4mux LCD with MSP430FE432A

Purushottam Kamat

Other Parts Discussed in Thread: MSP430FE423A

I am using a 4-mux LCD display with MSP430FE423A. I am trying to have, 1 seg darkened and other 3 white(transperant), of the 4 muxed segs, . But, the 3 segs that supposed to be white also became faintly grey. That is the seg to be dark is very black. But seg to be white is grey. Where could be reason for this? Another observation is that the R33 voltage is 1.35V. Is that OK? or the IC / resister ladder is damaged or something? (R03 is grounded) What should I do? Change fLCD? or change R-R ladder values? Anything else I should check?

over 11 years ago

0 Jens-Michael Gross over 11 years ago

Guru 227245 points

Purushottam Kamat said:
But, the 3 segs that supposed to be white also became faintly grey

Other than LED muxing, LCD segments require an AC voltage to go active. SO the segment signals and the COM lines dance a jitterbug to provide a strong AC signal for the active segments while keeping the signal as much DC as possible for the inactive ones. However, real DC for inactive segments is impossible. See the users guide chapter about the LCD controller. It shows the generated signal forms for segments and COM lines for different mixing levels.

0 Purushottam Kamat over 11 years ago in reply to Jens-Michael Gross

Prodigy 180 points

what is the expected voltage on R33? (if measured as open)

0 Jens-Michael Gross over 11 years ago in reply to Purushottam Kamat

Guru 227245 points

Purushottam Kamat said:
what is the expected voltage on R33? (if measured as open)

Depends on configuration. I have no idea. Doesn't the datasheet tell?

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4mux LCD with MSP430FE432A