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HD44780 with SPI interface, possible?

twistedsymphony

New member
I have a whole bunch of of your HD44780 LCDs, I think they're great, I use them in everthing.

I have a custom rig I want to instal one in that already outputs LCD data to an SPI port (yes I know it's a serial port, and yes I know you sell serial LCDs)

my big question is, is there a cicuit I could build to convert the spi data signal to a workable signal for the HD44780 LCD?

"I've heard that you can use a shift register" is pretty much all I've gotten back from people I ask. if there are any places you can point me or insights you could give asside from , get an SPI LCD that would be great.

Thanks in advance.
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CF Tech

Administrator
The shift register approach is all I can think of right off-hand.

If you use the LCD in 4-bit mode, you could do it with a single shift register. You would have to clock out 8 bits twice to complete one write cycle, and since you would be in 4-bit mode you would have a total of four 8-bit SPI writes to get one byte of data into the display.

You might be able to do something clever with the SS pin and reduce that count.
 

CF Tech

Administrator
You would want to use something like the '595.

Basically the 595 gives you 8 extra output pins. You shift the data in using DS and SH_CP. During this time the outputs do not change.

Then when all 8 bits of data are shifted into place, you raise ST_CP and the output pins change to the new state.

Then you would just do updates that would make the 8 pins of the '595 do the same thing your port would do on a normal processor.
 
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