NT7538H C Driver

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Hi there,

I have a sample of the AQM1264C-NLW-BBW-F 128x64 DOTS LCM and I would like to test it. Does anybody have any C code driver?

The specific module use the NT7538H ic.

Thank you.

Michael.

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The datasheet of the driver is here:
http://www.trulydisplays.com/monochrome/specs/Novatek%20NT7538%20Spec.pdf

It should be enough to develop a driver. I developed code for the ST7565V that looks remarkably similar.

If you need to be able to display text at any position, now that's a bit more tricky to do; but that should be quite independent of what driver IC is used.

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Thanks for the datasheet.

I have a simple question? At page 61 of 68 (of the datasheet you sent me) I see that there is a diagram of the connections for SPI Interface between an MCU and the specific ic.

In my LCD datasheet there is the diagram I attach. I really can't understand if I could comunicat with the specific LCM (display) via SPI interface. I ask this because some signals are not supported on the 26 contacts FFC (ex. CS2).

Can anybody help?

Thank you.

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Michael.

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Yes, parallel interface only. The P/S signal that selects between parallel and serial mode is not brought out.

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jayjay,

Thank you.

Would you be able to help me on one more thing?

My design has 2 different power supplies 4.2V and 3V.

- 4.2V/500mA (Buck DC/DC) supply is used for the LCD Backlight which is 4.2V/70mA (max)
- 3V/50mA (LDO) supply is used for the AVR and LCD digital signals needs.

Looking at page 25 of 68 of NT7538 datasheet ("-When not using internal LCD power supply circuits"), the schematic shows that an external power supply can be used without the need of any connection of the CAP, VR and Vo pins. The problem (for me) is that I can't understand if V0, V1, V2, V3, V4 may be connected at the same voltage (4.2V), because it is not clear at the specific schematic. Althought at page 7 of 68 it says that
V0 >= V1 >= V2 >= V3 >= V4 >= VSS2 and at page 46 of 68 it says that V0 (Voltage Regulator Operating Voltage) can be 4 to 14.2V.

So my question is: Could I connect the 4.2V (DCDC, ripple ~ 1%) output to V0, V1, V2, V3, V4 without any connection at pins VOUT, VR, CAP3+, CAP2+, CAP2-, CAP1+, CAP1- ?

Thank you.

I am also wondering if any circuitry of these pins is enclosed in the LCD module. The datasheet does not tell me anything.

Michael.

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No, you cannot connect 4.2V to V1..V4. Each V pin is a tap from a voltage divider that creates the different voltages needed to drive the LCD panel properly. Usually a cap to ground is connected to each of these pins for decoupling purposes.

CAPx+/- pins are the pins for the caps for the voltage step up circuit of the LCD driver chip. It works in the same as the MAX232 for example, but there are a few possible combinations in the number of caps and how they are connected. It depends on the requirements of the actual LCD panel whether voltage doubling, tripling etc is required.

I don't know how much voltage the LCD panel requires, but a Displaytech 32128A is roughly a similar device, and it needs 3 caps, one between CAP1+/-, one between CAP2 +/- and one between VOUT/CAP3- and VDD.

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The display's current consumption at 3Vdc is 1.5 to 2.0mA (max).

Would you be able to tell me your opinion on the display connection (in the .pdf I attach)? It is based on NT7538 datasheet page 59 of 68. The capacitor's values follow the same datasheet suggestions (page 25 of 68 ).

Thank you.

Attachment(s): 

Michael.

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I think you're limited to 3x step-up because the CAP4 pin is not brought out, so wire them up according to page 21, figure 7.

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This must be because the specific LCM datasheet says that
Recommended LC Driving Voltage :
-20ºC 8.6 8.8 9.0 (V)
25ºC 8.1 8.3 8.5 (V)
70ºC 7.6 7.8 8.0 (V)

You are right. 3x Step Up means VOUT = 3 X VDD2 = 9V.

Ultra thanks for your help.

In case you don't have it, once I will finish with the driver I am going to send you the .c and .h file.

Cheers.

Michael.

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I have already successfully interfaced to a Displaytech 32128A which is fairly similar.

Most of the driver code is in the text painting function that can write at any vertical position, not just multiples of 8 pixels. This usually requires a parallel connection to the controller, because most of them do not support read back of the frame buffer with a serial connection.