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MSP430FR6922: using the LCD module (4 mux mode, no charge pump, ext. resistor)

Bart
Expert 6310 points
Part Number: MSP430FR6922

Team,

can you explain what do we need to check (register setting, etc.) to enable LCD module with external resistor voltage divider? Our customer wants to use 4 mux mode without charge pump. As of now, we can't turn the LCD on. Below you can see current settings:

Many thanks for your help.

Kind regards,
Bartosz

  • 0
    TI__Guru 60281 points
    Hello Bartosz,

    I believe the register configuration is correct for this mode of operation.
    Since the customer has selected the ACLK, can they confirm this clock is operating at 32KHz?
    Do you know what resistor values they are using for their ladder and what voltage source?
  • 0 in reply to Dennis Lehman
    TI__Expert 6310 points
    Hi Dennis,

    thank you. Additional feedback below:

    Resistors values are 1,5MOhm.
    If LCD is used without external resistors, the display shows characters nicely and purely.
    If LCD is used with external resistors , display shows characters too, but some wrong segments of display are visible (segments which actually shouldn't be seen), some segments of the display that should be shown are only shown partially. It is not a problem of supply voltage, different supply voltages have been tried and the problem persists.

    Kind regards,
    Bartosz
  • 0 in reply to Bart
    TI__Guru 60281 points

    Ok, this sounds like it may be a mis-match between the value of resistors or drive frequency when using external resistors for that specific LCD display.

    You can find more information in application note SLAA654A.

    In addition, this application note SLAA272A will be helpful as it goes into detail about calculating correct resistor values for a given display.

    Let me know if that doesn't solve the issue.

  • 0 in reply to Dennis Lehman
    TI__Guru 60281 points
    Hello Bartosz,

    I'm going to close this thread since it has been a few days since your last response and I'm assuming you have resolved your issue.
    If this is not the case and you need additional help, you can re-open this same thread.

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