diff --git a/src/cores/arduino/Print.cpp b/src/cores/arduino/Print.cpp
index 274ef18..5c1f538 100644
--- a/src/cores/arduino/Print.cpp
+++ b/src/cores/arduino/Print.cpp
@@ -1,46 +1,78 @@
 /*
  Print.cpp - Base class that provides print() and println()
  Copyright (c) 2008 David A. Mellis.  All right reserved.
- 
+
  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.
- 
+
  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.
- 
+
  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
- 
+
  Modified 23 November 2006 by David A. Mellis
- Modified 03 August 2015 by Chuck Todd
+ Modified December 2014 by Ivan Grokhotkov
+ Modified May 2015 by Michael C. Miller - ESP31B progmem support
  */
 
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
-#include <cmath>
+#include <math.h>
+#include <stdarg.h>
 #include "Arduino.h"
 
 #include "Print.h"
-
-using namespace std;
+extern "C" {
+    #include "time.h"
+}
 
 // Public Methods //////////////////////////////////////////////////////////////
 
 /* default implementation: may be overridden */
 size_t Print::write(const uint8_t *buffer, size_t size)
 {
-  size_t n = 0;
-  while (size--) {
-    if (write(*buffer++)) n++;
-    else break;
-  }
-  return n;
+    size_t n = 0;
+    while(size--) {
+        n += write(*buffer++);
+    }
+    return n;
+}
+
+size_t Print::printf(const char *format, ...)
+{
+    char loc_buf[64];
+    char * temp = loc_buf;
+    va_list arg;
+    va_list copy;
+    va_start(arg, format);
+    va_copy(copy, arg);
+    int len = vsnprintf(temp, sizeof(loc_buf), format, copy);
+    va_end(copy);
+    if(len < 0) {
+        va_end(arg);
+        return 0;
+    }
+    if(len >= (int)sizeof(loc_buf)){  // comparation of same sign type for the compiler
+        temp = (char*) malloc(len+1);
+        if(temp == NULL) {
+            va_end(arg);
+            return 0;
+        }
+        len = vsnprintf(temp, len+1, format, arg);
+    }
+    va_end(arg);
+    len = write((uint8_t*)temp, len);
+    if(temp != loc_buf){
+        free(temp);
+    }
+    return len;
 }
 
 size_t Print::print(const __FlashStringHelper *ifsh)
@@ -50,247 +82,294 @@ size_t Print::print(const __FlashStringHelper *ifsh)
 
 size_t Print::print(const String &s)
 {
-  return write(s.c_str(), s.length());
+    return write(s.c_str(), s.length());
 }
 
 size_t Print::print(const char str[])
 {
-  return write(str);
+    return write(str);
 }
 
 size_t Print::print(char c)
 {
-  return write(c);
+    return write(c);
 }
 
 size_t Print::print(unsigned char b, int base)
 {
-  return print((unsigned long) b, base);
+    return print((unsigned long) b, base);
 }
 
 size_t Print::print(int n, int base)
 {
-  return print((long) n, base);
+    return print((long) n, base);
 }
 
 size_t Print::print(unsigned int n, int base)
 {
-  return print((unsigned long) n, base);
+    return print((unsigned long) n, base);
 }
 
 size_t Print::print(long n, int base)
 {
-  if (base == 0) {
-    return write(n);
-  } else if (base == 10) {
-    if (n < 0) {
-      int t = print('-');
-      n = -n;
-      return printNumber(n, 10) + t;
+    int t = 0;
+    if (base == 10 && n < 0) {
+        t = print('-');
+        n = -n;
     }
-    return printNumber(n, 10);
-  } else {
-    return printNumber(n, base);
-  }
+    return printNumber(static_cast<unsigned long>(n), base) + t;
 }
 
 size_t Print::print(unsigned long n, int base)
 {
-  if (base == 0) return write(n);
-  else return printNumber(n, base);
+    if(base == 0) {
+        return write(n);
+    } else {
+        return printNumber(n, base);
+    }
 }
 
 size_t Print::print(long long n, int base)
 {
-  if (base == 0) {
-    return write(n);
-  } else if (base == 10) {
-    if (n < 0) {
-      int t = print('-');
-      n = -n;
-      return printNumber(n, 10) + t;
+    int t = 0;
+    if (base == 10 && n < 0) {
+        t = print('-');
+        n = -n;
     }
-    return printNumber(n, 10);
-  } else {
-    return printNumber(n, base);
-  }
+    return printNumber(static_cast<unsigned long long>(n), base) + t;
 }
 
 size_t Print::print(unsigned long long n, int base)
 {
-  if (base == 0) return write(n);
-  else return printNumber(n, base);
+    if (base == 0) {
+        return write(n);
+    } else {
+        return printNumber(n, base);
+    }
 }
 
 size_t Print::print(double n, int digits)
 {
-  return printFloat(n, digits);
+    return printFloat(n, digits);
 }
 
 size_t Print::println(const __FlashStringHelper *ifsh)
 {
-  size_t n = print(ifsh);
-  n += println();
-  return n;
+    size_t n = print(ifsh);
+    n += println();
+    return n;
 }
 
 size_t Print::print(const Printable& x)
 {
-  return x.printTo(*this);
+    return x.printTo(*this);
+}
+
+size_t Print::print(struct tm * timeinfo, const char * format)
+{
+    const char * f = format;
+    if(!f){
+        f = "%c";
+    }
+    char buf[64];
+    size_t written = strftime(buf, 64, f, timeinfo);
+    if(written == 0){
+        return written;
+    }
+    return print(buf);
 }
 
 size_t Print::println(void)
 {
-  return write("\r\n");
+    return print("\r\n");
 }
 
 size_t Print::println(const String &s)
 {
-  size_t n = print(s);
-  n += println();
-  return n;
+    size_t n = print(s);
+    n += println();
+    return n;
 }
 
 size_t Print::println(const char c[])
 {
-  size_t n = print(c);
-  n += println();
-  return n;
+    size_t n = print(c);
+    n += println();
+    return n;
 }
 
 size_t Print::println(char c)
 {
-  size_t n = print(c);
-  n += println();
-  return n;
+    size_t n = print(c);
+    n += println();
+    return n;
 }
 
 size_t Print::println(unsigned char b, int base)
 {
-  size_t n = print(b, base);
-  n += println();
-  return n;
+    size_t n = print(b, base);
+    n += println();
+    return n;
 }
 
 size_t Print::println(int num, int base)
 {
-  size_t n = print(num, base);
-  n += println();
-  return n;
+    size_t n = print(num, base);
+    n += println();
+    return n;
 }
 
 size_t Print::println(unsigned int num, int base)
 {
-  size_t n = print(num, base);
-  n += println();
-  return n;
+    size_t n = print(num, base);
+    n += println();
+    return n;
 }
 
 size_t Print::println(long num, int base)
 {
-  size_t n = print(num, base);
-  n += println();
-  return n;
+    size_t n = print(num, base);
+    n += println();
+    return n;
 }
 
 size_t Print::println(unsigned long num, int base)
 {
-  size_t n = print(num, base);
-  n += println();
-  return n;
+    size_t n = print(num, base);
+    n += println();
+    return n;
 }
 
 size_t Print::println(long long num, int base)
 {
-  size_t n = print(num, base);
-  n += println();
-  return n;
+    size_t n = print(num, base);
+    n += println();
+    return n;
 }
 
 size_t Print::println(unsigned long long num, int base)
 {
-  size_t n = print(num, base);
-  n += println();
-  return n;
+    size_t n = print(num, base);
+    n += println();
+    return n;
 }
 
 size_t Print::println(double num, int digits)
 {
-  size_t n = print(num, digits);
-  n += println();
-  return n;
+    size_t n = print(num, digits);
+    n += println();
+    return n;
 }
 
 size_t Print::println(const Printable& x)
 {
-  size_t n = print(x);
-  n += println();
-  return n;
+    size_t n = print(x);
+    n += println();
+    return n;
+}
+
+size_t Print::println(struct tm * timeinfo, const char * format)
+{
+    size_t n = print(timeinfo, format);
+    n += println();
+    return n;
 }
 
 // Private Methods /////////////////////////////////////////////////////////////
 
+size_t Print::printNumber(unsigned long n, uint8_t base)
+{
+    char buf[8 * sizeof(n) + 1]; // Assumes 8-bit chars plus zero byte.
+    char *str = &buf[sizeof(buf) - 1];
+
+    *str = '\0';
+
+    // prevent crash if called with base == 1
+    if(base < 2) {
+        base = 10;
+    }
+
+    do {
+        char c = n % base;
+        n /= base;
+
+        *--str = c < 10 ? c + '0' : c + 'A' - 10;
+    } while (n);
+
+    return write(str);
+}
+
 size_t Print::printNumber(unsigned long long n, uint8_t base)
 {
-  char buf[8 * sizeof(long long) + 1]; // Assumes 8-bit chars plus zero byte.
-  char *str = &buf[sizeof(buf) - 1];
-
-  *str = '\0';
-
-  // prevent crash if called with base == 1
-  if (base < 2) base = 10;
-
-  do {
-    char c = n % base;
-    n /= base;
-
-    *--str = c < 10 ? c + '0' : c + 'A' - 10;
-  } while(n);
-
-  return write(str);
-}
-
-size_t Print::printFloat(double number, uint8_t digits) 
-{ 
-  size_t n = 0;
-  
-  if (isnan(number)) return print("nan");
-  if (isinf(number)) return print("inf");
-  if (number > 4294967040.0) return print ("ovf");  // constant determined empirically
-  if (number <-4294967040.0) return print ("ovf");  // constant determined empirically
-  
-  // Handle negative numbers
-  if (number < 0.0)
-  {
-     n += print('-');
-     number = -number;
-  }
-
-  // Round correctly so that print(1.999, 2) prints as "2.00"
-  double rounding = 0.5;
-  for (uint8_t i=0; i<digits; ++i)
-    rounding /= 10.0;
-  
-  number += rounding;
-
-  // Extract the integer part of the number and print it
-  unsigned long int_part = (unsigned long)number;
-  double remainder = number - (double)int_part;
-  n += print(int_part);
-
-  // Print the decimal point, but only if there are digits beyond
-  if (digits > 0) {
-    n += print('.'); 
-  }
-
-  // Extract digits from the remainder one at a time
-  while (digits-- > 0)
-  {
-    remainder *= 10.0;
-    unsigned int toPrint = (unsigned int)(remainder);
-    n += print(toPrint);
-    remainder -= toPrint; 
-  } 
-  
-  return n;
+    char buf[8 * sizeof(n) + 1]; // Assumes 8-bit chars plus zero byte.
+    char* str = &buf[sizeof(buf) - 1];
+
+    *str = '\0';
+
+    // prevent crash if called with base == 1
+    if (base < 2) {
+        base = 10;
+    }
+
+    do {
+        auto m = n;
+        n /= base;
+        char c = m - base * n;
+
+        *--str = c < 10 ? c + '0' : c + 'A' - 10;
+    } while (n);
+
+    return write(str);
+}
+
+size_t Print::printFloat(double number, uint8_t digits)
+{
+    size_t n = 0;
+
+    if(isnan(number)) {
+        return print("nan");
+    }
+    if(isinf(number)) {
+        return print("inf");
+    }
+    if(number > 4294967040.0) {
+        return print("ovf");    // constant determined empirically
+    }
+    if(number < -4294967040.0) {
+        return print("ovf");    // constant determined empirically
+    }
+
+    // Handle negative numbers
+    if(number < 0.0) {
+        n += print('-');
+        number = -number;
+    }
+
+    // Round correctly so that print(1.999, 2) prints as "2.00"
+    double rounding = 0.5;
+    for(uint8_t i = 0; i < digits; ++i) {
+        rounding /= 10.0;
+    }
+
+    number += rounding;
+
+    // Extract the integer part of the number and print it
+    unsigned long int_part = (unsigned long) number;
+    double remainder = number - (double) int_part;
+    n += print(int_part);
+
+    // Print the decimal point, but only if there are digits beyond
+    if(digits > 0) {
+        n += print(".");
+    }
+
+    // Extract digits from the remainder one at a time
+    while(digits-- > 0) {
+        remainder *= 10.0;
+        int toPrint = int(remainder);
+        n += print(toPrint);
+        remainder -= toPrint;
+    }
+
+    return n;
 }
diff --git a/src/cores/arduino/Print.h b/src/cores/arduino/Print.h
index 5c2fa79..57559e5 100644
--- a/src/cores/arduino/Print.h
+++ b/src/cores/arduino/Print.h
@@ -1,27 +1,27 @@
 /*
-  Print.h - Base class that provides print() and println()
-  Copyright (c) 2008 David A. Mellis.  All right reserved.
+ Print.h - Base class that provides print() and println()
+ Copyright (c) 2008 David A. Mellis.  All right reserved.
 
-  This library is free software; you can redistribute it and/or
-  modify it under the terms of the GNU Lesser General Public
-  License as published by the Free Software Foundation; either
-  version 2.1 of the License, or (at your option) any later version.
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
 
-  This library is distributed in the hope that it will be useful,
-  but WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-  Lesser General Public License for more details.
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ Lesser General Public License for more details.
 
-  You should have received a copy of the GNU Lesser General Public
-  License along with this library; if not, write to the Free Software
-  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
-*/
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
 
 #ifndef Print_h
 #define Print_h
 
-#include <inttypes.h>
-#include <stdio.h> // for size_t
+#include <stdint.h>
+#include <stddef.h>
 
 #include "WString.h"
 #include "Printable.h"
@@ -29,38 +29,55 @@
 #define DEC 10
 #define HEX 16
 #define OCT 8
-#ifdef BIN // Prevent warnings if BIN is previously defined in "iotnx4.h" or similar
-#undef BIN
-#endif
 #define BIN 2
 
-//typedef unsigned long long uint64_t;
-//typedef long long int64_t;
-
 class Print
 {
-  private:
+private:
     int write_error;
+    size_t printNumber(unsigned long, uint8_t);
     size_t printNumber(unsigned long long, uint8_t);
     size_t printFloat(double, uint8_t);
-  protected:
-    void setWriteError(int err = 1) { write_error = err; }
-  public:
-    Print() : write_error(0) {}
-  
-    int getWriteError() { return write_error; }
-    void clearWriteError() { setWriteError(0); }
-  
+protected:
+    void setWriteError(int err = 1)
+    {
+        write_error = err;
+    }
+public:
+    Print() :
+        write_error(0)
+    {
+    }
+    virtual ~Print() {}
+    int getWriteError()
+    {
+        return write_error;
+    }
+    void clearWriteError()
+    {
+        setWriteError(0);
+    }
+
     virtual size_t write(uint8_t) = 0;
-    size_t write(const char *str) {
-      if (str == NULL) return 0;
-      return write((const uint8_t *)str, strlen(str));
+    size_t write(const char *str)
+    {
+        if(str == NULL) {
+            return 0;
+        }
+        return write((const uint8_t *) str, strlen(str));
     }
     virtual size_t write(const uint8_t *buffer, size_t size);
-    size_t write(const char *buffer, size_t size) {
-      return write((const uint8_t *)buffer, size);
+    size_t write(const char *buffer, size_t size)
+    {
+        return write((const uint8_t *) buffer, size);
     }
-    
+
+    size_t printf(const char * format, ...)  __attribute__ ((format (printf, 2, 3)));
+
+    // add availableForWrite to make compatible with Arduino Print.h
+    // default to zero, meaning "a single write may block"
+    // should be overriden by subclasses with buffering
+    virtual int availableForWrite() { return 0; }
     size_t print(const __FlashStringHelper *);
     size_t print(const String &);
     size_t print(const char[]);
@@ -70,10 +87,11 @@ class Print
     size_t print(unsigned int, int = DEC);
     size_t print(long, int = DEC);
     size_t print(unsigned long, int = DEC);
-	  size_t print(long long, int = DEC);
+    size_t print(long long, int = DEC);
     size_t print(unsigned long long, int = DEC);
     size_t print(double, int = 2);
     size_t print(const Printable&);
+    size_t print(struct tm * timeinfo, const char * format = NULL);
 
     size_t println(const __FlashStringHelper *);
     size_t println(const String &s);
@@ -84,11 +102,15 @@ class Print
     size_t println(unsigned int, int = DEC);
     size_t println(long, int = DEC);
     size_t println(unsigned long, int = DEC);
-	  size_t println(long long, int = DEC);
+    size_t println(long long, int = DEC);
     size_t println(unsigned long long, int = DEC);
     size_t println(double, int = 2);
     size_t println(const Printable&);
+    size_t println(struct tm * timeinfo, const char * format = NULL);
     size_t println(void);
+    
+    virtual void flush() { /* Empty implementation for backward compatibility */ }
+    
 };
 
 #endif
diff --git a/src/cores/arduino/Printable.h b/src/cores/arduino/Printable.h
index 2a1b2e9..eec5078 100644
--- a/src/cores/arduino/Printable.h
+++ b/src/cores/arduino/Printable.h
@@ -1,40 +1,40 @@
-/*
-  Printable.h - Interface class that allows printing of complex types
-  Copyright (c) 2011 Adrian McEwen.  All right reserved.
-
-  This library is free software; you can redistribute it and/or
-  modify it under the terms of the GNU Lesser General Public
-  License as published by the Free Software Foundation; either
-  version 2.1 of the License, or (at your option) any later version.
-
-  This library is distributed in the hope that it will be useful,
-  but WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-  Lesser General Public License for more details.
-
-  You should have received a copy of the GNU Lesser General Public
-  License along with this library; if not, write to the Free Software
-  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
-*/
-
-#ifndef Printable_h
-#define Printable_h
-
-#include <stdlib.h>
-
-class Print;
-
-/** The Printable class provides a way for new classes to allow themselves to be printed.
-    By deriving from Printable and implementing the printTo method, it will then be possible
-    for users to print out instances of this class by passing them into the usual
-    Print::print and Print::println methods.
-*/
-
-class Printable
-{
-  public:
-    virtual size_t printTo(Print& p) const = 0;
-};
-
-#endif
-
+/*
+  Printable.h - Interface class that allows printing of complex types
+  Copyright (c) 2011 Adrian McEwen.  All right reserved.
+
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Lesser General Public
+  License as published by the Free Software Foundation; either
+  version 2.1 of the License, or (at your option) any later version.
+
+  This library is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with this library; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#ifndef Printable_h
+#define Printable_h
+
+#include <stdlib.h>
+
+class Print;
+
+/** The Printable class provides a way for new classes to allow themselves to be printed.
+    By deriving from Printable and implementing the printTo method, it will then be possible
+    for users to print out instances of this class by passing them into the usual
+    Print::print and Print::println methods.
+*/
+
+class Printable
+{
+  public:
+    virtual size_t printTo(Print& p) const = 0;
+};
+
+#endif
+