HD44780 with SPI interface, possible?

[twistedsymphony]

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]

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.

 

[twistedsymphony]

cool thanks
do you think something like this would work? http://focus.ti.com/lit/ds/symlink/cd74act164.pdf
or this
http://www.philipslogic.com/products/hc/pdf/74hc_hct595.pdf

I guess I'm still a bit confused as to how the register actually connects to the LCD. Do you know of any good resources with spi to parallel diagrams?

 

[CF Tech]

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.