adafruit 2.8″ capacitive tft screen

Today’s review is on the small TFT touchscreen for the Raspberry Pi computer. At $45, it’s not the cheapest screen you could add onto a single-board computer but the capacitive touchscreen and the four accompanying tactile pushbuttons along the side make it worth the extra money, especially if you’re adding it to a 3D printer for the sake of control.

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TFT

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Installation

As usual, the Adafruit documentation was more than adequate to get this done. They provide an installation script which makes the process easy.

Observations

The touchscreen works wonderfully, much better than the typical/cheaper resistive TFT that we’re most familiar with.

I’ll need to determine which GPIO pins those four pushbuttons go to. It will be nice to use those in some sort of interface.

I reviewed both the OctoPrint-TFT and TouchUI interfaces for OctoPrint on this. I’m not convinced that either are a perfect fit, given the size of the screen. Both required the Desktop to be installed on Raspbian. In the case of TouchUI, it required the use of a local browser on the Pi (Chromium) but I was able to get this to go into the full screen mode.

Other than as a control interface for a 3D printer, I’m not quite sure what projects would be a good fit for this. The timelapse rail kit would be good for this setup, perhaps. It’s a little bulky for a cryptocurrency cold wallet. It would probably make a good streaming music player, given the positioning of those buttons.

Adafruit makes some very attractive enclosures for this, unfortunately they’re out of stock at the moment.

  • Size: 2.8″ (board matches form factor of Raspberry Pi 3B)
  • Screen dimensions: 50mm x 69mm
  • PCB dimensions: 56mm x 85mm
  • Brand: Adafruit
  • Model: 2423
  • Name: PiTFT Plus 320×240 2.8″ TFT + Capacitive Touchscreen
  • Cost: $45
  • Resolution: 320×240
  • Touchscreen type: capacitive
  • Feature: extra 40-pin header underneath board
  • Feature: four tactile pushbuttons

glacier

Earlier today, I created a Raspberry Pi Trezor (cold wallet) for cryptocurrency using that cool Adafruit 1.3″ OLED bonnet.

PiTrezor

It seems to reasonably work from a fork of the original code. It presents itself to the Trezor Bridge software and to your workstation as a slave USB device. I suppose you could think of the entire thing as a smart USB thumb drive, if you will.

The code image is smaller than you’d normally expect (50MB). I’ll get in there and take it apart later from a software standpoint.

Notes:

  • The interface is beautiful on the small screen with attractive fonts and functional animations.
  • I don’t love websites which only work with a single browser. In this case, it’s Google Chrome of course and it was necessary to install that for Trezor to work at all.
  • The standard screen assumes that the buttons are positioned below it, not so for the Adafruit hat. So you just have to guess that the furthest button equals the right-most button and it all works out.
  • The GPIO pin layout of the OLED bonnet is different from the native Trezor device so of course, the bootloader upgrade routine doesn’t work as expected. It will be necessary to recompile and reload the image in order for this to work. I’ll have to review all that to see how it affects me to I don’t love anything in the cryptospace which can’t keep up to the current state of the art.
  • Having the micro USB cable sticking out of the side of the Pi just seems awkward so I’ll work up a serial connection to the GPIO pins with a USB plug tail and incorporate all this into a slick-looking case.
  • I don’t think I enjoy the website interface for selecting other cryptocurrencies. I think I like the KeepKey version of this better, to be honest.
  • Although Trezor suggests they’re compatible with other currencies, they seem to only be able to do Ethereum via a third-party. The hand-off to that third-party provider was about as ugly as it gets and I aborted. You shouldn’t have to create multiple accounts to simple store a wallet.
  • Unless I gain more confidence with all this, I won’t be putting any money in the wallet but it’s an interesting exercise.

adafruit oled display

Other than importing gadgets, Adafruit sometimes also designs them. Today’s review is for their cool 1.3″ OLED display for the Raspberry Pi computer. It appears to fit exactly the top of the Raspberry Pi Zero WH (the one with the included header).

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At $22.50, the hat is about twice the cost of the computer itself. The 128×64 display is enough for most projects, I’d guess.

I’m thinking that I’ll use this one to develop a cold wallet for cryptocurrency.

The hat (“bonnet”) includes a joystick with four positions and a pushbutton as well as two stand-alone pushbuttons on the right. It comes with good support on the Python side of things. If you’re like me and prefer Node JS, then you’ll be doing a lot of research on this one.

The interface is I2C. The device identifier is SSD1306. The example software includes text- and image-based Python and a bit of an animation of text.

In case you’re interested, I’ve written a tutorial for getting this setup.

3d cover for the pi noir camera

Using the (included) industrial-grade Autodesk Fusion 360 software, I was able to design a part for my Robo C2 printer. It’s a cover and mount for the Raspberry Pi NoIR v2 camera (8MP resolution @ $27). I picked up several cheap suction cups (@ $0.99) from Ace Hardware yesterday and used a digital caliper to carefully measure the distances all around. I’ll sand it a little to make it smooth; the photos below is what it looks like after removing the raft and supports (throw-away extras to make everything print correctly). The jaggies inside the suction cup slot I’ll leave since they’ll grip tightly. I’ll likely also keep some of the jaggies in the fitting between lid and base for the same reason.

I’ll still need to receive the longer cable from Adafruit for this to work so I haven’t snapped down the parts firmly yet. In the meantime, I might create a ribbon clip with a second suction cup (editing the money clip from an earlier post).

If you’d like the STL files for the part now, let me know and I can shoot you the URL for those but I’ll eventually write up a step-by-step tutorial on the full upgrade to adding the video feed capability.

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100posts

too much fun

My two packages arrived today at the post office so I just hauled in all the loot from this earlier post in which I’ve purchased some new toys.

Raspberry Pi Zero W

The photos from their website don’t really describe how truly small this computer is now. They’ve somehow managed to stack the RAM on top of the microprocessor to save space. As I’ve apparently ordered the wrong video adapter cable, I’ve got a trip over to Best Buy Frye’s Electronics this evening so that I can sort that one out. I need a female HDMI to DVI, in other words. Otherwise, I’m still pretty stoked. Since there’s only one micro-USB I think I’ll temporarily need a small USB hub while I’m at it.

PiZero

NeoPixel Ring

This arrived as well, all four of the segments but it was lost on me that I’ll need to solder each of them together. Fortunately, I have a soldering iron here somewhere. :looks around: I’m certain of it.

COZIR CO2 Sensor with RH/Temp

And in the other relatively BIG package is the relatively small sensor package. No wonder they charged me $21.88 to ship this to me. Seriously, it weighs about an ounce.

And it looks like I’ll need a 2×5 jumper to attach this over to the Raspi, with a solder-able header for that, too.

Update 1

Alright, I’m back from Frye’s with a handful of stuff and I’m back in business. The video adapter allows me to see what’s coming out of the Raspberry Pi Zero W and the micro-USB hub allows me to hook up a keyboard and mouse to talk to it locally. A first install with the Raspbian Jessie Lite image resulted in a terminal-only configuration (I must have been in a hurry and didn’t read the differences on their page) so a second install of Raspbian Jessie with Pixel was just what it wanted: a full desktop experience.  If I get some time this weekend I’ll try to have it talk to either the sensor or the light ring.

Update 2

I just managed to solder together the NeoPixel ring. Due to the size of the electrical pads on the ends of these, I’d suggest that this falls into the catagory of advanced soldering and not to be taken on by the average person.

NeoPixel
These are not my lovely hands.

Additionally, I’d say that this feels a bit fragile in the area of the soldering joints between each quarter-circle. I’m going to suggest that anyone who incorporates one of these into their project needs to seriously think about ways of making this more stable/reliable since the soldering joints between them are tenuously-small.  (Imagine three distinct electrical connections across the tiny width of this thing.)

What I also found is that there isn’t anywhere to clamp a hemostat for soldering these jumpers since the LEDs run all the way to the end where the connections should go.

I did add an inline resistor as Adafruit suggested to lower the input voltage or perhaps to lower start-up voltage spikes.

I managed to re-purpose a nice external 5V switching power supply that should drive all the LEDs nicely. It was left over from the supercomputer project when I swapped in a USB-based charger instead for that. Amazingly, Adafruit suggests that those 60 LEDs need a whopping 3.6A of power to drive them. I’m guessing that reality is more like 1A but I’ll play this safe. Per Adafruit’s suggestion I included a 1000 µF electrolytic capacitor across the output voltage to protect the NeoPixels.

VGD-60

So I’m prepped to do a final test of the NeoPixel ring for power and functionality on a standard Raspberry Pi 3 rig (since it sports an actual header). Once I’ve coded a test and verified that it works then I’ll take the soldering iron to the Raspberry Pi Zero W and wire it in with a quick-connect.

headerwire

I’ve now got the Raspberry Pi Zero W booting with just the power adapter. Note that you can rename its hostname, toggle on the VNC Server, adjust the default screen resolution to your liking and then—in the Finder program in OS X—open up a remote session to its Desktop with vnc://pi@hostname.local, for example. Or, toggle on the SSH Server and connect from a Terminal session with ssh pi@hostname.local.

Have I mentioned how awesome it is to have a fully-functioning computer for $10 (plus $6 for the micro SD)?

And now the power supply is completed and wired to the NeoPixel ring. Everything’s set for 5V DC in at the moment but I may try to adjust the input voltage down to 3.3V later for technical reasons. (The NeoPixels are designed for the Arduino and its output data voltage is 5V whereas the Raspberry Pi is only 3.3V. By adjusting the input voltage down then it makes a 3.3V data line look bigger than it is. There are other tricks like adding a 3V-to-5V data inverter chip but I’d like to avoid that one if possible.)

PowerSupply

Update 3

I’ve smoke-tested the power supply/ring combination and it’s looking good. To make things easier for this step, I’ve now setup a surrogate Raspberry Pi 3 for testing things but since I only had a leftover 4GB microSD, I was forced to use the no-desktop “Lite” Jessie version of Raspbian. But that’s now ready and I’ll likely have some time this weekend to do a basic blink test.