advice on 240 x64 displays

[longpole001]

Hi Guys ,
I have been looking at using a 240 x 64 graphic LCD , in a design , and had some question of those that may have used them before.

1. I have need to show large digits on the display to 1/100 of sec and counting up as a timer , is it likly to be problem if the interface is spi/ seriel for pic running A software or hardware interface at 32mhz to the display
2. I have to also go and do other things of about 1- 50 ms during the time that the display is not being updated probably interrupt driven , will the display likly to stop during this time


regards

Sheldon

[HenrikOlsson]

That is almost impossible to say when you don't even give us a model number for the display in question so we can look at it, how it works, what controller it has etc.
But lets say it's a monochrome, 1bit per pixel, serial interface. You have 15360 pixels on the screen and you want to update the screen 100 (!) times per second, that's an average bitrate of around 1.5M or 192000bytes per second - not counting the overhead of any control bytes.

The MSSP module can send data at a rate FOsc/4 so at 32MHz the maximum bitrate is 8M but that doesn't give you ANY room to actually fetch the data and feed it to the MSSP module. If you run it at FOsc/16 it'll give you 2Mbit per second and you'll have a couple of instructions left over to do something with while the MSSP module sends the byte.

Now, why on earth do you need 100 updates per second? Just because you have a timer resolving 1/100seconds doesn't mean you have to update the display that often. If you update it 20 times per second the average bit rate drops to 300kbit which I think is more manageable. But then you have to generate the bitmap data....

Obviously, if this is an intelligent display with built in fonts etc it's a different story but how do we know that when you don't give us any details....

/Henrik.

[longpole001]

hi hendric ,

i love to give details , but i am just searching the net on posable lcd modules at the moment , raised the good point on if the display need to show the 100/sec digit until it stops , else it blur anyway .
this part of the design stage for the controller part of the project

i have been looking at few options , my requirements are

1. display in direct sunlight - reflective is best option but some do offer good use in direct without backlight even if backlight is there
2. large digits - 25mm high prefered or close for display of the timer with 6- 8 digits needed with dots
3. 6ock view angle
4. device run on batteries - so try and use less power is best
5. need to display other alphanumeric data as well and looking at adding a specific display 16x 2 or 20 x4 line for this requirement

options when taking these item into consideration come up with
a. Using a glass lcd for time count , and alphanumeric for other requirments
b. large 40 x2 alphanumeric with a special large font for digits timer , still need addtional alphanumric for other function display
c. a graphic display for digits and if large enough combine 2 display requirements - custom fonts required constant updating timing for other items maybe an issue

Problems.
1, Glass display require a driver to be made and PCB and are often only availalbe in large production runs in quanity of 500 or more , else u may not get them , but some searching will turn up few here , buy in 100 lots only
2. combined cost of glass LCD display and driver , pcb will exceed the cost of 5.5 " graphic display 240 x64 which can display a large digits.
3. Alphanumeric display are great and you can make some large custom fonts to use 2 or 4 lines , but the fonts look avg and gaps in the chars are seen , you wont Ever find any that have the same size or even close as glass lcd for the cost , but they do
have drivers on board
4. the larger the display the more power it uses
5. cost , cost cost , i need to make this with all requirement for about $100usd , and good design v cost is driving me nuts

sorry vented

Cheers

Sheldon

[HenrikOlsson]

Hi,
Have you seen the SmartGLCD from MikroE? Currently out of stock but seems to fit the bill @99USD.
I've got one and I started writing PBP code for it a year or so ago, didn't have any particular use for it so the project kind of stalled after a while.

/Henrik.

[longpole001]

looks very nice , have looked at using a tablet , but use in direct sun was an issue , too bad they dont do a nice case for it as well for that price , have found simular displays so at about $60usd , so $100 is nice

Hendri what ur thought on updating a large display with a timer and still have time to do other items on the interupt even with this nice display ??? in the end the same problems are there ??

[longpole001]

also battery power would be an issue and addtiona cost for such a nice item

[mark_s]

This might work, 240x64 serial glcd $27usd watch the video looks pretty good for the money.

On ebay search "240x64"

http://www.ebay.com/itm/Serial-UART-...item3a7b862984

[longpole001]

Hey Mark ,

yes got some of those on the way for a test , this guys has added is own brew of SPI interface to the unit with some custom coded commanded for graphic usage in the pic chip interface , he is very shy when it comes to real details on timing of the interface for the spi , hold times etc , think he just never did the timing charts.

i am hoping that using a graphic display for a fast counter , will refresh quick enough not to jump , and adding a spi to the display wont slow it up to be an issue

strange that a simple glass lcd or digit led is often a easier for large digit display usage still

[mark_s]

Hi Longpole

He has another video on Youtube comparing speed with other glcd's. I am pretty sure his display is controlled by a T6963 which is an old standard. Then he is using a PIC or AVR to receive serial, store fonts and drive the T6963 parallel port.

Here's the speed video. He gives the full refresh times - fastest 10ms refresh

[longpole001]

mmm interesting test i do note that the larger display is not using the entire area during the test

[longpole001]

another thing i found was that it would be nice to get make graphic menu etc , for a display using this , but basic is not supported
http://www.easygui.com/xfaq.asp?mk=28&sc=9&me=12&ex=no

[longpole001]

but this may work
http://www.mikroe.com/visualglcd/specification/#tabnav