OLI (Open LCD Interface) a design for using LCD's with Arduino and Raspberry Pie

Great project.

Are you going to sell your circuit cards or make the designs available?

I plan to make the project open source, just dont want to release the designs yet, there are minor bugs still on the PCB's and also I want to get some feedback from the community to release a tool that can be used by many makers.

@Douglas: if you are interested on a prototype PCB you can let me know since I had to order a full lot and have just used 2 or 3

I've given up checking out hackaday.io. Whenever any project interests me, it invariably doesn't have schematics or sufficient detail to replicate..

I have a question

Why another interface when there are already so many SPI displays for both these platforms already, and if you don't want SPI then there are displays that are intelligent and connected via fast serial like the Nextion Displays

There are more issues here with the different actual display protocol differences than the communications differences. Ie each chip manufacturer uses a different set of registers, different setup etc. SPI r I2C or DVI etc is not the issue here.

Adding a layer of abstraction will slow it down if not done right. With boards like the Nextions, the user is only concerned with the active content once the display has been graphically designed and this is the current way of designing most HMI displays these days

So back to my original question... WHY ?

I am all for the learning exercise etc and a great educational tool but there is a lot of competition you will have to overcome with this.

Well, you are focusing more on only one aspect of the design and not looking the big picture. The idea of this project is to break the lines of the LCD to be driven by any display controller in 3 parts:

(1)Microcontroller/Dev Board -----> (2)LCD controller ---> (3)TTL LCD

For the example of this thread I used (2) with a chip with SPI to connect the arduino to the LCD and a chip with HDMI to connect the Raspberry Pi. If you find a LCD controller with I2C or UART you could still use the LCD and the dev board of your choice, and I think this is the difference, it is modular so you choose how to use your LCD rather than the manufacturer of the dev-board/LCD controller.

I made this project for solving a personal problem I faced when I needed to display basic measurements from a temperature sensor to a 5 inch LCD. The project was changing from when it begin and I did not want to have an LCD-shield for every dev board I own and also to use the same LCD with development boards with HDMI video signal such as the Raspberry Pi, PC Duino, BeagleBone, etc. 

So the message here is to have a flexible design where depending on the requirements of your project you select the elements to use (dev board, graphics controller) and keep the same LCD, you have the choice. It may be the solution you need maybe not, the competition is not the point, this is just another tool.

Small microcontrollers often have more computing power than early Windows PCs, but they typically are not designed to have a full user interface. It is always a struggle to add a graphical display to these small computers at a price that is comparable to the cost of the micrcontoller. I often run into a requirement to display an image or lots of text on a small microcontroller and it is great to see more options appearing that address these types of reqirements.

The HDMI module in Joe's system is a useful interface while we wait for more small displays to have built-in HDMI decoders at a reasonable price.

I really like the SPI interface module - all microcontrollers have SPI interfaces. While there are some canned solutions with SPI interfaces, this system allows you to find nice low-cost LCDs with features and form factors optimised for your application and make them useful without incurring a large development cost and associated schedule delays.