VFD Display Brightness & Lcdout

[retepsnikrep]

I have an 44780 compatible display but the brightness control is a little strange.

It requires the RS line to be 1 when sending the brightness commands and LCDOUT seems to always be 0 sending data.

Any thoughts on this.

Can i just set the defined port to 1 before using the lcdout command or will it set it to 0?

Thoughts..

http://www.tme.eu/gr/Document/2b823325898458c8cef30d1c98b906c6/CU20045-UW5J.pdf

[Art]

Lcdout will set RS high to send data and low to send an instruction.
You didn't show the code you tried.
I'd try first simply sending the command as data,
or send it yourself. Just present what the LCD wants to see
In every pin while the Enable pin is high,
then send the Enable pin low.

[towlerg]

You realy can't mess with RS, it is Instruction/Data register select (0=Instruction 1=Data). From the datasheet -
8297

[Art]

Of course you can. You can mess with any of the signal pins as much as you like.
It's only on the falling edge of the Enable pin that the state of all other pins are latched to the LCD.
Hence you can connect multiple LCD modules to all the same pins, but they each need their own Enable pin.

What I think will happen if you set your own state for RS and then send a command with LCDOUT,
is PBP will change straight back to what it wants.

[tumbleweed]

I don't think you have to mess with RS. Looking at the datasheet for the VFD it says this:


One byte data (RS=1) which follows the "Function Set Command" is considered as brightness data.
When a command (RS=0) is written after the "Function Set Command", the brightness control
function is not initiated. Screen brightness is as follows.

So it sounds like the brightness byte goes out as normal data would... you just have to send it right after a Function Set Command byte.
Try something like this:
LCDOUT $FE, $20, $03 'FS=4-bit mode and 25% brightness