From 80ccbaef0dd744dcad1ce7805292be60cb50c143 Mon Sep 17 00:00:00 2001
From: Martin Ayotte <martinayotte@yahoo.ca>
Date: Thu, 6 Aug 2015 13:32:02 -0400
Subject: [PATCH] fix dtostrf() issue using trackerj/odometer fixes along with
 my own fix for string null character ending

---
 cores/esp8266/core_esp8266_noniso.c | 37 ++++++++++++++---------------
 1 file changed, 18 insertions(+), 19 deletions(-)

diff --git a/cores/esp8266/core_esp8266_noniso.c b/cores/esp8266/core_esp8266_noniso.c
index 40fe5e6dd..fecdd3362 100644
--- a/cores/esp8266/core_esp8266_noniso.c
+++ b/cores/esp8266/core_esp8266_noniso.c
@@ -162,46 +162,45 @@ char * dtostrf(double number, signed char width, unsigned char prec, char *s) {
         strcpy(s, "ovf");
         return s;
     }
-
     char* out = s;
-    int signInt_Part = 1;
-
     // Handle negative numbers
     if (number < 0.0) {
-        signInt_Part = -1;
+        *out = '-';
+        ++out;
         number = -number;
     }
 
-    // calc left over digits 
-    if (prec > 0)
-    {
-        width -= (prec + 1);
-    }
-
     // Round correctly so that print(1.999, 2) prints as "2.00"
-    double rounding = 0.5;
+    // I optimized out most of the divisions
+    double rounding = 2.0;
     for (uint8_t i = 0; i < prec; ++i)
-        rounding /= 10.0;
+        rounding *= 10.0;       
+    rounding = 1.0 / rounding;   
 
     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;
-    out += sprintf(out, "%*ld", width, int_part * signInt_Part);
+    out += sprintf(out, "%d", int_part);
 
     // Print the decimal point, but only if there are digits beyond
     if (prec > 0) {
         *out = '.';
         ++out;
-
-
-        for (unsigned char decShift = prec; decShift > 0; decShift--) {
-            remainder *= 10.0;
-        }
-        sprintf(out, "%0*d", prec, (int)remainder);
     }
 
+    // Print the digits after the decimal point
+    int8_t digit = 0;
+    while (prec-- > 0) {
+        remainder *= 10.0;
+        digit = (int8_t)remainder;
+        if (digit > 9) digit = 9; // insurance
+        *out = (char)('0' | digit);
+        ++out;
+        remainder -= digit;
+    }
+    *out = 0;
     return s;
 }