A question for all those who have played with LCD displays

[falingtrea]

Isn't there a "Ready" or "Busy" bit sent by the display that you can read to determine when the display is ready to accept more data? I think it is one of the bits returned when you do a read in instruction mode.

[Navaidstech]

Sorry guys, got sidetracked here....

OK, here is the snippet of the code. This is essentially a display routine, which will fire up everytime one of the SPEEDUNITS varaiables changes. This could be as often as 20 ms.
However, I have also noticed this problem with slower update speeds (ie. 1 second).
I'm driving a 4x20 display using 4 data lines.

DisplayResults:
    lcdout $fe,1,$fe,2                                                 ' Clear Display
    lcdout $fe,$80,#Speedunits[0], " FPS"                   ' Display pulse value
    lcdout $fe,$89,#Speedunits[1], " FPS"                   ' Display pulse value
    lcdout $fe,$C0,#Speedunits[2], " FPS"                   ' Display pulse value
    lcdout $fe,$C9,#Speedunits[3], " FPS"                   ' Display pulse value
    lcdout $fe,$94,"Top Speed ",#PeakSpeed," FPS"
    
return

[mackrackit]

lcdout $fe,$94,"Top Speed ",#PeakSpeed," FPS"

You are using 14 spaces in the above with text, then what ever the VAR is using. Add that to the four blank spaces, $94, you might be running out of spaces?
You might try

lcdout $fe,$90,"Top Speed ",#PeakSpeed," FPS"

[Navaidstech]

lcdout $fe,$94,"Top Speed ",#PeakSpeed," FPS"

You are using 14 spaces in the above with text, then what ever the VAR is using. Add that to the four blank spaces, $94, you might be running out of spaces?
You might try

lcdout $fe,$90,"Top Speed ",#PeakSpeed," FPS"

Actually no... with the address $94, the text starts right at the beginning of the line.

[mackrackit]

Well, I am out of ideas. Do you have a data sheet for the display? Might shed some light.

[Acetronics2]

Sorry guys, got sidetracked here....

OK, here is the snippet of the code. This is essentially a display routine, which will fire up everytime one of the SPEEDUNITS varaiables changes. This could be as often as 20 ms.
However, I have also noticed this problem with slower update speeds (ie. 1 second).
I'm driving a 4x20 display using 4 data lines.

DisplayResults:
    lcdout $fe,1,$fe,2                                                 ' Clear Display
    lcdout $fe,$80,#Speedunits[0], " FPS"                   ' Display pulse value
    lcdout $fe,$89,#Speedunits[1], " FPS"                   ' Display pulse value
    lcdout $fe,$C0,#Speedunits[2], " FPS"                   ' Display pulse value
    lcdout $fe,$C9,#Speedunits[3], " FPS"                   ' Display pulse value
    lcdout $fe,$94,"Top Speed ",#PeakSpeed," FPS"
 
return

Hi, Just try to place your " LCDOUT $FE,1 " command OUTSIDE your loop ... ( really needed once only in a program !!! @ top lines i.e. )

so your sub comes to:

DisplayResults:
 
    lcdout $fe,$80,#Speedunits[0], " FPS"                   ' Display pulse value
    lcdout $fe,$89,#Speedunits[1], " FPS"                   ' Display pulse value
    lcdout $fe,$C0,#Speedunits[2], " FPS"                   ' Display pulse value
    lcdout $fe,$C9,#Speedunits[3], " FPS"                   ' Display pulse value
    lcdout $fe,$94,"Top Speed ",#PeakSpeed," FPS"
 
return

Will handle the 50 Hz refreshment, now ...
and note " Home " command already included in the " lcdout $fe,1 " and " lcdout $fe,$80 " commands ...

Alain

[Navaidstech]

Hi guys... sorry for the delay.
I've done some extensive testing on the LCD displays and Acetronics is right! I'm using a single reset at the top of the program now and clear the screen thereafter.
Works like a charm now, no funny characters and everything falls in place perfectly.
Thanks to all of you guys for your input and Acetronics for nailing it.