How To use the SPI and LCD driver

Configuration of SPI

The LCD can receive serial data via SPI interface, but this has to be first configured :

//----------------------------------------------------

// SPI Configuration pour DAC ou LCD

//----------------------------------------------------

#define SPI_Config()  \

{ \

/* SPI initialization pour DSP-> DAC ou LCD (clk pol 1, no clkphase, master, no INT)*/ \

  SPICCR=0xC7;        /* Reset SPI by writing 1 to SWRST !!!clk pol1                */ \

  SPICTL=0x04;        /* Disable ints & TALK, normal clock, master mode clk phase 0 */ \

  SPIPRI=0x00;        /* Set SPI interrupt to high priority.                        */ \

  SPIBRR=0x00;        /* Baudrate = Fatest as possible ! SYSCLK/4 et ça marche !    */ \

  SPISTS=0x00;        /* Clear the SPI interrupt status bits                        */ \

  SPICTL=0x06;        /* Enable TALK, CLK ph 0, master mode + disable SPI Int    */ \

  SPIPC1=0x52;        /* Enable the SPICLK pin function. ; SPISTE as output pin et mise à 1 ie desactive  */ \

  SPIPC2=0x22;        /* Set SIMO & SOMI functions to serial I/O                    */ \

  SPICCR=0x47;     /* Release SWRST, clock polarity 1, 8 bits          */ \

}

Then you must :

Initialise the LCD screen
Send the data, periodically if you want to display variables changes or so...

LCD driver initialisation sequence

We must clear the LCD screen and configure correctly

//----------------------------------------------------

// initialisation de l'écran LCD

//----------------------------------------------------

inline void LCD_initScreen()

{

      DispLCDOrder( 0xC0, 0x00);      // foncé

      Attends(1000);

      DispLCDOrder( 0x00, 0x80);      // clear LCD, 1.53 ms

      Attends(1000);

      DispLCDOrder( 0x00, 0x60);          // increment, 1.53 ms

      Attends(1000);

      DispLCDOrder( 0x00, 0x30);          // display on, cursor Off

      Attends(30);

//debug si on veut afficher 2 caracteres

//      DispLCDChar( 0x20, 0x80);    // A

//      Attends(30);

//      DispLCDChar( 0x20, 0x40);    // B

//      Attends(30);

      LCDupdate=1;      // doit MAJ la table sur l'Ecran LCD

      LCDline=0;      // REW au début de la table

      LCDcol=0;

}

Communication diagram

We must send 3 bytes on the SPI in the following sequence.

DispLCD function description

We have 2 inline functions to sends 3 bytes on the SPI.
DispLCDChar sends characters corresponding to the Char Table (see below).
DispLCDOrder sends orders like configuration modification (clear screen, cursor home...).

//----------------------------------------------------

// Envoi 3 bytes au LCD : char  requiert hi et low 

//----------------------------------------------------

inline void DispLCDChar(int hi, int low)

{

  CS_LCDon      // Active le LCD via le /CS

  SPIBUF=SPIBUF;          // clear le SPISTS,BIT6

  SPIDAT=0xFA;  // Transmit start Char Order

  while (! (SPISTS & SETB6)) {}

  SPIBUF=SPIBUF;      // clear le SPISTS,BIT6 : donnée_envoyé

  SPIDAT=low;

  while (! (SPISTS & SETB6)) {}

  SPIBUF=SPIBUF;      // clear le SPISTS,BIT6 : donnée_envoyé

  SPIDAT=hi;

  while (! (SPISTS & SETB6)) {}

  SPIBUF=SPIBUF;      // clear le SPISTS,BIT6 : donnée_envoyé

  CS_LCDoff

}

//----------------------------------------------------

// Envoi 3 bytes au LCD : ordre  requiert hi et low 

//----------------------------------------------------

inline void DispLCDOrder(int hi, int low)

{

  CS_LCDon      // Active le LCD via le /CS

  SPIBUF=SPIBUF;          // clear le SPISTS,BIT6

  SPIDAT=0xF8;  // Transmit start Ordre

  while (! (SPISTS & SETB6)) {}

  SPIBUF=SPIBUF;      // clear le SPISTS,BIT6 : donnée_envoyé

  SPIDAT=low;

  while (! (SPISTS & SETB6)) {}

  SPIBUF=SPIBUF;      // clear le SPISTS,BIT6 : donnée_envoyé

  SPIDAT=hi;

  while (! (SPISTS & SETB6)) {}

  SPIBUF=SPIBUF;      // clear le SPISTS,BIT6 : donnée_envoyé

  CS_LCDoff

}

According to the previous graph, the bits order is D0 to D7, but the SPI send the Hi bit first (MSB) (ie. from D7 to D0). So you have to implement a routine or macro, let's call it trChar (see below).

Char Table

trChar function description

This inline function inverts the byte to be sent. Form D0 through D7, it becomes D7 through D0.
Then it creates two bytes : LCDlo and LCDhi, that have only half of them that is non zero, according to the communication diagram.

//----------------------------------------------------

// Routine trChar : transforme le char LCDChar en LCDChar_m (pour le LCD)

//----------------------------------------------------

inline void trChar()

{

  LCDChar_m=0x00;

  for (tmp=8; tmp>0; tmp--)

    {

    LCDChar_m=LCDChar_m<<1 | (LCDChar & 1);

    LCDChar=LCDChar>>1;

    }

  LCDlo=LCDChar_m & 0xF0;

  LCDhi=LCDChar_m<<4 & 0xF0;

}

ConvHexa function description

This inline function converts from an Hexa word to 4 ASCII chars and put them in the buffer LCDtable.

//----------------------------------------------------

// Convertit un "Word" hexa en "4 chars Hexadécimaux"

// et les sort sur la table en memoire

//----------------------------------------------------

inline void ConvHexa(int Var, int LCDtablePos)

{  

      tmp=Var & 0x000F;

      if (tmp<=9)  tmp+=0x30;

          else      tmp+=0x37;

      LCDtable[LCDtablePos+3]=tmp;

      tmp=Var>>4 & 0x000F;

      if (tmp<=9)  tmp+=0x30;

          else      tmp+=0x37;

      LCDtable[LCDtablePos+2]=tmp;

      tmp=Var>>8 & 0x000F;

      if (tmp<=9)  tmp+=0x30;

          else      tmp+=0x37;

      LCDtable[LCDtablePos+1]=tmp;

      tmp=Var>>12 & 0x000F;

      if (tmp<=9)  tmp+=0x30;

          else      tmp+=0x37;

      LCDtable[LCDtablePos]=tmp;

}

LCD instruction Table

This table is extracted from the full SAMSUNG KS0074 pdf driver file or from the SELTRONIC LCD pdf file : Instructions.pdf

Refresh the screen

An intersting use of this LCD screen is to display internal variables of the F240 program that is real time running.
According to an interrupt, let say every 100 us, we could write one character at a time.
So you can implement a table (2x16 characters) in memory where you write variables in Hex or Decimal (look at the page : Hex to Decimal conversion).

Every sampling period, you will check if you have to refresh the LCD screen and write 1 characters from the table to the LCD driver via the SPI interface.
Of course, for each character, you will invert its byte (D0 to D7), split it in 2 bytes of 4 bits significants data bits and zeroes the others bits, then sending the 3 bytes (header, LCDlo and LCDhi) on the SPI.

It works fine... and leave you enough time, within the 100 us sampling period, for sending on the SPI 2 bytes for TLV 5614 DAC refresh and for performing a V/f motor control... DSPs run incredibly fast :-)