diff -r c7b8a9931b59 -r 2e90ada37476 main/task_sdcard.h
--- a/main/task_sdcard.h	Thu Jul 04 15:57:43 2019 +0200
+++ b/main/task_sdcard.h	Thu Jul 04 21:46:12 2019 +0200
@@ -50,6 +50,17 @@
     char	event[64];		///< Event message.
 } JSON_log;
 
+
+/**
+ * @brief Write application messages to a logfile on the sdcard. The
+ *        logfile is /sdcard/log/sysyyymmdd.log and is only used
+ *        when the time is set from NTP and a card is mounted.
+ *        Log messages are always copied to ESP_LOGI() too.
+ * @param tag is the log tag just as in ESP_LOGx().
+ * @param * is the formatted string.
+ */
+void log_msg(const char *tag, const char *, ...);
+
 /**
  * @brief Begin a new logfile. The logfile is created and written to on
  *        the spiffs filesystem.