Newhaven Products > OLEDs

B/W cursor problem on NHD-0420CW-AB3


I'm running this display using 100KHz I2C at 5V (Iv'e also tried 3.5V) and am not observing any data corruption problems.  But I am having trouble with the operation of the B/W bit in the Extended Function Set.  If I write data on the display, then position the cursor over an existing character, then turn on the cursor (Display on with C set), the character is underlined as expected.  If I now issue an Extended Function Set with the B/W bit set, I expect to see the character image pixels inverted (on <-> off).  In fact, what I see is the cursor line vanish and the character stays the same.  If I issue another Display on with C and B set, the entire block alternates between all on (block) and the original character (cursor line still absent). If I now issue an Extended Function Set command with the B/W bit cleared, I get a display with the character alternating with a full-on block - with the cursor line on steady beneath it.  If I turn off the cursor and the blink, then changeing the B/W bit has no visible effect.  This doesn't seem to agree with the description in the manual.  What's happening?


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