Finally, An Official Display For The Raspberry Pi

Yes, finally, and after years of work and countless people complaining on forums, there is a proper, official display for the Raspberry Pi.

It’s a 7-inch display, 800 x 480 pixel resolution, 24-bit color, and has 10-point multitouch. Drivers for the display are already available with a simple call of sudo apt-get update, and the display itself is available at Newark, the Pi Store (sold out) and Element14. There’s even a case available, and a stand ready to be sent off to a 3D printer.

As for why it took so long for the Raspberry Pi foundation to introduce an official display for the Pi, the answer should not be surprising for any engineer. It’s EMC, or electromagnetic compliance. The DPI (Display Parallel Interface) for the Pi, presented on the expansion header and used by the GertVGA adapter allows any Pi to drive two displays at 1920 x 1024, 60FPS. This DPI interface is an electrical nightmare that spews RF interference everywhere it goes.

raspberry-pi-touchscreen-thumbThe new display could have used the DSI (Display Serial Interface) adapter, or the small connector on the Pi that is not the camera connector. DSI displays are purpose-built for specific devices, though, and aren’t something that would or should be used in a device that will be manufactured for years to come. The best solution, and the design the Raspberry Pi foundation chose to go with, is a DPI display and an adapter that converts the Pi’s DSI output to something the display can understand.

The solution the Pi foundation eventually settled on is an adapter board that converts the DSI bus to DPI signalling. This of course requires an extra PCB, and the Foundation provided mounting holes so a Pi can connect directly to it.

While this is the first display to make use of the DSI interface, it will assuredly not be the last. The Pi Foundation has given us a way to use the DSI connector to drive cheap DPI displays. While the 800×480 resolution of the official display may be a bit small, there will undoubtedly be a few hardcore tinkerers out there that will take this adapter board and repurpose it for larger displays.

[Alex Eames] got his hands on the Pi Display a few weeks ago, you can check out his introductory video below.

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Using Cheap Displays With The Raspberry Pi

The Raspberry Pi B+ has a native VGA connection. Sure, it’s hidden away in binary blobs and device trees, and you need to wire up the GPIO pins just right, but it’s possible to connect a VGA monitor to a Raspi B+ natively. For the brave, smart, or foolish, this means you can also drive raw DPI displays. [Robert] had a few of these dirt cheap displays sitting around and decided to give the entire thing a go. It worked, and he’s written down how to do it.

One of the chip architects for the Raspberry Pi, [Gert van Loo], was exceedingly clever when designing the Pi. There’s a parallel interface in the chip that, when combined with a few dozen resistors, can drive a VGA display in addition to the HDMI display. Screens with a Display Parallel Interface are actually pretty similar to what the VGA spec calls for. The problem is, hardly any of this is documented for the Raspberry Pi, and finding it means trawling through forums.

[Robert]’s example circuit uses a 5″ display from Adafruit, a 40-pin breakout, and a bunch of prototyping wires. Setup requires grabbing a cut down version of the device tree used for the Raspi VGA breakout board, setting the output format, rgb order, and aspect ratio of the display, and wiring everything up.

What’s interesting here is that [Robert] reproduced this project from scratch, and found that any display with a 40-pin DPI connector will work with the Raspi, provided you have a datasheet. That’s pretty cool; these displays can be cheap, and since we don’t yet have a proper DSI display for the Pi, this will have to do for now.

Video below of [Robert]’s inspiration for this build, [Ladyada].

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