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MSP430F6736A: Highlighting inactive segments

Part Number: MSP430F6736A

Connected segment LCD display, and found the backlight of inactive segments, what could be the problem?

LCD_C_off(LCD_C_BASE);   //Initialize LCD
LCD_C_initParam initParams = {0};
initParams.clockSource = LCD_C_CLOCKSOURCE_ACLK; // часовое тактирование
initParams.clockDivider = LCD_C_CLOCKDIVIDER_10;//fps_value[settings.fps%32];//4;//1
initParams.clockPrescalar = LCD_C_CLOCKPRESCALAR_4;//8
initParams.muxRate = LCD_C_8_MUX;//LCD_C_4_MUX; // 8 фаз
initParams.segments = LCD_C_SEGMENTS_ENABLED;
LCD_C_init(LCD_C_BASE, &initParams);

LCD_C_setPinAsLCDFunctionEx(LCD_C_BASE, LCD_C_SEGMENT_LINE_0,
LCD_C_SEGMENT_LINE_27); // 0..27
LCD_C_setVLCDSource(LCD_C_BASE, LCD_C_VLCD_GENERATED_INTERNALLY,
LCD_C_V2V3V4_GENERATED_INTERNALLY_NOT_SWITCHED_TO_PINS, 
LCD_C_V5_VSS); 

LCD_C_setVLCDVoltage(LCD_C_BASE,contrasrt_value[settings.contrast]); 

LCD_C_selectChargePumpReference(LCD_C_BASE, LCD_C_INTERNAL_REFERENCE_VOLTAGE);
LCD_C_enableChargePump(LCD_C_BASE);

LCD_C_configChargePump(LCD_C_BASE, LCD_C_SYNCHRONIZATION_ENABLED, 0);

LCD_C_clearMemory(LCD_C_BASE);
LCD_C_on(LCD_C_BASE);

  • Hello Andrey,

    Sorry for the delay due to the holidays, were you able to improve your LCD performance?  It looks like possibly your contrast is to low, how are you controlling it?

    The actual LCD signal looks okay at first glance, it's 1/3 biasing.  Is your LCD a 1/3 bias LCD?   

    Thanks,

    JD

  • Hello JD

    we adjust the contrast by changing the output signal voltage, here is a line of contrast adjustment code: lcd_c_setvlcdvoltage(LCD_C_BASE,contrasrt_value[settings.contrast]);.

    Does the msp430f6736a still have the ability to change the output signal to adjust the contrast? Yes, perhaps the LCD display itself is of poor quality. we connected this display to the STM32L496 it has a 1/4 bias but it didn't get any better. But stm32l496 has more tools to change the output signal.

    Thanks for your reply.

  • Hey Andrey,

    Were you able to make any improvements on the display?  

    My understanding is the contrast is effected by the bias of the LCD signals, as well as voltage of the signal being applied to the LCD.   Both of these effect the voltage being applied to 'off' segments.  As you pointed out, the MSP430 has some abilities to try and adjust the contrast by adjusting the reference voltage for the LCD signals.  

    If you have the specification for the LCD screen, I would look for it's expected bias level and just match it.  If still having contrast issues, look at adjusting the voltage in software, or try adjusting the external VCC even.  

    Let me know how it's going.

    Thanks,

    JD