How do you drive a Serial LCD?

[Mike, K8LH]

Hi Dwight,

I attached the schematic below but I'm afraid the interface in its present form is not very PBP friendly. It was the only way I knew of at the time to control six (6) pins on an LCD with only five (5) PIC output pins. That means you have to drive the display by sending two serial bytes for each LCD byte, each serial byte containing four data bits and an RS bit.

The new design that I'm working should be done soon. It uses full eight bit bytes and recognizes the $FE character (for toggling an RS flag).

Regards...

[Heckler]

Thanks Mike,

That was quite innovative of you to use the incomming data to both talk to the PIC and control the RS line of the LCD!!

nice work.

So is your new design going to use a differend PIC with more I/O pins??

Dwight

[Mike, K8LH]

So is your new design going to use a differend PIC with more I/O pins?

I'm upgrading the interface that uses the 8 pin PIC and actually studying another two slightly more advanced designs.

If you're interested, I've attached the source (assembler) for the 12F635 backpack as well as the source (also assembler) for the 16F1823 on that prototype board. This is the old software and, as I mentioned, probably not very useful for PBP users who are used to having all those wonderful LCD output formatting capabilities.

Happy Holidays! Mike

[Mike, K8LH]

Hi Dwight (and gang),

If you're interested... I just finished testing the upgrade to the 8-pin PIC serial LCD interface and it works great. The mod involved adding an RC integrator/filter (10K + 330pF) between the GP0/D4 pin and the LCD RS pin. Now I can drive all six LCD control pins directly from the little 8-pin PIC which means I can collect serial data, analyze it, and write data to the LCD display any way I want. In short, you should be able to feed the serial interface using the DEBUG, SEROUT2 or HSEROUT commands with all of the same formatting parameters you're using now with the LCDOUT command. I'm pretty geeked (yes, I'm a nerd - LOL).

If anyone is interested, I'll start a new thread in the 'schematic' sub-forum after characterizing and testing the firmware. The only real advantages I can think of for this interface is its size (very small footprint on a project board when using the 2x5 header for a MikroE LCD Adapter board) and its ability to drive four lines of a switch matrix (one additional pin on the host can read four switches, an encoder, etc.).

Cheers, Happy Holidays, Mike

[Mike, K8LH]

Drawing of the updated backpack hardware...

[BobK]

Hi Mike,

Mind if I ask what program you are using to illustrate your drawings?

Thanks,

BobK

[Mike, K8LH]

Greetings BobK.

The drawings were made using the drawing tools in Excel...

The paper silkscreen on the Radio Shack prototyping board was a printout of the silkscreen layer from DipTrace. The paper silkscreen is laminated with plastic tape and glued onto the board.

Cheerful regards, Mike