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MSPFG437 and Softbaugh SBLCDA4 LCD display

Yousef Debs
Prodigy 80 points
Other Parts Discussed in Thread: MSP430FG437

Hello,

I'm trying to interface the Softbaugh SBLCDA4 with the MSP430FG437 that we're debugging with the USBFET430UIF tool. Looking at the schematic provided in SLAA458, we have the S0-S21 pins connected appropriately and COM0-COM4 connected. We have a resistor ladder of 680k resistors connected to R33, R23, R13, and a 1k resistor connected to R03 which is then grounded.


It doesn't appear to be powering on whatsoever. There are zero lit segments or flickering.Within the SLAA458 document, it reads:

"The voltages required for the LCD signals are supplied externally to pins R33, R23, R13, and R03. Using an equally weighted resistor divider ladder between these pins establishes the analog voltages."

On the schematic there is no indication of any external power to these ports. I attached an image of the resistor ladder from the schematic below.

This is the function in the code that appears to power the LCD:

void set_LCD(void)
{
    volatile unsigned int i;
    for(i=0;i<11;i++)                         // Clear LCD memory
    {
      LCDMEM[i] = 0x00;
    }   

    /* Turn on the COM0-COM3 and R03-R33 pins */
    P5SEL |= (BIT7 | BIT6 | BIT5 | BIT4 | BIT3 | BIT2);

    LCDCTL = 0x7F;                          // Selected function: Analog generator on
                                            // Low impedance of AG
                                            // 4Mux active
                                            // all outputs are Seg
                                            // S0-S23 are LCD segment lines
    BTCTL = BTFRFQ0;                        // Start Basic Timer 1s + LCD 64Hz
}

  • 0
    Prodigy 80 points

    Just to clarify:

     

    I have J6 on the fet debugger board open as instructed.

    I ran sample code to make the LCD work from the TI website and it still does not power the LCD. Any chance I'm missing something silly?

  • 0 in reply to Yousef Debs
    Prodigy 80 points

    I thought this was a relatively simply question.

    I read the MSP430 user guide and it indicates that the R33-R03 pins generate an analog square-like signal when turned on which is done through this line:

    P5SEL |= (BIT7 | BIT6 | BIT5 | BIT4 | BIT3 | BIT2);

    Why would the guide then say:

    "The voltages required for the LCD signals are supplied externally to pins R33, R23, R13, and R03. Using an equally weighted resistor divider ladder between these pins establishes the analog voltages as shown in Table 25−1"

    And

    "R33 is a switched-VCC output."

    How is it switched on/off? I'm assuming by code, but when i skip to the lcd function in the code I never measure any voltage out of pin 51 (R33). Is this statement implying that we must supply an external voltage to the resistor ladder to generate the analog signal from them? That seems to make no sense and also does not correlate to what is shown in the schematic. Perhaps it is worded awkwardly or I'm simply misunderstanding it.

    Please, any help would be greatly appreciated. This is my first time using an external LCD with an MSP430 chip and so far it seems to have me stumped.

    Rgds,

    Yousef.

  • 0 in reply to Yousef Debs
    Guru 227245 points

    I haveN't worked with the LCD, so I cannot answer your questions, but sinde nobody else answered so far, here a hint:

    Check the circuitry of the available experimenter boards. Schematics are available (see the product pages). You can get a hint for the hardware setup here.
    And in the demo software is a starting point for the usage.

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