From df757206a45b1162e281fa902a0d959287f2aa06 Mon Sep 17 00:00:00 2001
From: Ladyada <limor@ladyada.net>
Date: Thu, 9 Aug 2012 10:25:45 -0400
Subject: [PATCH] Float/Double neg # fixes by John Archie

---
 Adafruit_LEDBackpack.cpp | 164 +++++++++++++++------------------------
 Adafruit_LEDBackpack.h   |   9 ++-
 2 files changed, 69 insertions(+), 104 deletions(-)

diff --git a/Adafruit_LEDBackpack.cpp b/Adafruit_LEDBackpack.cpp
index 4c3c650..d85eed5 100644
--- a/Adafruit_LEDBackpack.cpp
+++ b/Adafruit_LEDBackpack.cpp
@@ -23,19 +23,16 @@
 #include "Adafruit_GFX.h"
 
 static const uint8_t numbertable[] = { 
-	0x3F /* 0 */, 
-	0x06 /* 1 */,
-	0x5B /* 2 */,
-	0x4F /* 3 */,
-	0x66 /* 4 */,
-	0x6D /* 5 */,
+	0x3F, /* 0 */
+	0x06, /* 1 */
+	0x5B, /* 2 */
+	0x4F, /* 3 */
+	0x66, /* 4 */
+	0x6D, /* 5 */
 	0x7D, /* 6 */
 	0x07, /* 7 */
 	0x7F, /* 8 */
 	0x6F, /* 9 */
-};
-
-const uint8_t alphatable[] = {
 	0x77, /* a */
 	0x7C, /* b */
 	0x39, /* C */
@@ -275,108 +272,73 @@ void Adafruit_7segment::writeDigitNum(uint8_t d, uint8_t num, boolean dot) {
   writeDigitRaw(d, numbertable[num] | (dot << 7));
 }
 
-void Adafruit_7segment::writeDigitAlpha(uint8_t d, uint8_t alph, boolean dot) {
-  if (d > 4) return;
-
-  writeDigitRaw(d, alphatable[alph] | (dot << 7));
-}
-
 void Adafruit_7segment::print(long n, int base)
 {
-  if (base == 0) {
-    write(n);
-  } else if (base == 10) {
-    if (n < 0) {
-      print('-');
-      n = -n;
-    }
-    printNumber(n, 10);
-  } else {
-    printNumber(n, base);
-  }
+  printNumber(n, base);
 }
 
-
-void Adafruit_7segment::printNumber(unsigned long n, uint8_t base)
+void Adafruit_7segment::printNumber(long n, uint8_t base)
 {
-  position = 0;
+    printFloat(n, 0, base);
+}
 
-  unsigned char buf[8 * sizeof(long)]; // Assumes 8-bit chars. 
-  unsigned long i = 0;
-
-  if (n == 0) {
-    writeDigitRaw(0, 0x0);
-    writeDigitRaw(1, 0x0);
-    writeDigitRaw(2, 0x0);
-    writeDigitRaw(3, 0x0);
-    writeDigitNum(4, 0);
-    return;
-  } 
-
-  while (n > 0) {
-    buf[i++] = n % base;
-    n /= base;
+void Adafruit_7segment::printFloat(double n, uint8_t fracDigits, uint8_t base) 
+{ 
+  uint8_t numericDigits = 4;   // available digits on display
+  boolean isNegative = false;  // true if the number is negative
+  
+  // is the number negative?
+  if(n < 0) {
+    isNegative = true;  // need to draw sign later
+    --numericDigits;    // the sign will take up one digit
+    n *= -1;            // pretend the number is positive
   }
-
-  // we have i digits
-
-  if (i > 4) { // too big!
-    Serial.println("too long");
-    writeDigitRaw(0, 0x40);
-    writeDigitRaw(1, 0x40);
-    writeDigitRaw(2, 0x00);
-    writeDigitRaw(3, 0x40);
-    writeDigitRaw(4, 0x40);
-    return;
+  
+  // calculate the factor required to shift all fractional digits
+  // into the integer part of the number
+  double toIntFactor = 1.0;
+  for(int i = 0; i < fracDigits; ++i) toIntFactor *= base;
+  
+  // create integer containing digits to display by applying
+  // shifting factor and rounding adjustment
+  uint32_t displayNumber = n * toIntFactor + 0.5;
+  
+  // calculate upper bound on displayNumber given
+  // available digits on display
+  uint32_t tooBig = 1;
+  for(int i = 0; i < numericDigits; ++i) tooBig *= base;
+  
+  // if displayNumber is too large, try fewer fractional digits
+  while(displayNumber >= tooBig) {
+    --fracDigits;
+    toIntFactor /= base;
+    displayNumber = n * toIntFactor + 0.5;
   }
-  //Serial.println(i);
-
-  clear();
-
-  position = 4;
-  for (uint8_t n=0; n<i; n++) {
-    if (buf[n] < 10)
-      writeDigitNum(position, buf[n]);
-    else 
-      writeDigitAlpha(position,  buf[n] - 10);
-
-    position--;
-    if (position == 2) position--;
+  
+  // did toIntFactor shift the decimal off the display?
+  if (toIntFactor < 1) {
+    printError();
+  } else {
+    // otherwise, display the number
+    int8_t displayPos = 4;
+    
+    for(uint8_t i = 0; displayNumber; ++i) {
+      boolean displayDecimal = (fracDigits != 0 && i == fracDigits);
+      writeDigitNum(displayPos--, displayNumber % base, displayDecimal);
+      if(displayPos == 2) writeDigitRaw(displayPos--, 0x00);
+      displayNumber /= base;
+    }
+  
+    // display negative sign if negative
+    if(isNegative) writeDigitRaw(displayPos--, 0x40);
+  
+    // clear remaining display positions
+    while(displayPos >= 0) writeDigitRaw(displayPos--, 0x00);
   }
-  position = 0;
 }
 
-void Adafruit_7segment::printFloat(double number, uint8_t digits) 
-{ 
-  // Handle negative numbers
-  if (number < 0.0)
-  {
-     print('-');
-     number = -number;
+void Adafruit_7segment::printError(void) {
+  for(uint8_t i = 0; i < SEVENSEG_DIGITS; ++i) {
+    writeDigitRaw(i, (i == 2 ? 0x00 : 0x40));
   }
-
-  // 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;
-  print(int_part);
-
-  // Print the decimal point, but only if there are digits beyond
-  if (digits > 0)
-    print('.'); 
-
-  // Extract digits from the remainder one at a time
-  while (digits-- > 0)
-  {
-    remainder *= 10.0;
-    int toPrint = int(remainder);
-    print(toPrint);
-    remainder -= toPrint; 
-  } 
 }
diff --git a/Adafruit_LEDBackpack.h b/Adafruit_LEDBackpack.h
index 3c1da25..87bd3d2 100644
--- a/Adafruit_LEDBackpack.h
+++ b/Adafruit_LEDBackpack.h
@@ -45,6 +45,9 @@
 
 #define HT16K33_CMD_BRIGHTNESS 0x0E
 
+#define SEVENSEG_DIGITS 5
+
+
 // this is the raw HT16K33 controller
 class Adafruit_LEDBackpack {
  public:
@@ -110,10 +113,10 @@ class Adafruit_7segment : public Adafruit_LEDBackpack {
   
   void writeDigitRaw(uint8_t x, uint8_t bitmask);
   void writeDigitNum(uint8_t x, uint8_t num, boolean dot = false);
-  void writeDigitAlpha(uint8_t x, uint8_t num, boolean dot = false);
   void drawColon(boolean state);
-  void printNumber(unsigned long n, uint8_t base);
-  void printFloat(double number, uint8_t digits);
+  void printNumber(long, uint8_t = 2);
+  void printFloat(double, uint8_t = 2, uint8_t = DEC);
+  void printError(void);
 
  private:
   uint8_t position;