Avr / arduino with a tft lcd screen

[carbon dude oxide]

What sort of frame rate would a tft screen such as this ebay item: 360565808398
Be on a standard 16MHz arduino? And would it be improved if i moved to an atmel avr that runs at a higher frequency?

[carbon dude oxide]

Just realised its in the wrong section :/. Any chance of moving it?

[mariush]

Read the datasheet of the controller used:  http://www.adafruit.com/datasheets/ILI9325.pdf

You have there all you need to know... latencies, frequencies etc

[Harvs]

What sort of frame rate would a tft screen such as this ebay item: 360565808398
Be on a standard 16MHz arduino? And would it be improved if i moved to an atmel avr that runs at a higher frequency?

I assume you're referring to what frame update rate could the AVR produce.  Driving full colour displays is always a difficult task for uC's where you need to draw things quickly.  You've got 76.8k pixels to draw with probably multiple bytes per pixel (e.g. 16bit colour is common.)

So the question is how do you intend on using it?  Are you just going to pump frame data from flash memory directly onto the display?  Or do you actually intend on drawing stuff pixel by pixel?  Are you making a gui or a picture viewer?

[Stonent]

It can be done, or at least you can drive a VGA Monitor or a TV with sound.

[carbon dude oxide]

Im would like to make a gui which would be loading information from an sd card to view it with text overlay (i belive you can do that).

Ive got a ps/2 keyboard attached to my avr currently which i can type words ect onto it so i would like to words to come up onto the screen if possible

[Harvs]

Well you can do it, sure.  But it may not be as quick as you'd like (and you don't have a DMA to preload sections out of the SDCARD like on a larger uC.)

It's not exactly all that expensive, so why not just give it a go.  It's a reasonable learning experience anyway.

[airiclenz]

This might be a good resource for you (this guy pretty much goes to the limits):

http://andybrown.me.uk/wk/

Good luck!

[Mechatrommer]

type "arduino screen" in youtube you'll find many variation and performance. the keypoint is not processor speed alone, but the method, code or algorithm used or what application you want it to do. you can do shit with GHz processor driving this lcd module... few simple examples....

[carbon dude oxide]

whould the screen have a faster refresh rate if i changed to a 32 bit avr with a higher frequency? or is it limeted to the speed of the data bus between it? (that if the data bus is not being hindered by the avr already

[mariush]

Oh man, lcd screens don't have a "refresh rate" ... once a pixel is lit it stays lit, it's not like CRTs.

The datasheet should tell you how often it can go update pixels with new information, it's related to duty cycle and other things which are specified in the datasheet.

Read (or at least browse) the datasheet I linked  to in a post above, the controller supports i2c, spi, rgb, i think even s-video or composite.

I don't think you  have to send full screens to the LCD so there's no issue of refresh rate,  i think it supports basic commands like line drawing and individual pixels. If it doesn't, you're only limited by the bandwidth of your SPI or i2c bus or whatever you use.

I don't know how fast an Arduino is, but it may have only a 400 Khz i2c bus, or a 1.7 Mhz SPI bus, or something like that... if you only work with a 32x32 icon on the display maybe you can get 60 updates a second, maybe less.
 

[Mechatrommer]

agree, read the datasheet for maximum data rate, from there you can calculate the minimum time to redraw a screen which i believe what you mean refresh rate?

[carbon dude oxide]

Yea thats what i meant. Sorry i have not had time o rea threw the data sheet (revising foran exam tomorrow)

[carbon dude oxide]

Ab i see, i didnt realise you could update pixles at a time instead of having to reload the whole screen.

Another quick question for this project that i am doing, would it be better to either:

Stick with my PS/2 keyboard shield and library to read the keyboard (for arduino) or would it be better to get an AVR with device/host usb capabilitys to read it off of a usb keyboard?