// test program for three cascaded AS1107
// if you got a different configuration you need to
// modify the library itself.

#include <AS1107.h>

// Arduino pins
const byte CsnPin = 2;    // Chip select (Low active)
const byte ClkPin = 3;    // Serial Clock
const byte DataPin = 4;   // Serial Data

byte buffer[24];          // Screen buffer (No. of modules * 8)
AS1107 matrix(CsnPin, ClkPin, DataPin);

const byte d = 0;
int count=1;
void setup()
{
  matrix.Init(buffer);
  matrix.SetScrollText(" Three 8x8 LED dot matrix modules driven by three AS1107 LED controllers using just four I/O pins of the Arduino for serial data. That is surprisingly fast, look:", 1);
}

void loop()
{
  if (matrix.TextScroll()) {
    delay(2000);
    for (int i=0; i<=7; i++) {
      matrix.ShiftUp();
      delay(50);
      matrix.Update();
    }
    for (int i=0; i<=10; i++) {
      CirclePulsate();
    }
    StarsDown();
    for (int i=0; i<=5; i++) {
      Rotator1();
    }
    StarsRight();
    for (int i=0; i<=AS1107::Maxx; i++) {
      matrix.ShiftRight();
      delay(5);
      matrix.Update();
    }
    for (int i=1; i<=3; i++)
    {
      bounce();
    }
  }
  delay(10);
}

void CirclePulsate()
{
  for( int i=0; i<=15; i++) {
    matrix.Clear();
    matrix.DrawEllipse(AS1107::Maxx/2,4,i,i);
    matrix.Update();
    delay(d);
  }
}
void StarsDown()
{
    for( int i=0; i<=200; i++) {
      matrix.ShiftDown();
      matrix.SetLed((byte) random(0,AS1107::Maxx+1),0,1);
      matrix.Update();
      delay(d);
    }
}
void StarsRight()
{
    for( int i=0; i<=200; i++) {
      matrix.ShiftRight();
      matrix.SetLed(0,(byte) random(0,AS1107::Maxy+1),1);
      matrix.Update();
      delay(d);
    }
}
void Rotator1()
{
  for( int i=0; i<=AS1107::Maxx-1; i++) {
    matrix.Clear();
    matrix.DrawLine(i,0,AS1107::Maxx-i,AS1107::Maxy);
    matrix.Update();
    delay(d);
  }
  for( int i=0; i<=6; i++) {
    matrix.Clear();
    matrix.DrawLine(AS1107::Maxx,i,0,7-i);
    matrix.Update();
    delay(d);
  }
}

void bounce()
{
  int rad=0;
  float y=random(0,AS1107::Maxy+1);
  float x=random(0,AS1107::Maxx+1);
  float xacc=random(0,5)-2;
  float yacc=random(0,5)-2;
  float yg=0.08;
  if (xacc == 0) xacc == 1;
  if (yacc == 0) yacc == -1;
  for (int i=1; i<=300; i++)
  {
    x+=xacc;
    y+=yacc;
    yacc += yg;
    if (x >= (AS1107::Maxx-rad)) {
      xacc = -xacc*0.9;
      x= AS1107::Maxx -rad;
    }
    else if (x <= rad) {
      xacc = -xacc*0.8;
      x= rad;
    }
    if (y >= (AS1107::Maxy-rad)) {
      yacc = -(yacc*0.80);
      y= AS1107::Maxy -rad;
    }
    else if (y <= rad) {
      yacc = -yacc*0.8;
      y= rad;
    }
    matrix.Clear();
    matrix.SetLed(x,y,1);
    matrix.Update();
  }
}
 

/*
  AS1107.h - Library for interfacing the AS1107 LED Driver Chip
  Created by Stephan Elsner 2011
  version 0.82

  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 Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

#ifndef AS1107_h
#define AS1107_h

#include "WProgram.h"
#include <avr/pgmspace.h>

#define ON 1
#define OFF 0


// --------------------------------------------------------------------------------------------------------------------------
class AS1107
{
  public:
    AS1107(byte cspin, byte clkpin, byte datapin);
    void WriteRegister2(byte chip, byte reg, byte data);
    void WriteRegister(byte chip, byte reg, byte data);
    void WriteColumn( byte column, byte data);
    void Init(byte *buffer);
    void SetBuffer(byte *buffer);
    void SetLed(int x, int y, byte value);
    void Clear();
    void Update();
    void ShiftLeft();
    void ShiftRight();
    void ShiftUp();
    void ShiftDown();
    void ShiftUp(byte from, byte to);
    void ShiftDown(byte from, byte to);
    void DrawLine(int x0, int y0, int x1, int y1);
    void DrawBox(int x0, int y0, int x1, int y1);
    void DrawEllipse(int xm, int ym, int a, int b);
    void SetScrollText(char *string, int charspacing);
    void DrawText (int x, int y, char *str);
    byte DrawChar (int x, int y, char thechar);

    boolean TextScroll();

    // ***************************************
    // Set your module configuration here
    // ***************************************
    static const byte Maxx=23;      // maximum x - Pixels of the Module
    static const byte Maxy=7;         // maximum y - Pixels of the Module
    static const byte HighestCtrlNum=2; // Number of Matrix modules -1 (0 = single module)

  private:
    byte _cspin;
    byte _clkpin;
    byte _datapin;
    byte *_buffer;                    // pointer to current screen buffer

    static const byte _repcharoff;    // Offset of the replacement for unknown characers
    int  _charoffset[82];             // Start position in Array
    char *_outputstring;              // pointer to start of output string
    char *_curchr;                    // pointer to current char of output String
    int _fontidx;                     // current byte in font to display
    int _colct;                       // to count the columns of character to display
    byte _charspacing;                // the coulumns of space between characters
    boolean _hastext;

    void SetLedInternal(byte x, byte y, byte value);
    boolean NextCharacter();
    void CalculateCharOffsets();
    byte GetInternalCharCode(byte thechar);
};

// --------------------------------------------------------------------------------------------------------------------------
// AS1107-Register
class Registers
{
  public:
    static const byte NoOp   = 0x00;
    static const byte Digit0 = 0x01;
    static const byte Digit1 = 0x02;
    static const byte Digit2 = 0x03;
    static const byte Digit3 = 0x04;
    static const byte Digit4 = 0x05;
    static const byte Digit5 = 0x06;
    static const byte Digit6 = 0x07;
    static const byte Digit7 = 0x08;
    static const byte DecodeMode = 0x09;
    static const byte IntensityControl = 0x0A;
    static const byte ScanLimit = 0x0B;
    static const byte Shutdown = 0x0C;
    static const byte Feature = 0x0E;
    static const byte DisplayTest = 0x0F;
};

// --------------------------------------------------------------------------------------------------------------------------
// Values to write to the Shutdown Register
class ShutdownModes
{
  public:
    static const byte ShutdownResetFeature = 0x00;  // Shutdown Mode, Reset Feature Register to Default Settings
    static const byte Shutdown             = 0x80;  // Shutdown Mode, leaving Feature Register unchanged
    static const byte NormalResetFeature   = 0x01;  // Normal Mode, Reset Feature
    static const byte Normal               = 0x81;  // Normal Mode, Feature unchanged
};

// Bits in the feature-Register, desired Settings must be OR'ed together
class Features
{
  public:
    static const byte ExternalClock        = 0x01;  // ExternalClock active
    static const byte ResetRegisters       = 0x02;  // Resets all control registers except the Feature Register.
    static const byte HexDecoding          = 0x04;  // 1 = Enable HEX decoding, 0 = Enable Code-B decoding
    static const byte SPIEnable            = 0x08;  // Enables the SPI-compatible interface.(AS1106 only).
    static const byte BlinkEnable          = 0x10;  // Enables blinking.
    static const byte BlinkSlow            = 0x20;  // Sets blink with low frequency
                                                    // (with the internal oscillator enabled)

    static const byte BlinkSync            = 0x40;  // Synchronizes blinking on the rising edge of pin LOAD/CSN.
                                                    // The multiplex and blink timing counter is cleared on the
                                                    // rising edge of pin LOAD/CSN. By setting this bit in
                                                    // multiple AS1106/AS1107 devices, the blink timing can
                                                    // be synchronized across all the devices.

    static const byte BlinkStartWithOn     = 0x80;  // Start Blinking with display enabled phase.
                                                    // When bit D4 (blink_en) is set, bit D7
                                                    // determines how blinking starts.
                                                    // 0 = Blinking starts with the display turned off.
                                                    // 1 = Blinking starts with the display turned on.
};

#endif

 

/*
  AS1107.cpp - Library for interfacing the AS1107 LED Driver Chip
  Created by Stephan Elsner, March 29, 2011

  Scrolltext uses a proportional character font
  Tested with Arduino Duemilenove
  version 0.82

  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 Street, Fifth Floor, Boston, MA  02110-1301  USA
*/
#include <avr/pgmspace.h>
#include "WProgram.h"
#include "AS1107.h"

const byte AS1107::_repcharoff  = 27;

// Font Data
PROGMEM prog_uchar _font[] = {
    // -------- Space
    0b00000000,
    0b00000000,
    0b00000000,
    0b00000000,
    // -------- A
    0b01111110,
    0b10010000,
    0b10010000,
    0b01111110,
    // -------- B
    0b01101100,
    0b10010010,
    0b10010010,
    0b11111110,
    // -------- C
    0b10000010,
    0b10000010,
    0b01111100,
    // -------- D
    0b00111000,
    0b01000100,
    0b10000010,
    0b11111110,   
    // -------- E
    0b10000010,   
    0b10010010,   
    0b11111110,
    // -------- F
    0b10000000,       
    0b10010000,       
    0b11111110,
    // -------- G
    0b01011100,     
    0b10010010,
    0b10000010,
    0b01111100,
    // -------- H
    0b11111110,
    0b00010000,
    0b00010000,
    0b11111110,     
    // -------- I
    0b10000010,   
    0b11111110,   
    0b10000010,   
    // -------- J
    0b11111100,     
    0b00000010,
    0b00001100,
    // -------- K
    0b10000110,     
    0b01001000,     
    0b00110000,
    0b11111110,
    // -------- L
    0b00000010,     
    0b00000010,     
    0b11111110,
    // -------- M
    0b11111110,
    0b01100000,
    0b00111100,     
    0b01100000,     
    0b11111110,
    // -------- N
    0b11111110,
    0b00011000,
    0b01100000,     
    0b11111110,     
    // -------- O
    0b01111100,
    0b10000010,
    0b10000010,
    0b01111100,     
    // -------- P
    0b01100000,   
    0b10010000,
    0b10010000,
    0b11111110,
    // -------- Q
    0b01111010,
    0b10000100,
    0b10001010,
    0b01111100,     
    // -------- R
    0b01100110,     
    0b10011000,
    0b10010000,
    0b11111110,
    // -------- S
    0b10001100,
    0b10010010,
    0b01100010,   
    // -------- T
    0b10000000,     
    0b11111110,
    0b10000000,     
    // -------- U
    0b11111100,
    0b00000010,
    0b00000010,
    0b11111100,       
    // -------- V
    0b11000000,
    0b00111000,
    0b00000110,
    0b00111000,
    0b11000000,       
    // -------- W
    0b11111110,
    0b00001100,
    0b00111000,     
    0b00001100,     
    0b11111110,     
    // -------- X
    0b11000110,
    0b00111000,
    0b00111000,     
    0b11000110,
    // -------- Y
    0b11100000,
    0b00011110,
    0b11100000,   
    // -------- Z
    0b11000010,
    0b10110010,
    0b10001110,     
    // -------- Unknown character
    0b00111000,     
    0b00111000,
    0b00111000,
    // -------- 0
    0b01111100,
    0b10100010,
    0b10010010,
    0b01111100,     
    // -------- 1
    0b11111110,
    0b01000000,
    // -------- 2
    0b01100010,
    0b10010010,
    0b10001110,     
    // -------- 3
    0b01101100,
    0b10010010,
    0b10000010,     
    // -------- 4
    0b11111110,
    0b00010000,
    0b11110000,     
    // -------- 5
    0b10001100,
    0b10010010,
    0b11110010,     
    // -------- 6
    0b01001100,
    0b10010010,
    0b10010010,
    0b01111100,     
    // -------- 7
    0b11100000,
    0b10011110,
    0b10000000,     
    // -------- 8
    0b01101100,
    0b10010010,
    0b10010010,
    0b01101100,     
    // -------- 9
    0b01111100,
    0b10010010,
    0b10010010,
    0b01100100,     
    // -------- :
    0b00100100,
    // -------- ;
    0b00100110,
    0b00000001,
    // -------- !
    0b01100000,
    0b11111010,
    0b01100000,
    // -------- Heart
    0b01111000,
    0b11111100,
    0b11111110,
    0b01111111,
    0b11111110,
    0b11111100,
    0b01111000,
    // -------- <
    0b01000100,
    0b00101000,
    0b00010000,
    // -------- =
    0b00101000,
    0b00101000,
    0b00101000,
    0b00101000,
    // -------- >
    0b00010000,
    0b00101000,
    0b01000100,
    // -------- ?
    0b01100000,
    0b10011010,
    0b10000000,
    // -------- @
    0b01111100,
    0b10000010,
    0b10111010,
    0b10100010,
    0b01011100,
    // -------- (
    0b10000010,
    0b01111100,
    // -------- )
    0b01111100,
    0b10000010,
    // -------- *
    0b00101000,
    0b00010000,
    0b00101000,
    // -------- +
    0b00010000,
    0b00010000,
    0b01111100,
    0b00010000,
    0b00010000,
    // -------- ,
    0b00000110,
    0b00000001,   
    // -------- -
    0b00010000,
    0b00010000,
    0b00010000,
    0b00010000,
    // -------- .
    0b00000010,
    // -------- /
    0b11000000,
    0b00111000,
    0b00000110,
    // -------- a
    0b00111110,
    0b00100010,
    0b00100010,
    0b00011100,
    // -------- b
    0b00011100,
    0b00100010,
    0b00100010,
    0b11111110,
    // -------- c
    0b00100010,
    0b00100010,
    0b00011100,
    // -------- d
    0b11111110,
    0b00100010,
    0b00100010,
    0b00011100,
    // -------- e
    0b00011000,
    0b00101010,
    0b00101010,
    0b00011100,
    // -------- f
    0b10010000,
    0b01111110,
    0b00010000,
    // -------- g
    0b00111110,
    0b00100101,
    0b00100101,
    0b00011000,
    // -------- h
    0b00011110,
    0b00100000,
    0b00100000,
    0b11111110,
    // -------- i
    0b00000010,
    0b01011110,
    0b00010010,
    // -------- j
    0b01011110,
    0b00000001,
    0b00000001,
    // -------- k
    0b00100010,
    0b00010100,
    0b00001000,
    0b11111110,
    // -------- l
    0b00000010,
    0b11111100,
    // -------- m
    0b00011110,
    0b00100000,
    0b00111110,
    0b00100000,
    0b00111110,
    // -------- n
    0b00011110,
    0b00100000,
    0b00100000,
    0b00111110,
    // -------- o
    0b00011100,
    0b00100010,
    0b00100010,
    0b00011100,
    // -------- p
    0b00011100,
    0b00100010,
    0b00100010,
    0b00111111,
    // -------- q
    0b00111111,
    0b00100010,
    0b00100010,
    0b00011100,
    // -------- r
    0b00010000,
    0b00100000,
    0b00111110,
    // -------- s
    0b00100100,
    0b00101010,
    0b00101010,
    0b00010010,
    // -------- t
    0b00100010,
    0b11111100,
    0b00100000,
    // -------- u
    0b00111110,
    0b00000010,
    0b00000010,
    0b00111100,
    // -------- v
    0b00111000,
    0b00000110,
    0b00111000,
    // -------- w
    0b00111110,
    0b00000010,
    0b00011110,
    0b00000010,
    0b00111100,
    // -------- x
    0b00110110,
    0b00001000,
    0b00110110,
    // -------- y
    0b00111110,
    0b00000101,
    0b00000101,
    0b00111001,
    // -------- z
    0b00110010,
    0b00101010,
    0b00100110,
    0b00100010,
    0b11000001
};

// Char width table
PROGMEM prog_uchar _charwidth[] = {4,4,4,3,4,3,3,4,4,3,3,4,3,5,4,4,4,4,4,3,3,4,5,5,4,3,3,
                                   3,4,2,3,3,3,3,4,3,4,4,1,2,3,7,3,4,3,3,5,2,2,3,5,2,4,1,3,
                                   4,4,3,4,4,3,4,4,3,3,4,2,5,4,4,4,4,3,4,3,4,3,5,3,4,4,0 };

// ASCII Codes of the implemented characters                                   
PROGMEM prog_uchar _charcodes[] = {32,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,
                           81,82,83,84,85,86,87,88,89,90,255,48,49,50,51,52,53,
                           54,55,56,57,58,59,33,3,60,61,62,63,64,40,41,42,43,44,
                                                   45,46,47,97,98,99,100,101,102,103,104,105,106,107,108,
                                                   109,110,111,112,113,114,115,116,117,118,119,120,121,
                                                   122,0};
// ------------------------------------------------------------------------------------
// Constructor, initialize arduino
AS1107::AS1107(byte cspin, byte clkpin, byte datapin)
{
  _cspin = cspin;
  _clkpin = clkpin;
  _datapin = datapin;
  pinMode(cspin, OUTPUT);
  pinMode(clkpin, OUTPUT);
  pinMode(datapin, OUTPUT);
  digitalWrite(cspin,HIGH);
  digitalWrite(clkpin,LOW);
  digitalWrite(datapin,LOW);
}

// ------------------------------------------------------------------------------------
// Initializes Arduino and AS1107
// buffer is the initial screen buffer
void AS1107::Init(byte * buffer)
{
  _buffer = buffer;
  CalculateCharOffsets();
  // Clear Screen buffer
  Clear();
  for (int i=0; i<=HighestCtrlNum; i++) {
    WriteRegister(i, Registers::Shutdown, ShutdownModes::Normal);
    WriteRegister(i, Registers::DecodeMode, 0x00);
    WriteRegister(i, Registers::IntensityControl, 0x00);
    WriteRegister(i, Registers::ScanLimit, 0x07);
  }
}

// ------------------------------------------------------------------------------------
// Set the Screen buffer
void AS1107::SetBuffer(byte * buffer)
{
  _buffer = buffer;
}

// ------------------------------------------------------------------------------------
// Writes Data to a Register of the AS1106/AS1107
// chip: Number of the controller chip (starting at 0 for the left)
// reg:  Register of the controller
// data: Data to be written
void AS1107::WriteRegister( byte chip, byte reg,  byte data)
{
  if (chip>=0 && chip <= HighestCtrlNum) {
    chip = HighestCtrlNum -chip;
    digitalWrite(_cspin,LOW);
    for (int i=0; i<=HighestCtrlNum; i++) {
    if (i == chip) {
      shiftOut(_datapin, _clkpin, MSBFIRST, reg);
      shiftOut(_datapin, _clkpin, MSBFIRST, data);
    }
    else {
      shiftOut(_datapin, _clkpin, MSBFIRST, Registers::NoOp);
      shiftOut(_datapin, _clkpin, MSBFIRST, 0);
    }
  }
    digitalWrite(_cspin,HIGH);
  }
}

// ------------------------------------------------------------------------------------
// Writes a column of data to the LED-Matrix
// column: column number, starting at 0
// data  : screen data to be written
void AS1107::WriteColumn( byte column,  byte data)
{
  // if you use unusual matrix row wiring, you can manipulate data here
  byte chip = (column) >>3;
  byte reg = (column % 8) +1;
  WriteRegister(chip, reg, data);
}

// ------------------------------------------------------------------------------------
// Sets the status of a LED in the screen buffer
void AS1107::SetLed(int x, int y, byte value)
{
  if (x<=Maxx && y<=Maxy && x>=0 && y>=0) {
    if (value>0) value = 1;
    SetLedInternal(x, y, value);
  }
}

// ------------------------------------------------------------------------------------
// Writes Buffer to Screen
// needs to be called after a graphics operation to see anything
void AS1107::Update()
{
  for (byte i=0; i<=Maxx; i++) {
    WriteColumn(i, _buffer[i]);
  }
}

// ------------------------------------------------------------------------------------
// Clear the Screen Buffer
void AS1107::Clear()
{
  for (byte i=0; i<=Maxx; _buffer[i++]=0);
}

// ------------------------------------------------------------------------------------
// Shift the content of the Screen buffer to the left
void AS1107::ShiftLeft()
{
  for (byte i=1; i<=Maxx; i++) {
    _buffer[i-1] = _buffer[i];
  }
  _buffer[Maxx] = 0;
}
// ------------------------------------------------------------------------------------
// Shift the content of the Screen buffer to the right
void AS1107::ShiftRight()
{
  for (byte i=Maxx; i>=1; i--) {
    _buffer[i] = _buffer[i-1];
  }
  _buffer[0] = 0;
}
// ------------------------------------------------------------------------------------
// Shift the content of the Screen buffer up
void AS1107::ShiftUp()
{
  for (byte i=0; i<=Maxx; i++) {
    _buffer[i] = _buffer[i]<<1 & 0xFE;
  }
}
// ------------------------------------------------------------------------------------
// Shift the content of the Screen buffer up
void AS1107::ShiftUp(byte from, byte to)
{
  for (byte i=from; i<=to; i++) {
    _buffer[i] = _buffer[i]<<1 & 0xFE;
  }
}
// ------------------------------------------------------------------------------------
// Shift the content of the Screen buffer down
void AS1107::ShiftDown()
{
  for (byte i=0; i<=Maxx; i++) {
    _buffer[i] = _buffer[i]>>1 & 0x7F;
  }
}
// ------------------------------------------------------------------------------------
// Shift the content of the Screen buffer down
void AS1107::ShiftDown(byte from, byte to)
{
  for (byte i=from; i<=to; i++) {
    _buffer[i] = _buffer[i]>>1 & 0x7F;
  }
}
// ------------------------------------------------------------------------------------
// draws a line from x0 ,y0 to x1,y1
void AS1107::DrawLine(int x0, int y0, int x1, int y1)
{

  int dx =  abs(x1-x0), sx = x0<x1 ? 1 : -1;
  int dy = -abs(y1-y0), sy = y0<y1 ? 1 : -1;
  int err = dx+dy, e2; /* error value e_xy */

  for(;;){  /* loop */
    SetLed(x0,y0,ON);
    if (x0==x1 && y0==y1) break;
    e2 = 2*err;
    if (e2 >= dy) { err += dy; x0 += sx; } /* e_xy+e_x > 0 */
    if (e2 <= dx) { err += dx; y0 += sy; } /* e_xy+e_y < 0 */
  }
}
// ------------------------------------------------------------------------------------
// draws a box from x0,x0 to x1,y1
void AS1107::DrawBox(int x0, int y0, int x1, int y1)
{
  DrawLine(x0,y0,x1,y0);
  DrawLine(x1,y0,x1,y1);
  DrawLine(x1,y1,x0,y1);
  DrawLine(x0,y1,x0,y0);
}
// ------------------------------------------------------------------------------------
// draws an ellipse
// center xm, ym   - radius a,b
void AS1107::DrawEllipse(int xm, int ym, int a, int b)
{
   if (a ==0 && b== 0) {
  SetLed(xm,ym,ON);
  return;
   }

   int dx = 0, dy = b; /* first quadrant from top left to bottom right */
   int a2 = a*a, b2 = b*b;
   int err = b2-(2*b-1)*a2, e2; /* error value in the first step */

   do {
     SetLed(xm+dx, ym+dy, ON); /* I. Quadrant */
     SetLed(xm-dx, ym+dy, ON); /* II. Quadrant */
     SetLed(xm-dx, ym-dy, ON); /* III. Quadrant */
     SetLed(xm+dx, ym-dy, ON); /* IV. Quadrant */

     e2 = 2*err;
     if (e2 <  (2*dx+1)*b2) { dx++; err += (2*dx+1)*b2; }
     if (e2 > -(2*dy-1)*a2) { dy--; err -= (2*dy-1)*a2; }
   } while (dy >= 0);

   while (dx++ < a) { /* correction for flat ellipses (b=1) */
     SetLed(xm+dx, ym, ON);
     SetLed(xm-dx, ym, ON);
   }
}

// ------------------------------------------------------------------------------------
// Writes Text at a screen position
void AS1107::DrawText (int x, int y, char *str)
{
  byte count;
  char thechar;
  while (*str != '\0') {
    Serial.println(*str,DEC);
    x+=DrawChar(x, y, *str);
    str++;
  }
}

// ------------------------------------------------------------------------------------
// Draws a single character at a screen position
// returns the x-position for the next character
byte AS1107::DrawChar (int x, int y, char thechar)
{
  y+=7;
  byte charnum, colct, count=0, colbits;
  int fontidx;
  charnum = GetInternalCharCode(thechar);

  // get the location of the first column of the font
  fontidx = _charoffset[charnum]-1;

  // get the width of the font
  colct = pgm_read_byte_near(_charwidth + charnum);
  for (byte i=colct; i>0; i--) {
    colbits = pgm_read_byte_near(_font + fontidx + i);
    for (byte j=0; j<=7; j++) {
      if ((colbits >>j) & 1) {
        SetLed(x, y-j, 1);
      }
    }
    x++;
  }
  return colct+1;
}
// ------------------------------------------------------------------------------------
// Sets the Text for Scrolline
void AS1107::SetScrollText(char *string, int charspacing)
{
  _charspacing = charspacing;
  _outputstring = string;
  _curchr = string;
  _hastext = true;
  _colct =-1;
}

// ------------------------------------------------------------------------------------
// Scrolls the text one pixel to the left
// returns true if last character has been displayed
boolean AS1107::TextScroll()
{
  boolean lastchar = false;
  byte colbits = 0;
  if (_colct == (0-_charspacing-1)) {
    lastchar = NextCharacter();
  }
  if (_colct>=0) {
    colbits = pgm_read_byte_near(_font + _fontidx + _colct);
  }
  ShiftLeft();
  _buffer[Maxx] = colbits;
  Update();
  _colct--;
  return lastchar;
}

// ------------------------------------------------------------------------------------
// PRIVATE (Internal) functions
// ------------------------------------------------------------------------------------
// Set LED without Parameter check
void AS1107::SetLedInternal(byte x, byte y, byte value)
{
  _buffer[x] |= value << (Maxy-y);
}

// ------------------------------------------------------------------------------------
// fetches the next character of the Scrollline
// returns true if string is at the end
boolean AS1107::NextCharacter()
{
  boolean lastchar = false;
  if (_hastext) {
    char thechar = *_curchr;
    boolean found = false;
    byte charnum = 0;
    byte i;
    // if the string ends, start from the beginning
    if (thechar == 0) {
      lastchar = true;
      _curchr = _outputstring;
      thechar = *_curchr;
    }

    charnum = GetInternalCharCode(thechar);

    // get the offset of the first column of the character
    _fontidx = _charoffset[charnum];

    // get the width of the font
    _colct = pgm_read_byte_near(_charwidth + charnum) -1;
  }
  else {
    _fontidx= _charoffset[_repcharoff];
    _colct = pgm_read_byte_near(_charwidth + _repcharoff);
  }
  *_curchr++;
  return lastchar;
}
// ------------------------------------------------------------------------------------
// calculates Character offsets from font width table in EEPROM
void AS1107::CalculateCharOffsets()
{
  int off =0;
  int idx=0;
  int w=0;
  int i=0;

  do {
    _charoffset[i]=off;
    w = pgm_read_byte_near(_charwidth+i);
    off += w;
    i++;
  } while (w != 0);
}

// ------------------------------------------------------------------------------------
// gets the character number of the built-in-font from the ASCII table
// returns number of the replacement character for unknown characters
byte AS1107::GetInternalCharCode(byte thechar)
{
    int i=0;
    int charnum;
    do {
      charnum = pgm_read_byte_near(_charcodes + i);
      if (charnum == thechar) break;
      i++;
    } while (charnum != 0 );
    if (charnum == 0) i = _repcharoff;
    return i;
}