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// Code to copy a MCM font file to the Arduino + Max7456 OSD

//

// MAX7456_font Sketch

// at 9600 baud it take about 3min to download a mcm file

// http://www.maxim-ic.com/tools/evkit/index.cfm?EVKit=558

// max7456 evaluation kit software

#define DATAOUT 11//11-MOSI

#define DATAIN  12//12-MISO

#define SPICLOCK  13//13-sck

#define MAX7456SELECT 6 //6

#define USBSELECT 10//10-ss

#define VSYNC 2// INT0

//MAX7456 opcodes

#define VM0_reg   0x00

#define VM1_reg   0x01

#define DMM_reg   0x04

#define DMAH_reg  0x05

#define DMAL_reg  0x06

#define DMDI_reg  0x07

#define CMM_reg   0x08

#define CMAH_reg  0x09

#define CMAL_reg  0x0A

#define CMDI_reg  0x0B

#define STAT_reg  0xA0

//MAX7456 commands

#define CLEAR_display 0x04

#define CLEAR_display_vert 0x06

#define END_string 0xff

#define WRITE_nvr 0xa0

// with NTSC

#define ENABLE_display 0x08

#define ENABLE_display_vert 0x0c

#define MAX7456_reset 0x02

#define DISABLE_display 0x00

// with PAL

// all VM0_reg commands need bit 6 set

//#define ENABLE_display 0x48

//#define ENABLE_display_vert 0x4c

//#define MAX7456_reset 0x42

//#define DISABLE_display 0x40

#define WHITE_level_80 0x03

#define WHITE_level_90 0x02

#define WHITE_level_100 0x01

#define WHITE_level_120 0x00

#define MAX_font_rom 0xff

#define STATUS_reg_nvr_busy 0x20

#define NVM_ram_size 0x36

// with NTSC

#define MAX_screen_rows 0x0d //13

// with PAL

//#define MAX_screen_rows 0x10 //16

volatile byte screen_buffer[MAX_font_rom];

volatile byte character_bitmap[0x40];

volatile byte ascii_binary[0x08];

volatile byte bit_count;

volatile byte byte_count;

volatile int font_count;

volatile int  incomingByte;

volatile int  count;

//////////////////////////////////////////////////////////////

void setup()

{

  byte spi_junk;

  int x;

  Serial.begin(38400);

  Serial.flush();

  digitalWrite(USBSELECT,HIGH); //disable USB chip

  pinMode(MAX7456SELECT,OUTPUT);

  digitalWrite(MAX7456SELECT,HIGH); //disable device

  pinMode(DATAOUT, OUTPUT);

  pinMode(DATAIN, INPUT);

  pinMode(SPICLOCK,OUTPUT);

  pinMode(VSYNC, INPUT);

  // SPCR = 01010000

  //interrupt disabled,spi enabled,msb 1st,master,clk low when idle,

  //sample on leading edge of clk,system clock/4 rate (4 meg)

  SPCR = (1<<SPE)|(1<<MSTR);

  spi_junk=SPSR;

  spi_junk=SPDR;

  delay(250);

  // force soft reset on Max7456

  digitalWrite(MAX7456SELECT,LOW);

  spi_transfer(VM0_reg);

  spi_transfer(MAX7456_reset);

  digitalWrite(MAX7456SELECT,HIGH);

  delay(500);

  // set all rows to same character white level, 90%

  digitalWrite(MAX7456SELECT,LOW);

  for (x = 0; x < MAX_screen_rows; x++)

  {

    spi_transfer(x + 0x10);

    spi_transfer(WHITE_level_90);

  }

  // make sure the Max7456 is enabled

  spi_transfer(VM0_reg);

  spi_transfer(ENABLE_display);

  digitalWrite(MAX7456SELECT,HIGH);

  incomingByte = 0;

  count = 0;

  bit_count = 0;

  byte_count = 0;

  font_count = 0;

  //display all 256 internal MAX7456 characters

  for (x = 0; x < MAX_font_rom; x++)

  {

    screen_buffer[x] = x;

  }

   count = MAX_font_rom;

   write_new_screen();

  Serial.println("Ready for text file download");

  Serial.println("");

  delay(100);

}

//////////////////////////////////////////////////////////////

void loop()

{

  byte x;

  if (Serial.available() > 0)

  {

    // read the incoming byte:

    incomingByte = Serial.read();

    switch(incomingByte) // parse and decode mcm file

    {

      case 0x0d: // carridge return, end of line

        //Serial.println("cr");

       if (bit_count == 8 && (ascii_binary[0] == 0x30 || ascii_binary[0] == 0x31))

       {

          // turn 8 ascii binary bytes to single byte '01010101' = 0x55

          // fill in 64 bytes of character data

         character_bitmap[byte_count] = decode_ascii_binary();

         byte_count++;

         bit_count = 0;

       }

       else

         bit_count = 0;

      break;

      case 0x0a: // line feed, ignore

        //Serial.println("ln");

      break;

      case 0x30: // ascii '0'

      case 0x31: // ascii '1'

        ascii_binary[bit_count] = incomingByte;

        bit_count++;

      break;

      default:

      break;

    }

  }

  // we have one completed character

  // write the character to NVM

  if(byte_count == 64)

  {

    write_NVM();

    byte_count = 0;

    font_count++;

  }

  // we have burned all 256 characters in NVM

  if(font_count == 256)

  {

    font_count = 0;

    // force soft reset on Max7456

    digitalWrite(MAX7456SELECT,LOW);

    spi_transfer(VM0_reg);

    spi_transfer(MAX7456_reset);

    digitalWrite(MAX7456SELECT,HIGH);

    delay(500);

   // display all 256 new internal MAX7456 characters

   for (x = 0; x < MAX_font_rom; x++)

   {

      screen_buffer[x] = x;

   }

    count = MAX_font_rom;

    write_new_screen();

    Serial.println("");

    Serial.println("Done with file download");

  }

}

//////////////////////////////////////////////////////////////

byte spi_transfer(volatile byte data)

{

  SPDR = data;                    // Start the transmission

  while (!(SPSR & (1<<SPIF)))     // Wait the end of the transmission

  {

  };

  return SPDR;                    // return the received byte

}

//////////////////////////////////////////////////////////////

void write_new_screen()

{

  int x, local_count;

  byte char_address_hi, char_address_lo;

  byte screen_char;

  local_count = count;

  char_address_hi = 0;

  char_address_lo = 60; // start on third line

 //Serial.println("write_new_screen");

  // clear the screen

  digitalWrite(MAX7456SELECT,LOW);

  spi_transfer(DMM_reg);

  spi_transfer(CLEAR_display);

  digitalWrite(MAX7456SELECT,HIGH);

  // disable display

  digitalWrite(MAX7456SELECT,LOW);

  spi_transfer(VM0_reg);

  spi_transfer(DISABLE_display);

  spi_transfer(DMM_reg); //dmm

  //spi_transfer(0x21); //16 bit trans background

  spi_transfer(0x01); //16 bit trans w/o background

  spi_transfer(DMAH_reg); // set start address high

  spi_transfer(char_address_hi);

  spi_transfer(DMAL_reg); // set start address low

  spi_transfer(char_address_lo);

  x = 0;

  while(local_count) // write out full screen

  {

    screen_char = screen_buffer[x];

    spi_transfer(DMDI_reg);

    spi_transfer(screen_char);

    x++;

    local_count--;

  }

  spi_transfer(DMDI_reg);

  spi_transfer(END_string);

  spi_transfer(VM0_reg); // turn on screen next vertical

  spi_transfer(ENABLE_display_vert);

  digitalWrite(MAX7456SELECT,HIGH);

}

//////////////////////////////////////////////////////////////

byte decode_ascii_binary()

{

  byte ascii_byte;

  ascii_byte = 0;

  if (ascii_binary[0] == 0x31) // ascii '1'

    ascii_byte = ascii_byte + 128;

  if (ascii_binary[1] == 0x31)

    ascii_byte = ascii_byte + 64;

  if (ascii_binary[2] == 0x31)

    ascii_byte = ascii_byte + 32;

  if (ascii_binary[3] == 0x31)

    ascii_byte = ascii_byte + 16;

  if (ascii_binary[4] == 0x31)

    ascii_byte = ascii_byte + 8;

  if (ascii_binary[5] == 0x31)

    ascii_byte = ascii_byte + 4;

  if (ascii_binary[6] == 0x31)

    ascii_byte = ascii_byte + 2;

  if (ascii_binary[7] == 0x31)

    ascii_byte = ascii_byte + 1;

  //Serial.print(ascii_byte, HEX);

  return(ascii_byte);

}

//////////////////////////////////////////////////////////////

void write_NVM()

{

  byte x;

  byte char_address_hi, char_address_lo;

  byte screen_char;

  char_address_hi = font_count;

  char_address_lo = 0;

 //Serial.println("write_new_screen");

  // disable display

  digitalWrite(MAX7456SELECT,LOW);

  spi_transfer(VM0_reg);

  spi_transfer(DISABLE_display);

  spi_transfer(CMAH_reg); // set start address high

  spi_transfer(char_address_hi);

  for(x = 0; x < NVM_ram_size; x++) // write out 54 (out of 64) bytes of character to shadow ram

  {

    screen_char = character_bitmap[x];

    spi_transfer(CMAL_reg); // set start address low

    spi_transfer(x);

    spi_transfer(CMDI_reg);

    spi_transfer(screen_char);

  }

  // transfer a 54 bytes from shadow ram to NVM

  spi_transfer(CMM_reg);

  spi_transfer(WRITE_nvr);

  // wait until bit 5 in the status register returns to 0 (12ms)

  while ((spi_transfer(STAT_reg) & STATUS_reg_nvr_busy) != 0x00);

  spi_transfer(VM0_reg); // turn on screen next vertical

  spi_transfer(ENABLE_display_vert);

  digitalWrite(MAX7456SELECT,HIGH);

}