From 49882b2eb671e01d30defc623319bce43f3ec49a Mon Sep 17 00:00:00 2001
From: Ogneyar <ya13th@mail.ru>
Date: Sat, 31 Aug 2024 14:48:18 +0300
Subject: [PATCH] According to the datasheet, the bits in three registers are
 checked: 0x00, 0x02 and 0x07

---
 libraries/Wire/examples/ds1307/ds1307.ino | 47 ++++++++++++++++++++++-
 1 file changed, 45 insertions(+), 2 deletions(-)

diff --git a/libraries/Wire/examples/ds1307/ds1307.ino b/libraries/Wire/examples/ds1307/ds1307.ino
index cf8bd32..d1ff33a 100644
--- a/libraries/Wire/examples/ds1307/ds1307.ino
+++ b/libraries/Wire/examples/ds1307/ds1307.ino
@@ -19,10 +19,12 @@ void setup()
 
   // Initializing the device as a master on the I2C bus
   Wire.begin();
-  
+
   // Set new time if necessary
-  if (RTC_SET_NEW_TIME)
+  if (RTC_SET_NEW_TIME) {
+    initDS1307(); // Initialization of ds1307
     writeTimeToRtc(); // setting time is written inside the function
+  }
 }
 
 void loop() 
@@ -33,6 +35,47 @@ void loop()
 }
 
 // ------------------- rtc ------------------- //
+// Function for initializing the DS1307 chip
+void initDS1307(void)
+{
+  /* According to the datasheet, the bits in three registers 
+  are checked: 0x00, 0x02 and 0x07
+  */
+  uint8_t oneByte;
+  Wire.requestFrom(RTC_ADDR, 1, 0x00, 1, 1);
+  // Get data
+  if(Wire.available())
+    oneByte = Wire.read();
+  if (oneByte & 0x80) {
+    Wire.beginTransmission(RTC_ADDR); // Start of transaction
+    Wire.write(0x00);                 // Writing command for a transaction
+    Wire.write(oneByte & ~0x80);      // Writing data for a transaction
+    Wire.endTransmission();           // Completing a transaction
+  }
+
+  Wire.requestFrom(RTC_ADDR, 1, 0x02, 1, 1);
+  // Get data
+  if(Wire.available())
+    oneByte = Wire.read();
+  if (oneByte & 0x40) {
+    Wire.beginTransmission(RTC_ADDR); // Start of transaction
+    Wire.write(0x02);                 // Writing command for a transaction
+    Wire.write(oneByte & ~0x40);      // Writing data for a transaction
+    Wire.endTransmission();           // Completing a transaction
+  }
+
+  Wire.requestFrom(RTC_ADDR, 1, 0x07, 1, 1);
+  // Get data
+  if(Wire.available())
+    oneByte = Wire.read();
+  if ((oneByte & 0x03) || !(oneByte & 0x10)) {
+    Wire.beginTransmission(RTC_ADDR);   // Start of transaction
+    Wire.write(0x07);                   // Writing command for a transaction
+    Wire.write(oneByte & ~0x03 | 0x10); // Writing data for a transaction
+    Wire.endTransmission();             // Completing a transaction
+  }
+}
+
 // Function to write new time to rtc
 void writeTimeToRtc(void)
 {