Re: Microcontroller with QVGA or VGA LCD controller

Ulf Samuelsson wrote:
"David Brown" <david@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> skrev i meddelandet news:47c56945$0$14989$8404b019@xxxxxxxxxxxxxxxxxx
donald wrote:
David Brown wrote:
Does anyone have any recommendations for microcontrollers with LCD controllers for QVGA (320x240) or full VGA (640x480) displays?

I've found a few large devices (a ColdFire v3 device, and a number of ARM9's from Atmel) that have LCD controllers supporting much larger screens, but these are pretty big and fast microcontrollers, with large pin counts and needing sizeable external memories.

I'm hoping to find something a bit smaller and cheaper, and easier to work with.

Stand-alone LCD controllers would be an alternative, if such a thing exists these days.
Wouldn't a smaller controller be slow in up-dating the display ??

640x480 monochrome display = 307200 pixels; /8 = 38400 bytes.

I don't think any smaller controller can address that large of a frame buffer memory.

And color could be 4, 8 or 16 times larger.

Something to consider.

I'm expecting to use a 32-bit controller, with a large enough external databus (or large enough internal memory if I'm lucky) to handle the memory needed. I'm not going to need to update the display very quickly (it will mainly be text messages - no video or anything). I expect something in the class of 40-100 MHz ARM7 or ColdFire v2 to be appropriate. So "smaller and cheaper" here is relative to the 200+ MHz devices I found in my first searches.

If you use VGA resolution, you need 36 MB / second bandwidth
from your memory system, just to do refresh.
On top of that you have overhead for CAS/RAS precharge.
The LCD refresh would eat up significant part of the bandwidth
so your ARM7 would slow down to crawl.


That would be for a full VGA, 40 Hz refresh, 24-bit colour. We won't need that much - I am not even sure if we are going for full VGA instead of QVGA (at the moment, we are considering the advantages and disadvantages of both), and we won't need that level of colour fidelity.

Also, the processor won't be doing much work anyway - all it will have to do is write to the screen on occasion.

The AT91SAM9261 has 160 kB of memory on chip, and
there is no conflict whatsoever if you do display refresh

The AT91SAM9263 has a dual bus system so you can realisticly
use up to 800 x 600.


These two are devices I've already found, and are definitely under consideration (I haven't used ARM's before, but we use a lot of AVR devices from Atmel - so they are an obvious candidate as a supplier). They are greatly overdimensioned in power and features for what we really need - but we are still looking at possible options at the moment.

To give you an idea, the prototype system today is running with an AVR controlling the card and a 32x140x1-bit graphics display with its own attached LCD controller. We want to have a larger and nicer screen, with support for colour and simple graphics. It's even possible that with a LCD controller such as the Epson devices mentioned in this thread, we'd use an AVR to control the screen (with an external serial flash to hold logo bitmaps).

Both of them are of course in BGA, but you can get CPU modules
from various sources with an ARM9 with LCD support.
* www.ronetix.ch
* www.iotech.dk
* www.mechatronicbrick.dk


We are not looking at ready-made modules - we have no problem designing and producing cards using devices such as the AT91SAM9 chips. It's just that a card using a 200-300 pin bga 200+ MHz processor and matching memory is going to be a lot more expensive to design and produce than one using a 140-pin TQFP 50+ MHz processor.

mvh.,

David



You could also look at the AVR32 Gateway. (ATNGW100)
Dirt cheap and good Linux support.


.

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