Interfacing a 16x2 LCD with SPI, Getting Characters into the Second Row

Question

I'm using an MSP430 MCU to read analog signals and display the results on an LCD with a SPI connection. The LCD is a 16x2 that is connected according to the SPI connection details on the Datasheet and uses a Hitachi HD44780 driver. I can fill up the 16 characters of the first row no problem. When I go over 16, the last character does not display(as expected) even if I extend the char array that holds the string that I want to print. The problem is that the second row never displays anything. When there are no characters in a position in the first row, there is still a faint background in all positions, but the second row is always continuously blank. Below are the functions that are used in printing. What am I doing wrong?

I know the wiring is correct and the LCD is functional. To test these, I wired the display to an arduino to test, since the code is much easier and I was able to display characters in bow rows. The non-descriptive variables are defined by the MSP430 source files and include registers, buffers, and other controls to put the device in SPI communication mode.

void AlignLaserTarget()
{

    int i,k, j;
    struct testResults *ptestResults;
    char mess1[17]; //changed from 8 to hold 16 characters

    ptestResults=getTestResults();

    // reset global vars
    timeI1=0;
    timeA=0;
    i=starResults.ch1Amplitude; //analog integer value to be printed on LCD
    j=starResults.ch2Amplitude; //same
    k=starResults.ch3Amplitude; //same, but should go in second row
    sprintf(mess1,"1:%i 2:%i", i, j);
    stringTo_lcd8( mess1);
}

void stringTo_lcd8( char* lcdString )
{
    int i;

        LCD_COMMAND_MODE;       // display code
        timer_us(20);
        write_lcd8( 0x01); // clear display
        timer_ms(2);
        LCD_DATA_MODE; //enable data sending pin

        for ( i=0; *lcdString !=0 ; ++i)
        {
            write_lcd8( *lcdString);
            ++lcdString;
        }                       // end of display code

        timer_us(10000);    // 10ms delay . should not be needed as normal interval between counts is at least 75 ms or 12 in. at 800ft/min rate
}
//*******************************************************

void write_lcd8( unsigned char lcdbyte)
{
      UCA0IFG &= ~UCTXIFG;  // CLEAR FLAG
      UCA0CTL1 |= UCSWRST;                      // **Put state machine in reset**
      UCA0CTL0 = UCMST+UCSYNC+ UCMSB+ UCCKPH;
      UCA0BR0 = 0x80;                           // /hex80
      UCA0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**
      timer_us(100);
        LCD_CHIP_ENABLE;            // LCD enable pin output
        timer_us(20); // added trp
        UCA0TXBUF =lcdbyte;
        timer_us(150);
        while (!(UCA0IFG&UCTXIFG));
        UCA0IFG &= ~UCTXIFG;  // CLEAR FLAG
        LCD_CHIP_DISABLE;
        timer_us(30);
          UCA0CTL1 |= UCSWRST;                      // **Put state machine in reset**
          UCA0CTL0 |= UCMST+UCSYNC+ UCMSB+ UCCKPH;
          UCA0BR0 = 0x02;                           // /2
          UCA0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**

}

Answer 1

I think you have to design some more driver function before using for application logic. I have taken sample code to set cursor position

void Lcd8_Set_Cursor(char line, char col)
{
    if(line == 1)
      Lcd8_Cmd(0x80 + col);
    else if(line == 2)
        Lcd8_Cmd(0xC0 + col);
}

Then use same in your printing logic. When ever length exceeding 16 you can switch line and start writing.

Answer 2

The HD44780 is expecting 40 characters per row, so I just added spaces to fill up the first row and then wrote the characters for the next row. I'm sure there is a better solution but this was fast and it worked. I also had to change the initialization specifications for a two row configuration.