MSP430FR6047: Some of the LCD segments not working

Hi, Sagar, 

What is the COM, and bias for the LCD? 

If you are using the LCD module internal charge pump to generate the LCD bias voltages, you should connect 4.7uF on the pin LCDCAP./R33.  

If you are using external resistor divider to generate LCD bias voltages, you should connector resistor on pin LCDCAP/R33 pin. 

Please refer to the pin description, the section 5.13.9 and 7.2.2.4 in the MSP430FR6047 datasheet for details. There is also detailed description for operation theory and register configuration in user's guide slau367. 

Thanks, 

Lixin 

Hello Lixin,

I am not sure about the bias voltages. How would I be able to check that. I am using a resistor divider with the schematic and code attached. I had tuned the R19 resistor value to set the contrast I require. I am using the default code inititalization as for EVM430-FR6047. I think the internal charge pump is not used. Do you suggest any changes both from schematics and firmware perspective for a stable result? Or some experimentation required?

void hal_lcd_Init(void)
{
    LCD_C_initParam initParams = {0};
    initParams.clockSource = LCD_C_CLOCKSOURCE_ACLK;
    initParams.clockDivider = LCD_C_CLOCKDIVIDER_1;
    initParams.clockPrescalar = LCD_C_CLOCKPRESCALAR_16;
    initParams.muxRate = LCD_C_4_MUX;
    initParams.waveforms = LCD_C_LOW_POWER_WAVEFORMS;
    initParams.segments = LCD_C_SEGMENTS_ENABLED;

    /*
    * Select Port 6
    * Set Pin [4:7] as LCD COM, [1:3] as R03/R13/R23
    */
#ifdef LCD_USE_RES_LADDER
    GPIO_setAsPeripheralModuleFunctionInputPin(
        GPIO_PORT_P6,
        GPIO_PIN4 | GPIO_PIN5 | GPIO_PIN6 | GPIO_PIN7 | GPIO_PIN1 | GPIO_PIN2 | GPIO_PIN3,
        GPIO_TERNARY_MODULE_FUNCTION
        );
#else
    GPIO_setAsPeripheralModuleFunctionInputPin(
        GPIO_PORT_P6,
        GPIO_PIN4 | GPIO_PIN5 | GPIO_PIN6 | GPIO_PIN7,
        GPIO_TERNARY_MODULE_FUNCTION
        );
#endif
    LCD_C_init(LCD_C_BASE, &initParams);
    // LCD Operation - VLCD generated internally, V2-V4 generated internally, v5 to ground

    LCD_C_setPinAsLCDFunctionEx(LCD_C_BASE, LCD_C_SEGMENT_LINE_0,
                                LCD_C_SEGMENT_LINE_31);

#ifdef LCD_USE_RES_LADDER
    LCD_C_setVLCDSource(LCD_C_BASE,
                        LCD_C_VLCD_GENERATED_INTERNALLY,
                        LCD_C_V2V3V4_GENERATED_INTERNALLY_SWITCHED_TO_PINS,
                        LCD_C_V5_SOURCED_FROM_R03);
#else
    LCD_C_setVLCDSource(LCD_C_BASE,
                        LCD_C_VLCD_GENERATED_INTERNALLY,
                        LCD_C_V2V3V4_GENERATED_INTERNALLY_NOT_SWITCHED_TO_PINS,
                        LCD_C_V5_VSS);
#endif

#ifdef LCD_USE_CHARGEPUMP
    LCD_C_setVLCDVoltage(LCD_C_BASE,
                        LCD_C_CHARGEPUMP_VOLTAGE_3_02V_OR_2_52VREF);
                        //LCD_C_CHARGEPUMP_VOLTAGE_2_60V_OR_2_17VREF);
                        //LCD_C_CHARGEPUMP_VOLTAGE_3_44V_OR_2_87VREF);
    // Enable charge pump and select internal reference for it
    LCD_C_enableChargePump(LCD_C_BASE);
    LCD_C_selectChargePumpReference(LCD_C_BASE,
                                    LCD_C_INTERNAL_REFERENCE_VOLTAGE);
#else
    LCD_C_setVLCDVoltage(LCD_C_BASE,
                        LCD_C_CHARGEPUMP_DISABLED);
    LCD_C_disableChargePump(LCD_C_BASE);

#endif

    LCD_C_configChargePump(LCD_C_BASE, LCD_C_SYNCHRONIZATION_ENABLED, 0);

    // Clear LCD memory
    LCD_C_clearMemory(LCD_C_BASE);

    //Turn LCD on
    LCD_C_on(LCD_C_BASE);
}

Hi, 

Bias voltages are the different voltage levels on the LCD signals. In the LCD chapter of user's guide slau367, you can find the LCD signals as following figure for 4COM LCD. 

You can measure the voltages on the LCD pins or the 4 pins R03/R13/R23/R33 to check if the voltage levels are meeting the LCD specification. 

From the code, you are using the define micro to enable the charge pump or use the resistor divider to generate the bias voltages. You can also try to use both ways to generate the bias voltages to see which is correct.

The EVM hardware files and source code are good example. User's guide slau367 has detailed information about the LCD operation and configuration. Please study the materials to find solution for your issues. 

Thanks, 

Lixin

Hello,

Yes I am trying to understand in a better way. Kindly explain the two statements its unclear to me.

Regards,
Prudhvi Sagar

Hi, 

This is the register LCDREXT description. 

When LCDREXT set to 1, internal charge pump will output voltages on V2 to V4. Section 30.2.5.2 in the user's guide has the detailed description. 

Hello,

I am confused with the statement "switched to external pins".

Regards,

Prudhvi Sagar

There are switches to control the output the V2-V4 to external pins: R13, R23, R33. 

Thanks, 

Lixin 

Hello,

So this is used to utilize the Resistor divider to set the bias voltage? Can the internal charge pump and the resistor divider be activated simultaneously. So can the pin R33 be connected to a resistor and a capacitor simultaneously? 

Regards,

Prudhvi Sagar

Hi, 

There are 2 options for bias generation: 

1. Use internal charge pump, with capactor on R33 pin. 

2. Use external resistor divider. 

These 2 options cannot be enabled at the same time. 

So pin R33 cannot be connected to a resistor and a capacitor simultaneously. But for option 2 (resistor divider), the capacitor on R33 may not hurt the bias performance, which works as a de-coupling cap. Then that is fine to have the capacitor. 

Thanks, 

Lixin 

Hello Lixin,

Thank you for the quick reply. So to summarize the situation, given V5 is fixed to R03 and no external bias is used it leads to 3 sitautions: (?)

1. Using Charge pump + Not using Resistor divider.

2. Not using Charge pump + using Resistor divider.

3. Not using Charge pump + Not using Resistor divider.

Kindly confirm. 

Regards,

Prudhvi Sagar.

Hi, 

I think your understanding is right. 

Options 1 and 2 can work for LCD bias generation. Option 3 cannot generate the bias for LCD so that option 3 means no enabled LCD.  

Thanks, 

Lixin 

Hello Lixin,

I have tried the 3rd option as attached, it still works. My main issue is on prolonged usage, some of the segments die and do not work on a reset as well. It requires a complete re-program for it to work. Is this an issue which you are already aware of? Why does this happen? I am planning to run the devices with the 3 options and then check which one doesnt die.

Regards,

Prudhvi Sagar.