Raspberry Pi gains $35 HAT-based touchscreen
Jul 28, 2015 — by Eric Brown 14,813 views
[Updated: July 29] — 4D Systems and Newark Element14 launched a 2.4-inch, QVGA “4DPi-24-HAT” resistive touchscreen for the Pi for $35, said to be the first to use a “full” HAT design.
Last October, the Raspberry Pi Foundation’s Eben Upton briefly demonstrated an upcoming official Raspberry Pi touchscreen. It’s unclear whether that 7-inch, VGA capacitive touchscreen is still on course, but in the meantime, there are a variety of RPi touchscreen options to choose from. The latest is a 4DPi-24-HAT screen from 4D Systems and distributor Newark Element14. It’s claimed to be the first to offer full compatibility with the Pi’s HAT (Hardware Attached on Top) add-on card standard.
4DPi-24-HAT screen (left) and PCB
(click images to enlarge)
HAT, which has been used in devices such as Pi Supply’s Papirus E-paper display, enables the Pi SBC to automatically configure its GPIO signals and drivers for use with external devices. This is said to ease installation for users, and make life easier for developers, as well.
As a reader informed us, this is not actually the first Pi touchscreen with a HAT interface. The Adafruit PiTFT 2.4″ HAT TFT Touchscreen does indeed support a HAT connection. Yet, 4D Systems appears to have an argument for using the qualifier “fully.”
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The 2.4-inch, 320 x 240-pixel PiTFT kit, which sells for $35, requires some soldering, which does not appear to be necessary with the 4D Systems screen. Specifically, the Adafruit page says: “Some light soldering is required to attach the 2×20 GPIO header to the HAT but it’s fast and easy for anyone with a soldering iron and solder. Alternatively, you can use a stacking type header instead if you’d like to plug a 2×20 GPIO cable on top” (See farther below for some other Pi touchscreen options from Adafruit and others.)
4DPi-24-HAT in color, and being installed on the Pi
(click images to enlarge)
Like the 2.4-inch PiTFT display, the similarly $35 4DPi-24-HAT is on the low end of the touchscreen spectrum. Its 2.4-inch screen has 320 x 240-pixel resolution, and it uses 4-wire resistive, rather than the more sensitive capacitive touch technology. The full-color touchscreen supports a typical video framerate of 25 frames per second, “which can be increased with kernel compression,” says 4D Systems. (The manual, which is perhaps older, says 17fps.)
4DPi-24-HAT dimensions
(click image to enlarge)
The 30-gram, 65 x 56.5 x 14.4mm screen displays the primary output of the Raspberry Pi A+, B+, or the latest Pi 2 Model B. The device requires no external power supply, and it runs directly off the Raspberry Pi’s 40-pin header.
The 4DPi-24-HAT is optimized for Raspbian Linux, and communicates with the Pi via a 48MHz SPI connection. The screen’s backlight can be switched on or off using an on-board jumper, or dimmed using PWM controls. An on-board EEPROM is said to enable quick device recognition by the Raspberry Pi.
Other Raspberry Pi touchscreens include the 4D Systems 4Dpi-32 and $69 4Dpi-35, which has a 3.5-inch, 480 x 320 resistive screen. Additional options for small touchscreens include the 2.8-inch, 320 x 240 PiTFT resistive display sold by Adafruit for $35. There are also a few 7-inch touchscreens, including the 800 x 480 Tontec 7″ screen selling for $52 on Amazon, and the SainSmart 7 Inch screen going for $50.
Further information
The 4DPi-24-HAT is now available for $34.95 from Newark element14 in North America, Farnell Element14 in Europe, and Element14 across Asia Pacific. You can also buy it from the 4D Systems Online Store.
AdaFruit has been selling PiTFT HATS for a while now. They seems to have HAT versions of both the 2.4 and 2.2 inch displays, at least. Maybe 4D systems should rethink that whole “first to use the hat design” thing…
funny I thought the Pi attachment were called tins… as in pie tins…
Connection is over SPI?!? Oh come on! You got a high speed DSI port and you’re not using it?!?
That requires licensing a chip from Toshiba (I think it’s Toshiba) to talk to that part of the Pi hardware. The chip itself was semi-recently developed and the first product slated to use it is the official Raspberry Pi Foundation LCD screen, mentioned in the article. Other people can make products using the chip and the DSI connector, but it will most likely cost more than $35.
The GPIO/SPI displays have been around forever simply because they’re cheap. You can get these displays for $15 on ebay (less if you don’t mind soldering), and for displaying basic data (status monitor, camera view finder, or even a screen for a game emulator) they fit the bill quite nicely. The big lure of these screens is that they are small, because you can buy a 7 inch LCD with an HDMI interface for around $45.
In other words, yes, you can use the DSI port, but it’s not economical to do so at this time. It’s also not economical to use this Element 14 LCD screen for $35, which is a total rip off.
Adafruit was not the first company to make such LCD screens. Others in the community were selling fully assembled GPIO screens like this for a long time before Adafruit or Element 14 did a screen. This is not new. This is Element 14 trying to boost sales with an overpriced screen. You can get the same thing or better for about $15 on ebay or various other sites.
You’d think for the price they’d have shelled out for capacitive touch. The relevant films aren’t that much more expensive, nor is the control chip.
QVGA “4DPi-24-HAT” resistive touchscreen for the Pi for $35, said to be the first to use a HAT design. Last October, the Raspberry Pi Foundation’s Eben Upton briefly demonstrated an upcoming official Raspberry Pi touchscreen.