LCD locate x, y not working?

[MBB]

I'm using version 98.01 with an 18F452 and #define LCD_IO 2 which uses a 74LS174 shift register and the circuit shown at this link:
http://gcbasic.sourceforge.net/library/DIAGRAMS/2-Wire%20LCD/2-wire%20LCD%2074LS174%20(LCD_IO%202_74xx174%20-%20pre%20Aug2015).JPG

When I write:
locate 0, 0 or locate 1, 0 it prints at the correct location.

When I write :
locate 2, 0 or locate 3, 0 it incorrectly prints at location 2, 4 or 3, 4, respectively.

I'm using 16x 4 displays. One uses the HD44780 chip and the others uses a chip with a paper label over it with UC-16401 on it. I pealed the label off but still couldn't read the number.

I tried this with an 18F4550 but got the same results.

When I used an old 20x4 LCD it worked correctly with both PICs.

Any ideas?

[Anobium]

Slow down the transmission.

Specfic LCD may need slower communications.

#DEFINE LCD_SPEED  SLOW

[MBB]

I tried #DEFINE LCD_SPEED SLOW but it didn't help.

Any other ideas?

[Anobium]

Ummm. Let me check the issue with you.

So, same source code? Same version of Great Cow BASIC. Correct? but, this specific device does not work as expected.

[MBB]

Yes, all the same. This LCD does not work as expected.

[Anobium]

Tried hitting it?

On a more serious note.... Try increasing the delays. This does sound like a timing issue on a specifically slow LCD. These are the parameters I can see. Try settle these to very high value.. maybe 255 then if this fixes the issue bring them down.

Set these in the user program.

#define LCD_Write_Delay 2 us  ' now change all delays
#define slow_us 80

[MBB]

I tried the above suggestion and got the same results. I tried different delay times up to 255 but got the same results.

I also tried in #define LCD_IO 8 mode but still the same results.

[MBB]

In the lcd.h include file is the following SUB:

        Sub LOCATE (In LCDLine, In LCDColumn)
                  Set LCD_RS Off
                  If LCDLine > 1 Then
                            LCDLine = LCDLine - 2
                            LCDColumn = LCDColumn + 20
                  End If

                  LCDWriteByte(0x80 or 0x40 * LCDLine + LCDColumn)
                  wait 5 10us 'test
        End Sub

In the line that reads : LCDColumn = LCDColumn + 20 If I change the "20" to "16"
LCDColumn = LCDColumn + 16

It now works correctly. Is this because I'm using 16x4 display? If so is there some code I can add to my program to over ride the "20"?

[Anobium]

You are correct!

Try the attached.

Add the following to your program.

#define lcd_width 16

[MBB]

Thanks! It works now.

[Anobium]

I will document   and promote to release.

[Anobium]

All sorted.

https://github.com/Anobium/Great-Cow-BASIC-Help/blob/master/source/lcd_width.adoc