LCD control lines in Version 2 development board.

[KeithSloan]

I am trying to convert a program that uses

;* 1 A2 - LCD Register Select *
;* 2 A3 - Vcc for LCD *

;* 10 B4 - LCD Data 4 *
;* 11 B5 - LCD Data 5 *
;* 12 B6 - LCD Data 6 *
;* 13 B7 - LCD Data 7 *

;* 17 A0 - LCD Enable *
;* 18 A1 - LCD Read/Write *

What are the equivalent on the Version 2 development Board and I guess the LCD E-Block.

Thanks

[Benj]

Hello

The equivalent for the Dev boards and E-Blocks are as follows.

LCD Data 4 - B0
LCD Data 5 - B1
LCD Data 6 - B2
LCD Data 7 - B3
LCD RS - B4
LCD E - B5

LCD VCC - 5V
LCD R/W - GND

Note that the E-Block does not have to be connected to port B.

[KeithSloan]

LCD R/W - GND

Does this mean I can only write to the LCD NOT read

[Steve]

yes - the dev board (and E-Blocks) LCD is configured to be write-only.

[KeithSloan]

Pity as it would have only taken one more control line and would have allowed scrolling etc.

Looks like I will have to give up porting the program I had in mind as it does read from LCD as well as write.

[Steve]

Left-right and right-left scrolling (and almost any other LCD function) can be achieved without needing to read from the device.

[KeithSloan]

Steve

Yes I was aware that scrolling was possible by sending commands, but that's not the way the original program was written. Obviously more work to convert. I will have a word with the original Author.

Keith

[Steve]

Scrolling text that is already written onto the LCD display is very easy to achieve. The command "0x07" sets the display up to allow scrolling and the commands "0x18" and "0x1C" shift the display in either direction.

I hope this helps.

[KeithSloan]

What happens to the second line when you scroll left/right? Does it wrap?
I think the application needs to insert text in the top left and characters would fall off the bottom right.

[Benj]

Hello Keith

Two line alphanumeric displays all have an 80 character buffer.

On a top line you have locations 0 - 39
On the bottom line you have locations 40 - 79

When you write to the display you start at location 0 and then each subsequent write will be placed into the next location.

Therefore you can fill up all 80 characters if you like and scroll across the display. You can also jump to points in the memory. eg shift the display right 16 places.

The thing to note is that the memory does not change whilst scrolling. It is simply the display that is displaying a different portion of the memory.

Therefore if you move the cursor to location 0 and send a character you are not shifting the data in the buffer but merely overwriting the data in memory location 0.

If you wanted a rolling buffer then you would have to code this on the pic by using an array. The display (visible portion of memory 0-15 & 40-55 on 2x16 line LCD) would have to be completely rewritten each time from the contents of the array.

I hope this helps.