HD44780 based LCD display shows half-black, half-blank

I have been trying to get a HD44780 LCD display to work for multiple times. The first time was by parallel port from a computer, then multiple times using different PIC uCs. I am only able to get the display to show half of the dots (the right side of the screen) as black, and the left side as blank/white. I read from the internet that it means the display is not initializing properly.

The display is Tianma TM161A/B

    setData(0b00110000); // INIT     strobeE();      DelayMs(5);      setData(0b00110000); // INIT     strobeE();      DelayMs(5);      setData(0b00001111); // ON/OFF     strobeE();      DelayMs(5);      setData(0b00000001); // CLEAR     strobeE();      DelayMs(5);      setData(0b00000110); // ENTRY MODE     strobeE();  void strobeE() {     mPORTDSetBits(E);     DelayMs(1);     mPORTDClearBits(E); } 

I have used a logic analyzer, a logic probe and a multimeter to check if the connections between the PIC and the LCD are correct. I think they are.

A ( bad ) picture of my timings on a logic analyzer; HD44780 based LCD display shows half-black, half-blank

Link to the datasheet

What am I doing wrong?

Replay

The problem with the display not initializing was because of a loose wire. It was either RS or RW, that was left floating.

My logic analyzer showed it being in the low state, but seems the LCD's controller thought otherwise. (Different kind of input)

A tip:
Check your wirings: not connected != input driven low

A logic probe, which emits a high, or low pitch sound depending on the signal, helped me find the problem. It did not give any kind of sound at all on that pin.

Check your "function set" word (0b00110000). bits 2 and 3 (N and F in datasheet) set display shape. If they are set incorrectly, part of display will not function -- try all 4 combinations.

Category: pic Time: 2012-06-09 Views: 5

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