text: 
  ///////////////////////////////////////////////////////////////////////////////
  // \author (c) Marco Paland (info@paland.com)
  //             2014-2018, PALANDesign Hannover, Germany
  //
  // \license The MIT License (MIT)
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  // 
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  // 
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  //
  // \brief Tiny printf, sprintf and (v)snprintf implementation, optimized for speed on
  //        embedded systems with a very limited resources. These routines are thread
  //        safe and reentrant!
  //        Use this instead of the bloated standard/newlib printf cause these use
  //        malloc for printf (and may not be thread safe).
  //
  ///////////////////////////////////////////////////////////////////////////////
  
  #include <stdint.h>
  #include "printf.h"
  
  
  // ntoa conversion buffer size, this must be big enough to hold
  // one converted numeric number including padded zeros (dynamically created on stack)
  // 32 byte is a good default
  #define PRINTF_NTOA_BUFFER_SIZE    32U
  
  // ftoa conversion buffer size, this must be big enough to hold
  // one converted float number including padded zeros (dynamically created on stack)
  // 32 byte is a good default
  #define PRINTF_FTOA_BUFFER_SIZE    32U
  
  // define this to support floating point (%f)
  #define PRINTF_SUPPORT_FLOAT
  
  // define this to support long long types (%llu or %p)
  #define PRINTF_SUPPORT_LONG_LONG
  
  // define this to support the ptrdiff_t type (%t)
  // ptrdiff_t is normally defined in <stddef.h> as long or long long type
  #define PRINTF_SUPPORT_PTRDIFF_T
  
  
  ///////////////////////////////////////////////////////////////////////////////
  
  // internal flag definitions
  #define FLAGS_ZEROPAD   (1U <<  0U)
  #define FLAGS_LEFT      (1U <<  1U)
  #define FLAGS_PLUS      (1U <<  2U)
  #define FLAGS_SPACE     (1U <<  3U)
  #define FLAGS_HASH      (1U <<  4U)
  #define FLAGS_UPPERCASE (1U <<  5U)
  #define FLAGS_CHAR      (1U <<  6U)
  #define FLAGS_SHORT     (1U <<  7U)
  #define FLAGS_LONG      (1U <<  8U)
  #define FLAGS_LONG_LONG (1U <<  9U)
  #define FLAGS_PRECISION (1U << 10U)
  
  typedef unsigned char bool;
  #ifndef false
  #define false 0
  #endif
  #ifndef true
  #define true (!false)
  #endif
  extern void sys_uart_putc(char c);
  static char last_ch;
  void _putchar(char character)
  {
  	if(character == 0x0a && last_ch != 0x0d)
  	{
  		sys_uart_putc(0x0d);
  	}
  	sys_uart_putc(character);
  
  }
  
  // output function type
  typedef void (*out_fct_type)(char character, void* buffer, size_t idx, size_t maxlen);
  
  
  // wrapper (used as buffer) for output function type
  typedef struct {
    void  (*fct)(char character, void* arg);
    void* arg;
  } out_fct_wrap_type;
  
  
  // internal buffer output
  static inline void _out_buffer(char character, void* buffer, size_t idx, size_t maxlen)
  {
    if (idx < maxlen) {
      ((char*)buffer)[idx] = character;
    }
  }
  
  
  // internal null output
  static inline void _out_null(char character, void* buffer, size_t idx, size_t maxlen)
  {
    (void)character; (void)buffer; (void)idx; (void)maxlen;
  }
  
  
  // internal _putchar wrapper
  static inline void _out_char(char character, void* buffer, size_t idx, size_t maxlen)
  {
    (void)buffer; (void)idx; (void)maxlen;
    if (character) {
      _putchar(character);
    }
  }
  
  
  // internal output function wrapper
  static inline void _out_fct(char character, void* buffer, size_t idx, size_t maxlen)
  {
    (void)idx; (void)maxlen;
    // buffer is the output fct pointer
    ((out_fct_wrap_type*)buffer)->fct(character, ((out_fct_wrap_type*)buffer)->arg);
  }
  
  
  // internal strlen
  // \return The length of the string (excluding the terminating 0)
  static inline unsigned int _strlen(const char* str)
  {
    const char* s;
    for (s = str; *s; ++s);
    return (unsigned int)(s - str);
  }
  
  
  // internal test if char is a digit (0-9)
  // \return true if char is a digit
  static inline bool _is_digit(char ch)
  {
    return (ch >= '0') && (ch <= '9');
  }
  
  
  // internal ASCII string to unsigned int conversion
  static unsigned int _atoi(const char** str)
  {
    unsigned int i = 0U;
    while (_is_digit(**str)) {
      i = i * 10U + (unsigned int)(*((*str)++) - '0');
    }
    return i;
  }
  
  
  // internal itoa format
  static size_t _ntoa_format(out_fct_type out, char* buffer, size_t idx, size_t maxlen, char* buf, size_t len, bool negative, unsigned int base, unsigned int prec, unsigned int width, unsigned int flags)
  {
    const size_t start_idx = idx;
  
    // pad leading zeros
    while (!(flags & FLAGS_LEFT) && (len < prec) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
      buf[len++] = '0';
    }
    while (!(flags & FLAGS_LEFT) && (flags & FLAGS_ZEROPAD) && (len < width) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
      buf[len++] = '0';
    }
  
    // handle hash
    if (flags & FLAGS_HASH) {
      if (!(flags & FLAGS_PRECISION) && len && ((len == prec) || (len == width))) {
        len--;
        if (len && (base == 16U)) {
          len--;
        }
      }
      if ((base == 16U) && !(flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
        buf[len++] = 'x';
      }
      else if ((base == 16U) && (flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
        buf[len++] = 'X';
      }
      else if ((base == 2U) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
        buf[len++] = 'b';
      }
      if (len < PRINTF_NTOA_BUFFER_SIZE) {
        buf[len++] = '0';
      }
    }
  
    // handle sign
    if (len && (len == width) && (negative || (flags & FLAGS_PLUS) || (flags & FLAGS_SPACE))) {
      len--;
    }
    if (len < PRINTF_NTOA_BUFFER_SIZE) {
      if (negative) {
        buf[len++] = '-';
      }
      else if (flags & FLAGS_PLUS) {
        buf[len++] = '+';  // ignore the space if the '+' exists
      }
      else if (flags & FLAGS_SPACE) {
        buf[len++] = ' ';
      }
    }
  
    // pad spaces up to given width
    if (!(flags & FLAGS_LEFT) && !(flags & FLAGS_ZEROPAD)) {
      for (size_t i = len; i < width; i++) {
        out(' ', buffer, idx++, maxlen);
      }
    }
  
    // reverse string
    for (size_t i = 0U; i < len; i++) {
      out(buf[len - i - 1U], buffer, idx++, maxlen);
    }
  
    // append pad spaces up to given width
    if (flags & FLAGS_LEFT) {
      while (idx - start_idx < width) {
        out(' ', buffer, idx++, maxlen);
      }
    }
  
    return idx;
  }
  
  
  // internal itoa for 'long' type
  static size_t _ntoa_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long value, bool negative, unsigned long base, unsigned int prec, unsigned int width, unsigned int flags)
  {
    char buf[PRINTF_NTOA_BUFFER_SIZE];
    size_t len = 0U;
  
    // no hash for 0 values
    if (!value) {
      flags &= ~FLAGS_HASH;
    }
  
    // write if precision != 0 and value is != 0
    if (!(flags & FLAGS_PRECISION) || value) {
      do {
        const char digit = (char)(value % base);
        buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10;
        value /= base;
      } while (value && (len < PRINTF_NTOA_BUFFER_SIZE));
    }
  
    return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int)base, prec, width, flags);
  }
  
  
  // internal itoa for 'long long' type
  #if defined(PRINTF_SUPPORT_LONG_LONG)
  static size_t _ntoa_long_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long long value, bool negative, unsigned long long base, unsigned int prec, unsigned int width, unsigned int flags)
  {
    char buf[PRINTF_NTOA_BUFFER_SIZE];
    size_t len = 0U;
  
    // no hash for 0 values
    if (!value) {
      flags &= ~FLAGS_HASH;
    }
  
    // write if precision != 0 and value is != 0
    if (!(flags & FLAGS_PRECISION) || value) {
      do {
        const char digit = (char)(value % base);
        buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10;
        value /= base;
      } while (value && (len < PRINTF_NTOA_BUFFER_SIZE));
    }
  
    return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int)base, prec, width, flags);
  }
  #endif  // PRINTF_SUPPORT_LONG_LONG
  
  
  #if defined(PRINTF_SUPPORT_FLOAT)
  static size_t _ftoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags)
  {
    const size_t start_idx = idx;
  
    char buf[PRINTF_FTOA_BUFFER_SIZE];
    size_t len  = 0U;
    double diff = 0.0;
  
    // if input is larger than thres_max, revert to exponential
    const double thres_max = (double)0x7FFFFFFF;
  
    // powers of 10
    static const double pow10[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000 };
  
    // test for negative
    bool negative = false;
    if (value < 0) {
      negative = true;
      value = 0 - value;
    }
  
    // set default precision to 6, if not set explicitly
    if (!(flags & FLAGS_PRECISION)) {
      prec = 6U;
    }
    // limit precision to 9, cause a prec >= 10 can lead to overflow errors
    while ((len < PRINTF_FTOA_BUFFER_SIZE) && (prec > 9U)) {
      buf[len++] = '0';
      prec--;
    }
  
    int whole = (int)value;
    double tmp = (value - whole) * pow10[prec];
    unsigned long frac = (unsigned long)tmp;
    diff = tmp - frac;
  
    if (diff > 0.5) {
      ++frac;
      // handle rollover, e.g. case 0.99 with prec 1 is 1.0
      if (frac >= pow10[prec]) {
        frac = 0;
        ++whole;
      }
    }
    else if ((diff == 0.5) && ((frac == 0U) || (frac & 1U))) {
      // if halfway, round up if odd, OR if last digit is 0
      ++frac;
    }
  
    // TBD: for very large numbers switch back to native sprintf for exponentials. Anyone want to write code to replace this?
    // Normal printf behavior is to print EVERY whole number digit which can be 100s of characters overflowing your buffers == bad
    if (value > thres_max) {
      return 0U;
    }
  
    if (prec == 0U) {
      diff = value - (double)whole;
      if (diff > 0.5) {
        // greater than 0.5, round up, e.g. 1.6 -> 2
        ++whole;
      }
      else if ((diff == 0.5) && (whole & 1)) {
        // exactly 0.5 and ODD, then round up
        // 1.5 -> 2, but 2.5 -> 2
        ++whole;
      }
    }
    else {
      unsigned int count = prec;
      // now do fractional part, as an unsigned number
      while (len < PRINTF_FTOA_BUFFER_SIZE) {
        --count;
        buf[len++] = (char)(48U + (frac % 10U));
        if (!(frac /= 10U)) {
          break;
        }
      }
      // add extra 0s
      while ((len < PRINTF_FTOA_BUFFER_SIZE) && (count-- > 0U)) {
        buf[len++] = '0';
      }
      if (len < PRINTF_FTOA_BUFFER_SIZE) {
        // add decimal
        buf[len++] = '.';
      }
    }
  
    // do whole part, number is reversed
    while (len < PRINTF_FTOA_BUFFER_SIZE) {
      buf[len++] = (char)(48 + (whole % 10));
      if (!(whole /= 10)) {
        break;
      }
    }
  
    // pad leading zeros
    while (!(flags & FLAGS_LEFT) && (flags & FLAGS_ZEROPAD) && (len < width) && (len < PRINTF_FTOA_BUFFER_SIZE)) {
      buf[len++] = '0';
    }
  
    // handle sign
    if ((len == width) && (negative || (flags & FLAGS_PLUS) || (flags & FLAGS_SPACE))) {
      len--;
    }
    if (len < PRINTF_FTOA_BUFFER_SIZE) {
      if (negative) {
        buf[len++] = '-';
      }
      else if (flags & FLAGS_PLUS) {
        buf[len++] = '+';  // ignore the space if the '+' exists
      }
      else if (flags & FLAGS_SPACE) {
        buf[len++] = ' ';
      }
    }
  
    // pad spaces up to given width
    if (!(flags & FLAGS_LEFT) && !(flags & FLAGS_ZEROPAD)) {
      for (size_t i = len; i < width; i++) {
        out(' ', buffer, idx++, maxlen);
      }
    }
  
    // reverse string
    for (size_t i = 0U; i < len; i++) {
      out(buf[len - i - 1U], buffer, idx++, maxlen);
    }
  
    // append pad spaces up to given width
    if (flags & FLAGS_LEFT) {
      while (idx - start_idx < width) {
        out(' ', buffer, idx++, maxlen);
      }
    }
  
    return idx;
  }
  #endif  // PRINTF_SUPPORT_FLOAT
  
  
  // internal vsnprintf
  static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const char* format, va_list va)
  {
    unsigned int flags, width, precision, n;
    size_t idx = 0U;
  
    if (!buffer) {
      // use null output function
      out = _out_null;
    }
  
    while (*format)
    {
      // format specifier?  %[flags][width][.precision][length]
      if (*format != '%') {
        // no
        out(*format, buffer, idx++, maxlen);
        format++;
        continue;
      }
      else {
        // yes, evaluate it
        format++;
      }
  
      // evaluate flags
      flags = 0U;
      do {
        switch (*format) {
          case '0': flags |= FLAGS_ZEROPAD; format++; n = 1U; break;
          case '-': flags |= FLAGS_LEFT;    format++; n = 1U; break;
          case '+': flags |= FLAGS_PLUS;    format++; n = 1U; break;
          case ' ': flags |= FLAGS_SPACE;   format++; n = 1U; break;
          case '#': flags |= FLAGS_HASH;    format++; n = 1U; break;
          default :                                   n = 0U; break;
        }
      } while (n);
  
      // evaluate width field
      width = 0U;
      if (_is_digit(*format)) {
        width = _atoi(&format);
      }
      else if (*format == '*') {
        const int w = va_arg(va, int);
        if (w < 0) {
          flags |= FLAGS_LEFT;    // reverse padding
          width = (unsigned int)-w;
        }
        else {
          width = (unsigned int)w;
        }
        format++;
      }
  
      // evaluate precision field
      precision = 0U;
      if (*format == '.') {
        flags |= FLAGS_PRECISION;
        format++;
        if (_is_digit(*format)) {
          precision = _atoi(&format);
        }
        else if (*format == '*') {
          const int prec = (int)va_arg(va, int);
          precision = prec > 0 ? (unsigned int)prec : 0U;
          format++;
        }
      }
  
      // evaluate length field
      switch (*format) {
        case 'l' :
          flags |= FLAGS_LONG;
          format++;
          if (*format == 'l') {
            flags |= FLAGS_LONG_LONG;
            format++;
          }
          break;
        case 'h' :
          flags |= FLAGS_SHORT;
          format++;
          if (*format == 'h') {
            flags |= FLAGS_CHAR;
            format++;
          }
          break;
  #if defined(PRINTF_SUPPORT_PTRDIFF_T)
        case 't' :
          flags |= (sizeof(ptrdiff_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
          format++;
          break;
  #endif
        case 'j' :
          flags |= (sizeof(intmax_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
          format++;
          break;
        case 'z' :
          flags |= (sizeof(size_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
          format++;
          break;
        default :
          break;
      }
  
      // evaluate specifier
      switch (*format) {
        case 'd' :
        case 'i' :
        case 'u' :
        case 'x' :
        case 'X' :
        case 'o' :
        case 'b' : {
          // set the base
          unsigned int base;
          if (*format == 'x' || *format == 'X') {
            base = 16U;
          }
          else if (*format == 'o') {
            base =  8U;
          }
          else if (*format == 'b') {
            base =  2U;
          }
          else {
            base = 10U;
            flags &= ~FLAGS_HASH;   // no hash for dec format
          }
          // uppercase
          if (*format == 'X') {
            flags |= FLAGS_UPPERCASE;
          }
  
          // no plus or space flag for u, x, X, o, b
          if ((*format != 'i') && (*format != 'd')) {
            flags &= ~(FLAGS_PLUS | FLAGS_SPACE);
          }
  
          // ignore '0' flag when precision is given
          if (flags & FLAGS_PRECISION) {
            flags &= ~FLAGS_ZEROPAD;
          }
  
          // convert the integer
          if ((*format == 'i') || (*format == 'd')) {
            // signed
            if (flags & FLAGS_LONG_LONG) {
  #if defined(PRINTF_SUPPORT_LONG_LONG)
              const long long value = va_arg(va, long long);
              idx = _ntoa_long_long(out, buffer, idx, maxlen, (unsigned long long)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
  #endif
            }
            else if (flags & FLAGS_LONG) {
              const long value = va_arg(va, long);
              idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
            }
            else {
              const int value = (flags & FLAGS_CHAR) ? (char)va_arg(va, int) : (flags & FLAGS_SHORT) ? (short int)va_arg(va, int) : va_arg(va, int);
              idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned int)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
            }
          }
          else {
            // unsigned
            if (flags & FLAGS_LONG_LONG) {
  #if defined(PRINTF_SUPPORT_LONG_LONG)
              idx = _ntoa_long_long(out, buffer, idx, maxlen, va_arg(va, unsigned long long), false, base, precision, width, flags);
  #endif
            }
            else if (flags & FLAGS_LONG) {
              idx = _ntoa_long(out, buffer, idx, maxlen, va_arg(va, unsigned long), false, base, precision, width, flags);
            }
            else {
              const unsigned int value = (flags & FLAGS_CHAR) ? (unsigned char)va_arg(va, unsigned int) : (flags & FLAGS_SHORT) ? (unsigned short int)va_arg(va, unsigned int) : va_arg(va, unsigned int);
              idx = _ntoa_long(out, buffer, idx, maxlen, value, false, base, precision, width, flags);
            }
          }
          format++;
          break;
        }
  #if defined(PRINTF_SUPPORT_FLOAT)
        case 'f' :
        case 'F' :
          idx = _ftoa(out, buffer, idx, maxlen, va_arg(va, double), precision, width, flags);
          format++;
          break;
  #endif  // PRINTF_SUPPORT_FLOAT
        case 'c' : {
          unsigned int l = 1U;
          // pre padding
          if (!(flags & FLAGS_LEFT)) {
            while (l++ < width) {
              out(' ', buffer, idx++, maxlen);
            }
          }
          // char output
          out((char)va_arg(va, int), buffer, idx++, maxlen);
          // post padding
          if (flags & FLAGS_LEFT) {
            while (l++ < width) {
              out(' ', buffer, idx++, maxlen);
            }
          }
          format++;
          break;
        }
  
        case 's' : {
          char* p = va_arg(va, char*);
          unsigned int l = _strlen(p);
          // pre padding
          if (flags & FLAGS_PRECISION) {
            l = (l < precision ? l : precision);
          }
          if (!(flags & FLAGS_LEFT)) {
            while (l++ < width) {
              out(' ', buffer, idx++, maxlen);
            }
          }
          // string output
          while ((*p != 0) && (!(flags & FLAGS_PRECISION) || precision--)) {
            out(*(p++), buffer, idx++, maxlen);
          }
          // post padding
          if (flags & FLAGS_LEFT) {
            while (l++ < width) {
              out(' ', buffer, idx++, maxlen);
            }
          }
          format++;
          break;
        }
  
        case 'p' : {
          width = sizeof(void*) * 2U;
          flags |= FLAGS_ZEROPAD | FLAGS_UPPERCASE;
  #if defined(PRINTF_SUPPORT_LONG_LONG)
          const bool is_ll = sizeof(uintptr_t) == sizeof(long long);
          if (is_ll) {
            idx = _ntoa_long_long(out, buffer, idx, maxlen, (uintptr_t)va_arg(va, void*), false, 16U, precision, width, flags);
          }
          else {
  #endif
            idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)((uintptr_t)va_arg(va, void*)), false, 16U, precision, width, flags);
  #if defined(PRINTF_SUPPORT_LONG_LONG)
          }
  #endif
          format++;
          break;
        }
  
        case '%' :
          out('%', buffer, idx++, maxlen);
          format++;
          break;
  
        default :
          out(*format, buffer, idx++, maxlen);
          format++;
          break;
      }
    }
  
    // termination
    out((char)0, buffer, idx < maxlen ? idx : maxlen - 1U, maxlen);
  
    // return written chars without terminating \0
    return (int)idx;
  }
  
  
  ///////////////////////////////////////////////////////////////////////////////
  
  
  int lprintf(const char* format, ...)
  {
    va_list va;
    va_start(va, format);
    char buffer[1];
    const int ret = _vsnprintf(_out_char, buffer, (size_t)-1, format, va);
    va_end(va);
    return ret;
  }
  
  
  int sprintf(char* buffer, const char* format, ...)
  {
    va_list va;
    va_start(va, format);
    const int ret = _vsnprintf(_out_buffer, buffer, (size_t)-1, format, va);
    va_end(va);
    return ret;
  }
  
  
  int snprintf(char* buffer, size_t count, const char* format, ...)
  {
    va_list va;
    va_start(va, format);
    const int ret = _vsnprintf(_out_buffer, buffer, count, format, va);
    va_end(va);
    return ret;
  }
  
  
  int vsnprintf(char* buffer, size_t count, const char* format, va_list va)
  {
    return _vsnprintf(_out_buffer, buffer, count, format, va);
  }
  
  
  int fctprintf(void (*out)(char character, void* arg), void* arg, const char* format, ...)
  {
    va_list va;
    va_start(va, format);
    const out_fct_wrap_type out_fct_wrap = { out, arg };
    const int ret = _vsnprintf(_out_fct, (char*)&out_fct_wrap, (size_t)-1, format, va);
    va_end(va);
    return ret;
  }
  