Hi,
Does anyone know if it would be possible to drive a flexible LCD display with this board? I've got a project that this would be almost perfect for, but I need a graphics display. Something like:
http://iteadstudio.com/store/index.php? ... 45emg2f6r0
or
http://iteadstudio.com/store/index.php? ... 45emg2f6r0
which both use an 8 bit data bus.

I saw the project on the wiki that used a serial lcd, that really wouldn't be fast/flexible enough I don't think. I'd really like to get the lcd set up in such a way that it can be driven as a standard framebuffer display, so I use standard libraries / api's in our software to output to it.

Can the GPIO pins (or similar interface) be memory mapped such that I could use DMA to copy data from ram over an 8 bit interface? Or even if I had to bit bang them, how quick can they be driven?

Thanks,
Andrew

I guess if you could configure the Ethernet Ports for use as GPIO's as well as the UART Pins you should be able to control this display with the aid of 8 Bit latches. That of course would further decrease your data transfer rate to the display.
The hardware I2C on the carambola should theoretically be fast enough to get a decent framerate out of a serial display though. So you could pick up a fast microcontroller to handle the conversion I2C->parallel.
A third option would be to get a decent USB enabled microcontroller (like the STM32F4) and build some kind of USB graphics card that can drive the parallel display.

Of course all those solutions require a lot of linux driver programming knowledge.

I've been looking into it a little more myself and I'm wondering if I write a custom driver I could possibly use gpio 9-16 via the PIO registers to transfer my 8 bit data, leaving I2C and SPI available for other system uses.
I would also need some of the higher gpio pins for control lines to the lcd, but it looks like it'd work. I don't need hardware uarts at all.

The big question would be how quickly I could shift 8 bits of data repeatedly on the second byte of the 24 bit long GPIO23_00_DATA register.

Alternately, how quick can the SPI interface be run? I could possibly just use that for graphics if I could either find myself a decently priced spi lcd, or make an interface with a cpld / fpga.

Thanks,
Andrew

The HArdware SPI speed was discussed somewhere else in this Forum. You'll also find the information in the Datasheet of the CPU.
From what I remember the SPI clock is generated (via a variable division factor) from the System Clock, which is master_clock/3.
I think the default SPI clock is system_clock/128 ... But don't take my word for it, search the forum or have a quick look at the datasheet, the truth is out there. ^^

However, hardware SPI should be fast enough to drive a LCD like that resolution with a decent frame rate.

I'm actually working on a similar issue: I'm trying to get a 320x240 display with a 16-bit parallel interface to work on the Carambola. I think I should be able to do it with 3 4094s and the SPI-port. My target is to get Doom running on a Carambola this weekend

In hindsight I should have thought of that myself, I'm using a string of them (7 of them) in a current project at work to give a massive parallel breakout over SPI. they certainly work well for me there. They can usually be clocked quite high too, over 20MHz iirc.

So you're planning on making it a proper video driver, that's great. Are you doing it as a basic framebuffer device, aka http://www.linux-fbdev.org/HOWTO/4.html ?

Wow, great work and a neat result.
Now I wish I had some hardware to help out, this could turn it into a great little unit for me. Might have to buy me one, and a similar lcd.

Andrew