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Hi all.. Im quite new to 8051. Im doing a project that requires me to display value of a peak voltage on a LCD.
Anyway, Im stuck in testing the LCD. I have connected the LCD(Powertip PC 0802-A), otherwise known as 214-3288, to my 8051 development kit. The kit that im using is C8051F206-TB. I connected databus 0-7 to port 3 and RS to P2.4, R/W to P2.5, and EN to P2.6
I also have gone online to source for programs to display "Hello World" on the LCD. I have found a few in C or asm, but i have learnt the basic of assembly language, so i don't really understand C language.
Below is a program i found in 8052.com
$include (c8051f200.inc) CSEG AT 0000H LJMP MAIN CSEG AT 0100H MAIN:LCALL CONFIG LCALL INIT_LCD LCALL CLEAR_LCD LCALL HELLO CONFIG:MOV PRT0MX, #000H ; PRT0MX: Initial Reset Value MOV PRT1MX, #000H ; PRT1MX: Initial Reset Value MOV PRT2MX, #000H ; PRT2MX: Initial Reset Value MOV P2MODE, #0FFH ; Input Configuration for P2 MOV PRT3CF, #0FFH ; Output configuration for P3 INIT_LCD: CLR P2.4 MOV P3,#38H SETB P2.6 CLR P2.6 LCALL WAIT_LCD CLR P2.4 MOV P3,#0EH SETB P2.6 CLR P2.6 LCALL WAIT_LCD CLR P2.4 MOV P3,#06H SETB P2.6 CLR P2.6 LCALL WAIT_LCD RET HELLO: LCALL INIT_LCD LCALL CLEAR_LCD MOV A,#48H LCALL WRITE_TEXT MOV A,#45H LCALL WRITE_TEXT MOV A,#4CH LCALL WRITE_TEXT MOV A,#4CH LCALL WRITE_TEXT MOV A,#4FH LCALL WRITE_TEXT CLR P2.4 MOV P3,#0CAH SETB P2.6 CLR P2.6 LCALL WRITE_TEXT MOV A,#57H LCALL WRITE_TEXT MOV A,#4FH LCALL WRITE_TEXT MOV A,#52H LCALL WRITE_TEXT MOV A,#4CH LCALL WRITE_TEXT MOV A,#44H LCALL WRITE_TEXT WAIT_LCD: CLR P2.6 ;Start LCD command CLR P2.4 ;It's a command SETB P2.5 ;It's a read command MOV P3,#0FFH ;Set all pins to FF initially SETB P2.6 ;Clock out command to LCD MOV A,P3 ;Read the return value JB ACC.7,WAIT_LCD CLR P2.6 ;Finish the command CLR P2.5 ;Turn off RW for future commands RET CLEAR_LCD:CLR P2.4 MOV P3,#01H SETB P2.6 CLR P2.6 LCALL WAIT_LCD RET WRITE_TEXT:SETB P2.4 MOV P3,A SETB P2.6 CLR P2.6 LCALL WAIT_LCD RET END
You want a short delay between taking EN high and taking it back low. The longer delays should come after you take EN low. You need to change RS according to whether you are writing instructions or writing display data. In the example code you posted earlier you never take RS high to write display data.
"you never take RS high to write display data."
I did it in the "LCALL WRITE_TEXT"
WRITE_TEXT: SETB RS CLR RW MOV DAT,A SETB EN LCALL DELAY CLR EN
You mean the delay i use between "SETB EN" and "CLR EN" is too long? I have to use another shorter delay? And after "CLR EN" i have to use the longer delay before i can continue with other instruction?
condensing Dan's post
read and follow the timing requirements stated in the datasheet.
Your posts "does this work" "why does this not work" show nothing but the fact that reading a datasheet evidently is below your dignity.
Erik
'You mean the delay i use between "SETB EN" and "CLR EN" is too long? I have to use another shorter delay?'
I'd change the wording to be "unnecessarily long". If I recall correctly, the data sheet does not indicate a maximum EN pulse width, only a minimum.
'And after "CLR EN" i have to use the longer delay before i can continue with other instruction?'
Right.
I see. Thx Guys.
Erik, I have read the datasheet, but i do not really understand it, thats why i post on this forum. I have never program an LCD before. This is my 1st time programming an LCD. I did not know that timing was so important. Now that i know, it will be easier for me to program. Even though theres some things that I'm still not sure, but i'm sure im will be able to figure that out.
I have read the datasheet, but i do not really understand it Then I suggest that instead of posting like you do, you ask specific questions related to what in the datasheet you do not understand. if you do not develop the skill of understanding a datasheet you will be equally lost at your next project.
I did not know that timing was so important can you elaborate on why that is so, that might make some answers more 'digestible' to you.
before asking datasheet related questions, provide a link to the datasheet for your display.
At 1st, i did not know that i need to make sure that my Power reset rise time and the EN timing need to satisfy the datasheet timing. I thought the timing in the datasheet is just there to tell me how long it will take.
I see.. I will take note of that.
Thx.
See it as a two-way contract.
Some parts of the data sheet specifies what you must fulfill. Some parts of the data sheet specifies what the display will do for you. The display will only do its part if you do your part.
Ok.
I followed what Dan said, I can see the cursor appearing at the 1st position of the 2nd line and disappeared, and after a few seconds it appeared on the 6th position. It might be printing the word "WORLD", but i cannot see it. I'm quite sure that that i have satisfy the timing required on the datasheet. Or do i have to make a longer delay at the "Move cursor" instruction?
This is the delay i use for the "move cursor" and after the "CLR EN" instruction, DELAY1 is the delay i used between SETB EN and CLR EN:
DELAY: MOV R1,#06H D1: MOV R2,#0FFH D2: MOV R3,#0FFH D3: DJNZ R3,D3 DJNZ R2,D2 DJNZ R1,D1 RET DELAY1: MOV R1,#01H D1: MOV R2,#0FFH D2: MOV R3,#OFFH D3: DJNZ R3,D3 DJNZ R2,D2 DJNZ R1,D1 RET
"... after a few seconds it appeared on the 6th position. It might be printing the word "WORLD", but i cannot see it."
A few seconds is quite a long time to display 5 characters. Firmware written to satisfy worst case timing for a typical HD44780 controlled display should take under 1ms to display 5 characters. How long do your delays need to be? How long are they actually delaying? Have you measured their durations?
"Or do i have to make a longer delay at the "Move cursor" instruction?"
We normally configure our displays, the display controller automatically increments the DDRAM address when a character is written to DDRAM and there is no need for an explicit "move cursor" instruction.
The "Move Cursor" instruction is to move the cursor to the 2nd line.
25Mhz processor and the "DELAY" i'm using, should give me about 37us delay. From the datasheet, most instructions took 40us(max) to execute.
I have tried values for R1 ranging from "#01H" to "#0FH". It still have the same problem. "Hello" on the 1st line and nothing on the 2nd. I wonder whether is it my power supply to the LCD is not enough.
Ok. I have tried inputting a 5V supply directly from a DC volatge supply but in vain.
I have tried printing "WORLD" on the 1st line, but it also cannot print. Does it have something to do with my connection with the C8051 development kit?