Avr / arduino with a tft lcd screen - Page 1
Forum section: electronics / projects

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 16, 2013, 05:15:36 pm
content: What sort of frame rate would a tft screen such as this ebay item: 360565808398Be on a standard 16MHz arduino? And would it be improved if i moved to an atmel avr that runs at a higher frequency?

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 16, 2013, 05:26:18 pm
content: Just realised its in the wrong section :/. Any chance of moving it?

author: mariush
author_rank: Super Contributor
timestamp: June 16, 2013, 05:54:25 pm
content: Read the datasheet of the controller used:http://www.adafruit.com/datasheets/ILI9325.pdfYou have there all you need to know... latencies, frequencies etc

author: Harvs
author_rank: Super Contributor
timestamp: June 17, 2013, 04:25:32 am
content: Quote from: carbon dude oxide on June 16, 2013, 05:15:36 pmI 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?

author: Stonent
author_rank: Super Contributor
timestamp: June 17, 2013, 07:28:52 am
content: It can be done, or at least you can drive a VGA Monitor or a TV with sound.

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 17, 2013, 08:53:36 am
content: 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

author: Harvs
author_rank: Super Contributor
timestamp: June 17, 2013, 12:52:53 pm
content: 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.

author: airiclenz
author_rank: Contributor
timestamp: June 17, 2013, 01:18:04 pm
content: This might be a good resource for you (this guy pretty much goes to the limits):http://andybrown.me.uk/wk/Good luck!

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 17, 2013, 01:53:42 pm
content: 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....

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 17, 2013, 02:22:25 pm
content: 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

author: mariush
author_rank: Super Contributor
timestamp: June 17, 2013, 02:43:08 pm
content: 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.

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 17, 2013, 06:19:23 pm
content: 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?

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 17, 2013, 06:23:02 pm
content: Yea thats what i meant. Sorry i have not had time o rea threw the data sheet (revising foran exam tomorrow)

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 18, 2013, 10:57:07 am
content: 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?