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Ray B
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Joined: 16/02/2007
Location: Australia
Posts: 219

Posted: 03:15am 03 Jul 2011

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The following articles will explain all about LCD displays
http://www.epemag.wimborne.co.uk/lcd1.pdf
http://www.epemag.wimborne.co.uk/lcd2.pdf

Following is my rewrite of Geoff's LCD code to provide more comments and examples of sending variables in other lines of test to the LCD and also some of my idiotic diagnostic strinds to print on my PC so I can see what the MM is doing when.

Code follows:

10: ' Filename "RayLCD_4.bas"
15: ' this explains a lot of the LCD commands
20: GOSUB 11000 ' Initialise the LCD
'
' LCD is now setup to receive characters and display them
'
25: FOR n = 1 TO 100
30: LCD_line1$ = " Hello World "
35: LCD_line2$ = " Maximite LCD "
40: GOSUB 12000 ' to routine to send text characters to LCD
'
' we have now sent a couple of lines to LCD
' now print out some diagnostic text & sent 2 diff rows of text inc a variable TIME$
'
45: PRINT , "loop number", n , LCD_line1$, LCD_line2$ 'for diagnostic purposes
50: PAUSE 1000 'for diagnostic purposes
55: lCD_line1$ = "time = "+TIME$ ; 'load new string & add TIME$
60: LCD_line2$ = "qwerty " 'just some more text for diagnostic purposes
65: GOSUB 12000 ' to routine to send text characters to LCD
70: PRINT , "loop number", n ,LCD_line1$, LCD_line2$
75: PAUSE 1000
80: NEXT n
85: END
90: '
95: '
10000: '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' ''''
10010: ' LCD driver for standard 16 x 2 LCDs
10020: ' Geoff Graham, March 2011
10030: '
10040: ' For example: futurlec.com LCD16X2
10050: ' altronics.com.au Z7001
10060: ' jaycar.com.au QP5512
10070: '
10080: ' To use:
10090: ' - execute GOSUB 11000 to initialise display
10100: ' - then load the text strings into the
10110: ' variablesLCD_line1$ and LCD_line2$
10120: ' - execute GOSUB 12000 to display the text
10130: '
10140: ' See the file lcd.pdf for the schematic.
10150: ' Maximite pin 11 is LCD line RS (4) which is 'Register Select' a L = means data lines will be COMMANDS & H = means data lines = characters
10155: ' Maximite pin 12 is LCD line EN (6) which is 'Enable' data is transferred to LCD on a H to L transition
10157: ' LCD R/W line is always L to vreceive commands & characters
10160: ' Maximite pins 13 to 16 are D7 to D4. R/W is grounded
10180: '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' ''''
10190: '
10200: '
11000: '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' ''''
11010: ' Initialise the LCD
11020: '
11030: FOR i = 11 TO 16 : SETPIN i, 9 : NEXT i ' set all pins to open collector output and 5 volt
11040: _LCD_byte = &B0011 : GOSUB 13090 : PAUSE 5 ' reset - part of a 3 byte sequence of 0011xxxx to properly reset LCD
11050: _LCD_byte = &B0011 : GOSUB 13090 : PAUSE 5 ' reset
11060: _LCD_byte = &B0011 : GOSUB 13090 : PAUSE 5 ' reset
11070: _LCD_byte = &B0010 : GOSUB 13090 : PAUSE 2 ' 4 bit mode
11080: _LCD_byte = &B00101100 : GOSUB 13000 ' See Function Set in table where = 4 bit, 2 lines,5x10 dot chr format
11090: _LCD_byte = &B00001100 : GOSUB 13000 ' display on, no cursor underline, blink off
11100: _LCD_byte = &B00000110 : GOSUB 13000 ' increment on write, display shift off
11110: _LCD_byte = &B00000001 : GOSUB 13000 ' $01 = clear display
11120: RETURN
11130: '
11140: '
12000: ' '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' ''''
12010: ' send the two lines to the LCD
12020: ' the text is in LCD_Line1$ and LCD_Line2$
12030: '
12040: _LCD_byte = &H80 : GOSUB 13000 ' select the 1st line
12050: FOR _LCD = 1 TO 16
12060: _LCD_byte = ASC(MID$(LCD_Line1$, _LCD, 1))
12065: PRINT "sending ...",MID$(LCD_Line1$, _LCD, 1),"which equals ",_LCD_byte ' this line for diagnostic purposes
12066: PAUSE 50 ' time to view line above
12070: PIN(11) = 1 : GOSUB 13000 ' send the character - sending one character at a time
12080: NEXT _LCD
12085 '
12090: _LCD_byte = &B11000000 : GOSUB 13000 ' select the 2nd line
12100: FOR _LCD = 1 TO 16
12110: _LCD_byte = ASC(MID$(LCD_Line2$, _LCD, 1))
12120: PIN(11) = 1 : GOSUB 13000 ' send the character
12130: NEXT _LCD
12140: RETURN
12150: '
12160: '
13000: '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' ''''
13010: ' Send a byte to the LCD
13020: ' the data to be sent is in _LCD_byte
13030: '
13040: PIN(13) = _LCD_byte AND &B00010000 ' output the 1st 4 bits - this isc LCD D7
13050: PIN(14) = _LCD_byte AND &B00100000 ' output the 1st 4 bits - this isc LCD D6
13060: PIN(15) = _LCD_byte AND &B01000000 ' output the 1st 4 bits - this isc LCD D5
13070: PIN(16) = _LCD_byte AND &B10000000 ' output the 1st 4 bits - this isc LCD D4
13080: PIN(12) = 1 : PIN(12) = 0 ' tell lcd to accept data by driving EN (Enable line) H to L
13090: ' Entry point to send just 4 bits to the LCD
13100: PIN(13) = _LCD_byte AND &B00000001 ' output the 2nd 4 bits
13110: PIN(14) = _LCD_byte AND &B00000010
13120: PIN(15) = _LCD_byte AND &B00000100
13130: PIN(16) = _LCD_byte AND &B00001000
13140: PIN(12) = 1 : PIN(12) = 0 : PIN(11) = 0 ' tell lcd to accept data by driving EN (Enable line) H to L
13150: RETURN

RayB from Perth WA

James_From_Canb

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Joined: 19/06/2011
Location: Australia
Posts: 265

Posted: 01:25pm 03 Jul 2011

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I've modified the original code to use a 4 x 20 LCD screen.
I found the start addresses for the lines by trial-and-error, because I couldn't find them in the specifications. Please let me know if it doesn't work on your 20 x 4.

Let's see if the file upload works....

James

2011-07-03_232346_LCD_4x20.zip

My mind is aglow with whirling, transient nodes of thought careening through a cosmic vapor of invention.

Hedley Lamarr, Blazing Saddles (1974)

stuarts

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Joined: 15/06/2011
Location: Australia
Posts: 199

Posted: 04:16pm 03 Jul 2011

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James, the hitachi 44780 chipset used in these displays typically have 80 bytes of RAM. Just enough to display 4 x 20. Usually you will find the lines start at 0,20,40 and 60 decimal.

I do have one 4 x 40 display. It has 2 44780s which means you have to initialise 2 displays and whether you want to work in the top half of the display or the bottom detirmines which chip select you activate to use the display.

Stuart

Time is nature's way of keeping everything from happening all at once.

James_From_Canb

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Joined: 19/06/2011
Location: Australia
Posts: 265

Posted: 09:28pm 03 Jul 2011

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Thanks Stuart,

Yes, I read that on various sites, but it didn�t work for me if I substituted it into Geoff�s code. I only got the first character printing on the second line, for instance. First line OK, third line OK, nothing at all on the 4th line.

For instance, Geoff uses &B1100 0000 to select the second line. The highest bit (D7) means SET DD RAM Address. The next 7 bits are AC6 down to AC0. So Geoff used 0100 0000 (=64 decimal) to set the second line for the 2 line LCD. Not an even multiple of 20.

So I wrote a little program that used 0 to 127 as start addresses and wrote an X to the screen. The addresses I used in the code are those that allowed a full line of Xs to be written.

BTW, if I set the address to line 1 and write 80 contiguous characters, they fill out each line correctly.

Maybe I did a bad job soldering and shorted out an address line - or maybe it's something weird about my eBay 20x4 LCD panel with blue backlight, which cost under $10 including shipping from China.

Whatever, I put all the constants at the top of the program. If anyone has an LCD panel that works with 0, 20, 40 and 60, just change the values.

I'm looking forward to trying one of those 4x 40 displays. Now if I can just find one for under $10 from eBay....

James

My mind is aglow with whirling, transient nodes of thought careening through a cosmic vapor of invention.

Hedley Lamarr, Blazing Saddles (1974)

Ray B
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Joined: 16/02/2007
Location: Australia
Posts: 219

Posted: 01:44am 04 Jul 2011

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Well done James this publishing of code for others to learn from is what forums are all about and what Bob Devries touched on in an earlier post with him writing an extended MM Basic manual.
What ever happened about the idea of somewhere code could be dumped for others to use?
Must now go on ebay and try and find your 20.4 LCDs....

RayB from Perth WA

Talbit
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Joined: 07/06/2011
Location: Australia
Posts: 210

Posted: 03:00am 04 Jul 2011

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Stuart,
See my post yesterday re the mistake in Geoff's LCD circuit. In your above code, you have changed the remark re the pins at line 10160 but your code is the same. No doubt you've actually run it with your above code. I recon with Geoff's original code AND original circuit, it won't work. I believe the pins should be 13 to 16 are D4 to D7 and Geoff's code unchanged. How have you wired up your 20 X 2 display?
Regards
Talbit

Talbit

rhamer
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Joined: 06/06/2011
Location: Australia
Posts: 174

Posted: 03:15am 04 Jul 2011

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James_From_Canb said I'm looking forward to trying one of those 4x 40 displays. Now if I can just find one for under $10 from eBay....

James

I've got a pile of them, I'll send you one with your order.

Regards

Rohan

Rohan Hamer
HAMFIELD Software & Hardware Solutions

Makers of the Maximite Expander.

http://www.hamfield.com.au

stuarts

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Joined: 15/06/2011
Location: Australia
Posts: 199

Posted: 07:51am 04 Jul 2011

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Talbit, I haven't used any lcd on the maximite yet. I was using the 4x40 a lifetime ago on a microcontroller called the Tiny Tiger. They were quite advanced for their time. It was just a comment on the HD44780 controller and how it maps the display and therefore the limit that they have with displays with more than 80 characters.

Stuart

Time is nature's way of keeping everything from happening all at once.

James_From_Canb

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Joined: 19/06/2011
Location: Australia
Posts: 265

Posted: 08:39am 04 Jul 2011

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I'm back from work - the curse of the Maximite enthusiast.

During lunch I found this link LCD Link. It says something similar to Stuart, and I had read on other sites - that the lines start at 00H, 40H, 20H and 60H. The control byte start with a leading 1 (80H or 128), followed by the address. So I would expect the control byte to be
line 1: 80H + 00H = 80H = 128
line 2: 80H + 40H = C0H = 192
line 3: 80H + 20H = A0H = 160
line 4: 80H + 60H = E0H = 224

but the same site says, under useful commands:
Moves cursor to first address on the left of LINE 1 = 80H = 80H + 00H. Tick
Moves cursor to first address on the left of LINE 2 = C0H = 80H + 40H. Tick
Moves cursor to first address on the left of LINE 3 = 94H = 80H + 14H (20D). ???
Moves cursor to first address on the left of LINE 4 = D4H = 80H + 54H (84D). ???

The author has come up with the same numbers I found for lines 3 and 4, but I have no idea why they work. Anyway, at least it's unlikely I have a solder bridge or similar, so I'm reasonably confident the code is correct. I just don't know why, because lines 3 and 4 are supposed to start from addresses 20H and 60H.

Next on the list: Scrolling text, an LCD_LOCATE function and more constants to define LCD operations.

My mind is aglow with whirling, transient nodes of thought careening through a cosmic vapor of invention.

Hedley Lamarr, Blazing Saddles (1974)

Ray B
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Joined: 16/02/2007
Location: Australia
Posts: 219

Posted: 09:00am 04 Jul 2011

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For another great LCD Interfacing reference don't overlook the PicAxe Manual # 3 pages 31-42 available from http://www.rev-ed.co.uk/docs/picaxe_manual3.pdf.

Speaking of PicAxe don't overlook the new M2 range of controllers with expanded specs
http://www.rev-ed.co.uk/docs/picaxem2.pdf
The hubble 08 now has 2K memory, supports 1800 lines of code with I2C and all of the other hi level instructions for A$5.

When we get serial onto MaxiMite we can progress to MaxiMite driving a PicAxe network either through cable or wireless but that is all 6 months away.

RayB from Perth WA

Ray B
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Joined: 16/02/2007
Location: Australia
Posts: 219

Posted: 09:27am 04 Jul 2011

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LCD Rows/ Columns this should explain

RayB from Perth WA

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