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I'm wondering if I've blown my lcd by accident. It's supposed to be a 20 * 4 rows lcd however only row 2 and row 4 seem to light up. Should they not all light up

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  • \$\begingroup\$ By 'light up', do you mean you see black squares? Your LCD probably has 2 controllers, as unixbigot said. And you might have it upside down :-) \$\endgroup\$ – Vincent Van Den Berghe Mar 25 '11 at 9:02
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Some four-row LCDs are actually two controllers with separate enable inputs.

Try writing to all the locations in the data RAM, the memory-address to character-location in these LCDs is not always what you think it is. For example I have a weird 16x1 display that is actually laid out as two disjoint 8-column memory ranges.

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Check your programming and connections. I doubt that you could damage module in such way that only two rows which aren't close together remain functioning.

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  • \$\begingroup\$ but the weird thing is it does it without the avr as well. \$\endgroup\$ – Ageis Mar 24 '11 at 23:26
  • \$\begingroup\$ @Ageis Maybe it is not initialized? They often are half-lit when not initialized. I don't know about 4 rows, but I have had 1 (half of the line lit up) and 2 (other line lit up) line displays. \$\endgroup\$ – varesa Jun 9 '12 at 23:10

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