An award-winning LCD with an Arduino built-in (using only 2 pins) | Hacker News Reader

An award-winning LCD with an Arduino built-in (using only 2 pins)

blog.arduino.cc

68 pointsleonvonblut39 comments

I know people are saying this is a bit steeply prices, but I think this is perfect. I've been looking at the various options and they typically all require three components- the touchscreen/lcd itself, a controller board of some sort, and then the Arduino itself. Then you have to actually put it all together, and as people have mentioned you end up with a lot more than two pins being used.

This one at Adafruit costs $40, uses five or six pins, is smaller and doesn't have the Arduino built in.

It's a nice project. I've purchased stuff from EarthLCD before and they're a good group. Those complaining about the price probably have never tried tooling their own kapton/copper flex circuit.

"This one" being this one- http://www.adafruit.com/products/1651

On a side note, I like how the product is presented by two young girls. Is this intended for educational purposes?

I can't tell whether you're being a feminazi or just a creep. Either way, stop it.

(S)He is pointing out that the presentation is done by two people who are usually not associated with technology and development (they are young and female) as a positive example.

He then posits that this is to show the educational possibilities.

Any negative connotations are coming from your mind, not theirs.

Agreed, it's clearly scripted but when she moves onto presenting the project you can tell she actually built it or has the understanding of a maker

I love that the target audience is advertising the product.

That's probably why, but I only made it about 30 seconds into the first video before I had to turn it off. Maybe I'm in the minority, but listening to kids present anything really frustrates me.

> 320 x 240 Resolution

Aside from the fact that's for an arduino, which probably mean very low power available, does anybody knows why all those hobbyist LCD are so low in term of resolution?

It seem impossible to find something higher than VGA on mouser or even Alibaba, much less a reasonably priced HD screen. Where are all those glorious smartphone screen?

(I'm talking about small screen, but even larger one are not that much better)

I'd never though I'd say this, but 320x240 may be enough resolution. Especially at 3.5 inches and for hobbyist projects. All the projects I can think of to use this are for simple notification-style display and maybe one finger interaction.

A DIY smartphone seem something where having a good screen would be a plus, or everything photo where color accuracy and resolution are important.

I was looking to make an EVF[1] for my DSLR a while ago for example.

[1] http://en.wikipedia.org/wiki/Electronic_viewfinder

I use my Android as an EVF / remote controller for my 550d. It's pretty damn useful and you can pick up a second hand phone for basically nothing.

Never heard of that, that seem interesting, would you happen to have a link with more information?

https://play.google.com/store/apps/details?id=eu.chainfire.d... is what I use. USB OTG cable to USB Mini. Does the job fine on a Nexus 5.

http://www.mikroe.com/add-on-boards/display/

Mikroelectronika have some interesting displays but they're all little.

Could you point out where are the HD screen? I tried to look, but all of them seem to be 320x240 or lower, which is what I was complaining about :).

I'm guessing these are all "left over" or superseded feature phone components. I've got a few from a couple of years back that are explicitly sold as "Nokia screens" and all the library code makes it pretty clear they're Nokia 3xxx series phone parts.

The "hobbyist LCD" market doesn't get purpose designed components - not at the volumes and prices hobbyists are prepared/capable of buying. We get to re-use end-of-life components or buy the end-of-reel scraps from current product manufacture. (which is fine by me. I love being able to buy accurate 9DOF IMUs, but I sure as hell don't want to order them in reels of 10,000 un-hand-solderable SMD parts)

The glorious smartphone screens are in smartphones, which cost a lot more than 90 USD.

Not really, the Nokia Lumia 520 for example is at $50/70£, and had an IPS screen with a 480x800 resolution, I never saw such a screen sold for hobbyist.

http://en.wikipedia.org/wiki/Nokia_Lumia_520

this guy is right. even an overpriced oem replacement for mobiles, with all the extra stuff attached to the board, runs under the $100 range.

just paid $98 for a noteII screen and digitizer combo. its full hd i think.

so, stop sugar coating. lcd and digitizers are cheap. this is either low volume hobbyist market or pure greedy.

and looking at how other things are priced in those sites, like a small roll of wire for $20, id bet it is greedy.

It's low volume hobbyist market, obviously. And that has overheads. Don't call people 'greedy' for selling things at greater than the BOM cost.

LVDS panels aren't uncommon. In fact, I believe (but not checked) there should be lots of them being sold as replacement parts for notebooks and tablets.

For example, relatively recently there was a post on HN about RaspberryPi-based DIY tablet. It had this link for LCD panel: http://www.chalk-elec.com/?page_id=1280#!/~/product/category.... The store page now says it's discontinued, though, but this was meant just as an example and I'm too lazy to search for a better offers, sorry. :)

Although, those are probably of no use with AVR microcontrollers directly, without a display controller like http://blog.tkjelectronics.dk/2012/10/lvds-display-controlle... or http://hackaday.com/2009/12/12/fpga-driver-for-psp-screen/. Phone LCDs just have it already and panels don't.

Calculate the amount of memory required for a 320x240 256 color display: 320*240 = 76.8KB. An Arduino only has 2KB of RAM, so an external controller has to do basically all of the drawing opereations. This controller has its own SRAM framebuffer.

Once you get larger than 640x480, it becomes impractical to have the framebuffer in SRAM. DRAM is the obvious choice, but increases system cost and complexity sharply and so you first see it on "application processors", e.g. Cortex-A7 and up.

Also, DRAM PCB routing is very complex, and the connection from the display controller / system-on-chip to display is also critical.

Well, you'll find the glorious smartphone screens are sold as replacement screens for smartphones.

But of course, smartphones tend to have an LCD controller on the SoC, so you just get a raw LCD parallel interface. That means the LCD has a tiny connector with dozens of wires. Hobbyists are often enough scared of soldering SMD parts, they won't try to solder that .4mm pitch connector.

Then you realise that even for 800x600 @ 60Hz you need a pixel clock of around 36 MHz, so you probably need a hardware controller, you can't really get away with DMA and/or bit banging. Since you have an external controller, you can't do any of the memory efficient drawing like Nintendo NES or sifteo[0], so you'll need external buffer memory, probably at least 2 MB to fit two (16 bit colour) frames for double buffering.

As the resolution grows, pixel clock frequency and memory size requirements grow quite quickly. Soon enough you get limited by the bandwidth between your MCU and controller, by limitations of parallel interfaces and have to switch to LVDS and so on.

Most of these issues become much less relevant if a (even small) company wants to design, manufacture and sell something like this. But I'm not sure there's a demand. For most projects a small screen (with a controller chip and available for cheap because it was designed and manufactured at scale for older phones) works well enough (and you can get away with using a wimpy 8 bit MCU). If you need a larger screen, it's probably cheaper to get a low cost single board computer and a computer monitor. Economies of scale and all that.

[0] https://www.adafruit.com/blog/2012/12/05/how-we-built-a-supe...

Thanks for the explanation.

That's something I wondered, taking a smartphone screen, but it seem pretty daunting, indeed. Such a shame in a way.

It looks cool, but the price is a bit steep. You can get a touchscreen LCD from Adafruit at $39.95 (http://www.adafruit.com/products/1651). You still need to buy an Arduino, but they're cheaper than $45,-. I've bought Chinese Uno V2's for less than $15 a piece.

The advantage of their integrated LCD and Arduino is that it would only use 2 pins instead of the 6-7 that would be occupied by the shield you linked. This would allow you to connect other shields and have more room for add-ons. I agree that $89 is steep though, hopefully that price can come down as more are made.

I don't understand how this board only "uses 2 pins". The schematic shows the ezLCD component still uses 7 pins for I/O. Using the SPI bus requires 4 pins and the other 3 are presumably for the touchscreen sensing. The board still has the full Uno footprint, so you could connect other stuff to those pins at the same time, but you couldn't do anything with them while driving the LCD.

Dallas 1-wire? Haven't looked at the schematic or anything else, but that's an example of an interface that just requires 2 connections - signal and ground.

That's not what this uses.

There is a PIC24f that does all the graphics processing, and the arduino talks to it through serial. the spi connection is used to program the atmel . the other connections are optional for use like a interrupt on touch .

The arLCD is 3.5", whereas the $39.95 from Adafruit is 2.8". That still shouldn't account for the price difference though.

You could do it cheaper but you would run out of code space quick taking care of the graphics. on the arLCD the onboard PIC Micro takes care of all the graphics. You just tell it where to put a widget and it takes care of the rest .

Okay, how do they run that color picker sketch with only 2 KB of RAM available on the Uno? I tried to do some string parsing and it failed at 200 byte-long strings due to lack of memory, how can they show an entire picture composed of thousands of pixels?

Could be a more powerful ARM Cortex, rather than the insanely out-dated Atmel chips. If anyone ever makes a 5V ARM processor Atmel will be finished.

Also I'm going to rant about Arduino for a bit: Yes it's very simple and easy to get started with, but their API documentation is bad, and the IDE is objectively and irreparably awful and has not really improved since it was first released. Making things even worse they don't provide a decent way to integrate it into other IDEs because lots of the build logic is tied up in the IDE.

I'm all for supporting small business that create hardware, especially open source (heck, I'm working on some stuff myself), but they must make an effort to make their products affordable. I can buy a 3.2" touchscreen LCD for $12 in single quantities[0], shipped locally in the UK. The BOM for an Arduino is somewhere around $10 in single quantities. Their selling point about only using 2 pins? Yeah, shift registers or i2c I/O expanders are so fancy...

[0] http://www.ebay.co.uk/itm/3-2-TFT-LCD-Display-Module-Touch-P...

Does anyone have any idea of what it will cost? I can't wait to get my hands on one of these.

following the link, it seems to available for $89.00

It's a bit steep at $89.

http://earthmake.com/product/arlcd/

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