C12864WC vs C12864LZ - Driving differences?

bugfixin

• November 18, 2018 03:07

Hi, I have a couple of PCBs I've made with extremely similar circuitry, the only difference is in the pinout / connector for the display, a 30 pin flat flex for C12864WC (NHD-C12864WC-FSW-FBW-3V3-M) and a 28 pin 0.05" header for C12864LZ (NHD-C12864LZ-FSW-FBW-3V3-ND).

Both are using a 4x booster circuit with 1uF ceramic caps, resulting in approximately 12.8V on the vout terminal, with the same capacitance on v0-v4, driven via "4-wire" SPI with the same software using the same configuration values.

The C12864WC has MUCH lower contrast, to the point that it's almost invisible, while the C12864LZ works perfectly. The datasheets do not mention any real differences in software settings (at least not that I've seen), is there a significantly different value (electronic volume, etc?) i should be setting for one vs the other?

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  Alee_S

  • November 19, 2018 15:40

  Hello there!
  
  Please note that contrast voltages for both displays differ, as C12864WC calls for around 10.3 V, while C12864LZ calls for 8.5 V. This may be why you are seeing one display work perfectly, while the other is barely visible. This information is available under the electrical characteristics table on their respective datasheets.
  
  Like you mentioned, I would try to change the electronic volume for the C12864WC display, and see if that makes any difference in its appearance. For command (18), try manipulating the 2nd byte hex value (Electronic Volume Register Set) while staying within its parameters (0x00 – 0x3F), and hopefully that should do the trick!

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