parallel lcd questions
PFloyd36069
Posts: 135
hi,
is there any way to make a parallel lcd work through through the vga plug on the demoboard. the lcd needs 7 pins but the vga plug has only 5 useable pins. also dan miller's parallel lcd object doesnt seem to work right with my lcd. I just get a bunch of strange looking characters. i changed the code a bit to make it work with the 8 accessible i/o's on the demo board.
thanks,
bryan
is there any way to make a parallel lcd work through through the vga plug on the demoboard. the lcd needs 7 pins but the vga plug has only 5 useable pins. also dan miller's parallel lcd object doesnt seem to work right with my lcd. I just get a bunch of strange looking characters. i changed the code a bit to make it work with the 8 accessible i/o's on the demo board.
thanks,
bryan
Comments
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Timothy D. Swieter, E.I.
www.brilldea.com·- Prop Blade, LED Painter, RGB LEDs, uOLED-IOC, eProto fo SunSPOT, BitScope
www.sxmicro.com - a blog·exploring the SX micro
www.tdswieter.com
between the plug-pins and IO-Pins of the propeller there are 240 and 470 ohm-resistors. You can try it but the resistors have an influence on the signals.
It depends on your LCD if this will work directly. If the LCD has 5V it will be good anyway to use voltageshifters from prop 3.3V to LCD 5V
You cannot drive an LCD with VGA-signals created by the videohardware of the propeller. But of course you CAN use any of the 32 IO-Pins for any purpose
If anybody does not believe this: take an LED and connect it between VGA-Pin and ground and start a small prg that makes the IO-pin switch between
low and high. The LED will blink. Of course 240 ohm and even 470 ohm is more than nescessary for a 20mA-LED but it will blink.
best regards
Stefan
Post Edited (StefanL38) : 8/7/2008 6:58:19 PM GMT
Another possibility is "E" needs to be pulled low with a 4.7K resistor. The Pull-Down resistor isn't showed in to many diagrams, but I have had to use it on all my LCD's. Also I don't think you will need the data line resistors unless you are using RW to write data back to the Propeller.
I've made a 3 wire lcd (not counting the power) using that chip. It also looks like the VGA has a 5V output on pin 9 so your LCD should be fine with that.
As you can see from my picture there are only 3 purple wires from the header.
If you are interested then I could try to get you going on it. I will try later to see if I can make a quick VGA to 10pin header cable and try to get the lcd working on the demo or proto board .
Pete
'' parallel lcd driver '' for using a HD44780 based 4 x 20 parallel lcd '' dan miller 23 july 2006 '' {{ 10k 5v +--+ +?----?--------------------------------+ ¦ ¦ +------+ ¦??+ ¦ ¦ ?grd nibble ops msb first ? ?--¦• ¦ 10 13 15 ¦ ¦ grd ¦ ¦ ¦ 11 ¦ 9 12 ¦ 14 ¦ ¦ ??-+ 100 ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ? ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ?--+ +--¦--¦--¦--¦--¦--¦--¦--¦--¦--¦--¦--¦--¦--¦--¦--¦--+ 1 ¦ • • • • • • • • • • • • • • • • ¦ 16 LCD v v v r r e D D D D D D D D V V s c l s / n 0 1 2 3 4 5 6 7 B B s c c w + - }} con _clkmode = xtal1 + pll16x ' use crystal x 16 _xinfreq = 5_000_000 ' ------------------------------------------------------------------------- ' IO Pins ' ------------------------------------------------------------------------- ' LCD bus is 12..15 E = [b]0[/b] ' Enable Bit RW = [b]1[/b] ' Read Write Bit RS = [b]2[/b] ' Register Select Bit obj delay : "timing" bs2 : "BS2_Functions" var ' ------------------------------------------------------------------------- ' Variables ' ------------------------------------------------------------------------- byte char ' Character To Send To LCD byte inst ' Instuction To Send To LCD byte index[noparse][[/noparse]2] ' Character Pointer {{ usage - uncomment the 'tester located below to run and test this module by itself' otherwise, with the line tester commented out, use start thusly --> term : "parallel_lcd" term.start repeat term.out($00) ' clear screen term.str(string("Dan's Sawmill ")) term.pos(0,2) ' second line, pos 0 term.str(string("Sawmill head height")) display_height(0,3) ' third line , pos 0 term.out($22) ' the " char term.pos(0,4) ' fourth line, pos 0 term.str(string("2nd key for more")) ( a example from one of my programs ) }} pub Start | temp waitcnt(clkfreq * 1 + cnt) ' let lcd come up dira[noparse][[/noparse][b]0[/b]..[b]6[/b]] := %11111111 ' Make Output. outa[noparse][[/noparse]RS] := 0 outa[noparse][[/noparse]RW] := 0 Init_Lcd tester ' code to check module by itselfPost Edited (PFloyd36069) : 8/10/2008 1:52:32 AM GMT