alignment, refresh only if necessary

src/disp.cpp

@@ -57,10 +57,17 @@ void printStringWithWait(char *s, int delayTime, LedControl lc)
     }
 }
 
-void printString(char *s, LedControl lc)
+/**
+ * Careful: manipulates *s!
+ * */
+void printString(char *s, LedControl lc, int offset)
 {
-    int offset = 0;
     int display = 0;
+    
+    for (int i=0;i<lc.getDeviceCount();i++) {
+        lc.clearDisplay(i);
+    }
+
     while (*s != 0)
     {
         if (*s < 32)
@@ -71,7 +78,7 @@ void printString(char *s, LedControl lc)
         {
             if (i+offset>7) {
                 offset = offset-8;
-                display++;
+                display++;                
             }
             lc.setRow(display, i + offset, reverse(buffer[i + 2]));
         }

src/disp.h

@@ -14,7 +14,7 @@ void printStringWithShift(char* s, int delayTime, LedControl lc);
 
 void printStringWithWait(char* s, int delayTime, LedControl lc);
 
-void printString(char* s, LedControl lc);
+void printString(char* s, LedControl lc, int offset);
 
 
 void fadeOut(int max, int time, LedControl lc);
@@ -44,7 +44,7 @@ PROGMEM const unsigned char CH[] = {
 2, 8, B1100000, B1100000, B0000000, B0000000, B0000000, // .
 4, 8, B1100000, B0011000, B0000110, B0000001, B0000000, // /
 4, 8, B0111110, B1000001, B1000001, B0111110, B0000000, // 0
-3, 8, B1000010, B1111111, B1000000, B0000000, B0000000, // 1
+4, 8, B1000010, B1111111, B1000000, B0000000, B0000000, // 1
 4, 8, B1100010, B1010001, B1001001, B1000110, B0000000, // 2
 4, 8, B0100010, B1000001, B1001001, B0110110, B0000000, // 3
 4, 8, B0011000, B0010100, B0010010, B1111111, B0000000, // 4

src/main.cpp

@@ -13,6 +13,8 @@
 #include <FS.h> // Use the SPIFFS library for the filesystem
 #include <LittleFS.h>
 
+#include <time.h> // time() ctime()
+
 #include "disp.h"
 
 /*
@@ -36,6 +38,9 @@ int iteration = 0;
 RTC_DS1307 rtc;
 DateTime now;
 
+time_t tnow; // this is the epoch
+tm stm;      // the structure tm holds time information in a more convient way
+
 #define SCREEN_WIDTH 128 // OLED display width, in pixels
 #define SCREEN_HEIGHT 64 // OLED display height, in pixels
 
@@ -48,13 +53,21 @@ DateTime now;
 #define MAX_CS D6
 #define MAX_DIN D7
 
+/* Configuration of NTP */
+#define MY_NTP_SERVER "de.pool.ntp.org"
+#define MY_TZ "CET-1CEST,M3.5.0/02,M10.5.0/03"
+
 LedControl lc = LedControl(MAX_DIN, MAX_CLK, MAX_CS, 3);
 
 /* we always wait a bit between updates of the display */
-
 unsigned long delaytime = 500;
 
-char str[24];
+unsigned long last_ntp = 0;
+
+#define NTP_INTERVAL 100000
+
+char str[24] = "\0";
+char prev_str[24] = "\0";
 
 void configModeCallback(AsyncWiFiManager *myWiFiManager);
 AsyncWebServer server(80);
@@ -129,6 +142,8 @@ void setup()
     Serial.println("Wifi connected.");
   }
 
+  configTime(MY_TZ, MY_NTP_SERVER); // ntp
+
   //server.on("/", handleRoot);
 
   // Route for root / web page
@@ -179,8 +194,27 @@ void configModeCallback(AsyncWiFiManager *myWiFiManager)
 
 void loop()
 {
+
+  if (millis() - last_ntp > NTP_INTERVAL)
+  {
+    time(&tnow);              // read the current time
+    localtime_r(&tnow, &stm); // update the structure tm with the current time
+    last_ntp = millis();
+    Serial.printf("ntp time: %02d:%02d\n", stm.tm_hour, stm.tm_min);
+    rtc.adjust(DateTime(stm.tm_year, stm.tm_mon, stm.tm_mday, stm.tm_hour, stm.tm_min, stm.tm_sec));
+  }
+
   setTime(str);
-  printString(str, lc);
+  
+  if (strcmp(str,prev_str)!=0) {
+    Serial.printf("%s %s",prev_str,str);
+    strcpy(prev_str, str);
+    printString(str, lc,2);
+  }
+  
+  
+
+  delay(500);
 }
 
 void setTime(char *timeStr)