DOGM are a COG (chip on glass) style of LCD which is an attractive
alternative to the standard alphanumeric display. The space behind
the display and its transparency, as well as the functionality of the
controller, make options available to the user not possible with self-
contained modules
This page is here to demonstrate initialisation with a PIC, as much of
the material out there purporting to do this is confused, misleading
or just wrong
Manufacturer's site
http://www.lcd-module.com/products/dog.html
At this time, April 2011, DOGM LCDs are in stock at Mouser
Unlit, daylight
lit, diffused white LEDs
Tested on PIC 18F2520, 39.3216MHz (9.8304MHz PLL) LCD Vdd = 5V, 8-bit parallel mode ;macros line1 macro movlw 0x00+0x80 ;line 1, column 0 call writec endm line2 macro movlw 0x40+0x80 ;line 2, column 0 call writec endm display macro var ;load TBLPTR with string address movlw upper(var) movwf tblptru movlw high(var) movwf tblptrh movlw low(var) movwf tblptrl tblrd*+ call get_txt ;get characters, print endm ;PortC 0-7 - LCD data #define rs latb,1 ;RS #define rw latb,2 ;R/W #define en latb,3 ;Enable ;example definitions function1 = 0x39 function2 = 0x38 bias = 0x1c power = 0x52 follower = 0x69 contrast = 0x74 disp_on = 0x0c disp_off = 0x08 clear = 0x01 entry = 0x06 crsr_on = 0x0f crsr_off = 0x0c ddram = 0x80 cgram = 0x40 strings = 0x400 ;display string storage address bcf en bcf rw bcf rs call ms100 ;> 18ms delay call lcd_init display m1 ;show Line1 text line2 display m2 ;show Line2 text ;================================================ ; Initialise LCD screen (8-bit, 5V) ;================================================ ;The 162 initialisation sequence found on page 7 of ;Electronic Assembly's product guide ; ;http://www.lcd-module.de/eng/pdf/doma/dog-me.pdf http://www.lcd-module.de/eng/pdf/doma/dog-me.pdf ;is substantially correct, although it doesn't contain ;other required information found in the ST7036 datasheet ; ;The initialisation sequences and code examples in ;the ST7036 datasheet, however, are just plain rubbish ; ;(IMVHO) ; ;You should have it though ; ;http://www.lcd-module.com/eng/pdf/zubehoer/st7036.pdf http://www.lcd-module.com/eng/pdf/zubehoer/st7036.pdf lcd_init movlw function1 ;must use this sequence call writec movlw power call writec movlw contrast call writec movlw bias call writec movlw follower call writec movlw function2 call writec movlw disp_on call writec movlw clear call writec call ms01 call ms01 movlw entry call writec return ;================================================ writec bcf rs bcf rw bsf en movwf d_temp ;temp if W over-written by delay call us100 ;> 96us delay movfw d_temp movwf latc bcf en call us100 ;> 78us delay return writed bsf rs bcf rw bsf en movwf latc bcf en call us30 ;> 15us delay return ;================================================ ; Fetch string for LCD ;================================================ ; LCD text strings get_txt movfw tablat ;get characters until btfsc wreg,7 ;W > 0x7f (ie FF terminator) return call writed ;print W tblrd*+ bra get_txt ;================================================ ; LCD text strings ;================================================ org strings m1 db "Gettin' it done",0xff m2 db "WWW.PICLIST.COM",0xff
In this analyser shot of the initialisation sequence, note that Busy (D7)
is useless
for interrogation. As soon as R/W goes low, Busy goes high, and remains
there.
writec has two 100us delays that must be done. The completion time for
writed
is quite short, around 20us, so a wait delay would probably be practical
for most
software. If not, the user will have to make sure enough time has elapsed
before
attempting to write more data
So far I've not been able to get a double-height display that looks like
the one
in the datasheet. As far as I can tell, there is no central line of pixels
to fill the
gap. All 16 rows are accounted for. If this is true, double height would
be of
limited use. joecolquitt@clear.net.nz please if you find any missing pixels
or have
the command values to display double height as seen in the datasheet. The
double
height datasheet illustration, by the way, uses an undocumented "S" and is
not
italicised, so make of that what you will
lit, red cellophane
lit, green wine bottle
lit, printed paper insert (transparency would be much better)
lit, pink/purple cellophane
backlight jig, using dimmable 3 x 1W white LEDs and opalescent acrylic
This PCB can be wired to suit any of the 6 options in the dog-me.pdf. It's
the
pattern I've used for toner transfer. Make sure that the solder bridge gaps
are
open after etching, or amend the diagram to suit your hard-wired
configuration
EA have an Eagle library, ea.lbr, in their Downloads section
The cutout can be removed if you want the lighting to be further back,
which
will help the light spread and improve evenness
Note that COG displays are fragile and trying to remove one from a PCB
could
cause it to be damaged
Copied with permission from:
http://home.clear.net.nz/pages/joecolquitt/dogm_lcd.html
See also:
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Ashley Roll has put together a really nice little unit here. Leave off the MAX232 and keep these handy for the few times you need true RS232! |
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