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LCD JHD204A FPGA interface

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a.singh123

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I am trying to interface JHD204A LCD display with my FPGA board. The problem is that LCD works with only 5V power supply, and my FPGA supplies 3.3V only. I supplied power from another source of 5V, and connected the grounds of both togeteher. LCD display is showing bright light, but no data is shown which I sent from FPGA controller.
In the FSM, I have sent the initialization commands followed by my data, but no change. I doubt the signal voltage levels from FPGA are not sufficent to drive LCD, since it is only 3.3V signal. Please can anyone help me.

Regards,
Abhishek
 

Hi,

Signal levels:
There are datasheets for such informations.
Read both devices datasheets regarding their I/O levels.
Vih, Vil, Voh, Vol.

Then you know for sure if they fit or not.

If they don't fit, then you need level translators.


***
We can't verify your system, because we don't know FPGA type, FPGA I/O setup and so on...


Klaus
 

The datasheet of the LCD seems to indicate a the VIH is 2.2V so the FPGA outputs should work fine with the LCD. I'm assuming there are no outputs from the LCD and if there are you didn't connect them to the FPGA (that would damage the FPGA I/O).
 

ads-ee said:
The datasheet of the LCD seems to indicate a the VIH is 2.2V so the FPGA outputs should work fine with the LCD. I'm assuming there are no outputs from the LCD and if there are you didn't connect them to the FPGA (that would damage the FPGA I/O).
Click to expand...

Hello, i dont have any signals frm LCD entering to fpga (input to fpga). There are 4 signals only frm fpga to LCD. They are R/S, EN, W/R and the 8 bit data signals. These 4 signals are 3.3V i/o levels. I gave 5V power frm another source, not frm fpga and connected all the gnds together. The data sent frm fpga is displayed but it gets displayed when i disconnect fpga power. I dont undrstand whats the issue.
Also data gets displayed once abd then it gets deleted.
 

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