locate(0, 0);    // 1st line top
         strftime(buf, 40, "%b%d'%y", localtime(&seconds));
@@ -96,6 +104,7 @@
             //      012345678901234567890123456789012345678901234567890123456789012
             pc.printf("Is time correct? If no, hit any key.\r");
         }
+        wait_counter = 0;
         while (seconds == time(NULL)){
             if (pc.readable() == 1){
                 buf[0] = pc.getc();  // dummy read
@@ -116,6 +125,15 @@
                 myled = 0;
                 goto_standby();
             }
+            wait(0.05);
+            if (++wait_counter > (2000 / 50)){
+                if (xtal){
+                    pc.printf("Time was not updated! External Xtal does NOT oscillate.\r\n");
+                } else {
+                    pc.printf("Time was not updated! LSI does NOT work.\r\n");
+                }
+                break;
+            }
         }
         if (counter){
             //         12345678901234567890123456789012345678901234567890