1
\$\begingroup\$

I am trying to get an LMB204BDC LCD screen working with a PIC16F877a and the Flex 4x20 Driver (I'm programming in CCS BTW), however for some reason the text is not displayed. Before, I mistaked the datasheet for saying to attack a 5k ohm resistor from the contrast pin to +5v, so I did that and later realized it said from the contrast pin to v0, I connected a 3k ohm resistor and the first and third lines only have faint boxes, might I have damaged the display?

Thanks in advance.

\$\endgroup\$
  • 1
    \$\begingroup\$ 1) Your contrast is still not right. Use a trimpot instead of a fixed resistor. That way you can just turn it to dial in the correct contrast. 2) Solid blocks are normal if the LCD is not initialized properly, IIRC. \$\endgroup\$ – dext0rb Jun 7 '12 at 21:47
1
\$\begingroup\$

With the info provided an exact answer can't be given, but:

As mentioned by dextorb, The black boxes are normal for a non-initialised display, and his advice to use a 5k pot instead so you can trim the contrast is good (advised in the LMB204BDC datasheet too)

Damage - I think your display is very likely to be okay if you had a 5k resistor between +5V and V0.
Of course make sure you (double) check all connections (voltages, datalines signals, etc) carefully.

If all looks okay, but only black boxes are seen, I think the most likely thing is the display is just not initialised properly. Checking the datasheet it uses a ST7066U controller. Read through the ST7066U datasheet and make sure you are following the initialisation procedure (examples start on p.23) correctly. If using some library check what controllers it works with, and/or look at the initialisation function to compare with datasheet advice.

Sometimes these controllers can be pretty sensitive to timings, so make sure you follow the instructions as closely as possible (e.g. where it says things like "wait > 50us", "wait > 1ms", etc)

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.