hi guys

i am having some problems getting a graphics lcd display k0108 to interface with a pic 16f887

maye someone can help me here

i am using asembler language as this i am an old timer and dont understand c as well as i dont have any compilers for c so asembly language it is.

here are my problems
1) i seem to be able to reset the display and switch it on when i do this part of the routine i get all the pixels on this is not to much of a problem as i can send a couple of commands to clear the screen so i can turn on the pixels that i want. but according to all the datasheets i have been able to get hld of on the internet if you do a reset then the display should return to position 0. i would think that it should aslo clear the screen.

this is not happening what appears to be happening is that the glcd has some type of memory in it so when a reset is done it goes back to the place it already is at and does not clear the display.

2) also there seems to be a problem with the adresses as if i point to position 1 page 0 z=0 then the display goes to seven pixels across, so if i put in a y adress of 58 then it starts at the beginging of the line.

3) also if i try to write to cs1 and cs2 together then the lcd does not respond
to any changes after the first write i gather therefore you have to access the one then the other.


please could someone look at my code and then let me know where i am going wrong if at all

Attached Files

GLCDTEST.asm (9.2 KB, 35 views)

 

You appear to be doing something strange with the Enable line. The Enable line should be low all the time and pulsed high to read/write to the display.

These are specific to my hardware but should give you some idea.
The WaitNotBusy routine is a little convoluted as I test both displays dependant on if the CS lines are high. Sorry about the lack of comments.

HTH

Mike.

 

On the GLCD I owned, there is no RESET command one can send to the GLCD. When powered up, the GLCD enters a RESET state and user can check if the reset operation has finished via reading the STATUS byte and testing a bit in it.

The reset operation will not clear what was displayed on the LCD. In fact, on mine the previous data still remains even if I remove the main power for a few seconds and power it up again. Therefore user must be pro-active to clear the display by writing to every pixel to switch it off. This can be easily done via a loop.

With regard to the pixel addressing, you need to check the datasheet. I offer an image to help you along in understanding the addressing scheme.

You simply cannot write to both GLCD Controllers at the same time, similar to one cannot write to two memory locations at once.

Attached Images

GLCD.gif (29.3 KB, 28 views)

__________________
L.Chung

 

I just looked at the data sheet and reset only sets Z=0 not X & Y and doesn't clear the display.
One other thing, in the above data sheet it does not mention the fact that to read data from the display, you have to do a dummy read first.

Mike.

 

Oh yes you can. My clear screen routine above does exactly that.

You cannot read from both at the same time, hence my convoluted TestNotBusy routine.

Mike.

 

Thanks Guys I Am Going To Give These A Try And Will Get Back To You

 

Thanks Mike. That's very useful to know. Can save half the time in clearing the display.

__________________
L.Chung

 

thanks pommie

seems that i was reading the datasheet incorrectly as after you gave me that code and i repaired mine it works.

thanks if you would like to see the finished code i will post it it might be interesting for someone else????

thanks

 

If anyone is interested I use two 'LS164's to interface to my KS0108 display so I can drive it with two I/O pins only. You can't read the diaplay status but sometimes that is not as important as saving pins I/O so you can use the display with say, a 12F675.

 

So, you add two extra chips rather than use a bigger pic chip.

Mike.

 

It appears to be some kind of PIC users disease. I dislike glue logic unless I have a good reason for it.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

Basically it's 30 year old thinking - adding extra chips to make a micro-processor useable. The whole point of a micro-controller is that it's mainly a single chip solution - although there are obvious occasions when 'glue' chips may be useful, but starting off with a chip you know is far too small isn't really one of them.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

There are times when offloading some functions onto 'glue' hardware is a valid/justifiable design option.

Might actually be better in some cases than the "throw a bigger PIC at the problem" disease (grin)...

Mike

 

Your glue logic seems to be a pic!!

Mike.

 

Glue logic is a very common use for a PIC!.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk