10" to 14" displays in MCU applications, Cortex-M3 etc - Possible? - Page 1
Forum section: electronics / projects

author: mindThomas
author_rank: Contributor
timestamp: February 07, 2012, 05:22:10 pm
content: Dear EDABoard members.I have been searching the internet for a while looking for a display solution to connect to an MCU but with bigger sizes than 7".I have previously done LCD/TFT projects using the SSD1963 controller chip from Solomon to drive a 7" display with a resolution of 800x480 pixels.Though now my requirement in size (NOT NECESSARILY RESOLUTION) have become bigger, so I have been trying hard to find another solution.I have been working with the following solution ideas but I would like you to comment on them or even come up with other options.Get a larger display, 10"-14", but with the same resolution, 800x480, so it would be possible to drive it with the SSD1963Find another display controller capable of driving the standard 10"-14" displays with resolutions around 1024x768Find a larger display with integrated display controller or with a supported display controller module next to itMake our own controller chip using an FPGA and some SRAM for driving the LCD lines directlyWhat do you think? Please come up with other ideas if possibleThank you in advance.Best RegardsThomas Jespersen

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 07, 2012, 05:59:58 pm
content: A problem is that larger displays tend to have different interfaces, like LVDS, due to the higher data rate. they don't seem to make large low-res displays.Low-level interface aside, one easy solution might be to do pixel-doubling, at least horizontally.Another possibility may be to generate an output at VGA or similar, and feed into a panel that has a standard monitor interface, which will rescale as necessary for the panel - you'd want to choose a resolution which is an exact divisor of the panel resolution to avoid resampling artefacts.FPGA+SRAM/SDRAM is probably going to be the most flexible solution long-term as you will be able to easily change formats depending on requirements and panel availability. Some FPGAs (e.g. Xilinx Spartan-6) can output DVI directly, and so should be able to drive LVDS-input (panel link) displays & DVI/HDMI monitors without additional hardware.

author: gregariz
author_rank: Frequent Contributor
timestamp: February 07, 2012, 07:05:11 pm
content: Video can be a complete PITA. I'm not an expert but these are my recent findings with the FPGA LVDS option. a) It can be extremely noisy in terms of emissions. b). The quality of LVDS waveforms are often complete shite (maintaining balance seems to be pretty difficult). And because of this I would recommend you buffer the lines with both a buffer chip and provide for placement of one of those soic style low pass filters in order to try to clean up the lines before they hit the connectors. Use a quality sealed connector with a quality impedance matched cable with 200 ohm pairs. My personal preference would be to use an off the shelf display solution in conjuntion with a proven reference design (ie OMAP includes a DVI-D interface as used ont he Beagleboard) or an off the shelf singleboard computer with integrated display solution.

author: mindThomas
author_rank: Contributor
timestamp: February 07, 2012, 07:16:32 pm
content: Well, it might not be necessary to use LVDS as we could probably find the display we require with a digital 24-bit interface with VSync and HSync etc.Though the problem lies in whether we could find a specific LCD controller for the case or we should make our own.Or maybe even if we could find a processor with the display controller already inside - a bit like the LPC2478, though it is not powerfull enough for 1024x768 I think.Or maybe an ARM9 like the LPC3xxx series, though that might also be overkill as we are not going to run any OS on top of it.

author: erupter
author_rank: Contributor
timestamp: February 07, 2012, 10:10:30 pm
content: Besides the interface itself, a major "problem" that relegates high-res displays to powerful processors is the amount of pure data required.At 1024x768x32bit with double buffering (not nearly a ground-breaking tech) you're looking at 6.2 MegaBytes (!!!) of raw data.That's AFTER every rendering/rasterization/whatever is done!In the case of a 60Hz refresh rate, you're looking at 120MB/s of processed data!That's why every half-decent thing that has to relate with a monitor has a video-card of some sort nowadays.So that most of the calcs are done by the highly optimized architecture, you essentially load drivers that abstract as much as possibile.That's impossible in any strictly called MCU.It gets possible when processors start having external memory busses, so I think the ARM v7 at least.Dunno specifically as I'm mainly a Microchip guy, but seeing how the M3 is positioned in the market, I doubt it can support hires displays.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 07, 2012, 10:14:35 pm
content: Quote from: erupter on February 07, 2012, 10:10:30 pmThe NXP LPC18xx Cortex-M3 parts may be worth a look - there are some that have onboard LCD controller.

author: mindThomas
author_rank: Contributor
timestamp: February 07, 2012, 10:36:21 pm
content: Quote from: mikeselectricstuff on February 07, 2012, 10:14:35 pmYeah, I have been looking at that.Or maybe also the LPC178x ->http://ics.nxp.com/support/microcontrollers/lcd/