fixes

avr_code/max31329.c

@@ -31,8 +31,12 @@ RTC_RFM69_STATUS set_time_from_rfm69(identifier_results id_data)
             TIME.Year = RX_DATA.msg[5];
             TIME.Wday = RX_DATA.msg[6];
 
-            rtc_write_time(TIME);
-            return RTC_RFM69_SET_TIME_SUCCESS;
+            // Only claim success once the time actually landed in the RTC,
+            // so a failed write is retried next cycle.
+            if (rtc_write_time(TIME) == 0) {
+                return RTC_RFM69_SET_TIME_SUCCESS;
+            }
+            LOG("RTC write failed\n");
         }
     }
     return RTC_RFM69_SET_TIME_FAILED;
@@ -78,8 +82,16 @@ uint8_t rtc_read_time_array(uint8_t* data)
 
 time_struct rtc_read_time(void)
 {
+    if (rtc_read_time_array(DATA_BUFFER_7)) {
+        // RTC unreachable: mark every field with an unmistakably invalid value
+        // rather than transmitting whatever was read last. The base station
+        // sees month 0xFF and knows the timestamp is unusable.
+        LOG("RTC read failed\n");
+        TIME.Second = TIME.Minute = TIME.Hour = 0xFF;
+        TIME.Wday = TIME.Day = TIME.Month = TIME.Year = 0xFF;
+        return TIME;
+    }
 
-    rtc_read_time_array(DATA_BUFFER_7);
     TIME.Second = BCD2DEC(DATA_BUFFER_7[0]);
     TIME.Minute = BCD2DEC(DATA_BUFFER_7[1]);
     TIME.Hour = BCD2DEC((DATA_BUFFER_7[2] & ~(1 << 6)));