Category Archives: portables

PortablePy: The clamshell micropython computer.

I admit: I love how home computers from the 80ies were booting up in no time. I’ve been trying to optimise the boot up time for Raspberry Pis for some time but I don’t get very far. I’m also fascinated by baremetal implementations where hardware is used for a single purpose and also works on an instant. Micropython is a nice idea inbetween as it is a “high level language” and still runs without too much overhead on very small resources.

Another thing that I’m dreaming of is to be able to write software on the go using a minimal dedicated device. My prrevious attempts comprise:

  • The StickPi (super small Pi Zero with an epaper display and no keyboard for ssh access from a notebook, no battery)
  • The PocketPi (battery powered Pi Zero, 800×480 4in Hyperpixel screen incl a small keyboard)
  • Last week’s PsionPi (battery powered Pi 3a+, Psion 5 Series keyboard incl Arduino keyboard controller and a 7in 800×480 screen)
  • And a yet unpublished 5in screen slate design.

All these are Raspberry Pis in different formfactors. When the Adafruit PyPortal Titano was released, I was immediately in love as it comprises a lot of nice hardware and a 3.5in 320×480 screen that I also had evaluated for the PocketPi.

I also recently came across the hardware line of the M5Stack and their super-small and cheap I2C QWERTY keyboard caught my eye. The keyboard itself is also using an Arduino to read the key-matrix and translate the key presses to externally digestable code. So, this is my third Arduino-controlled keyboard (the recent mechanical keyboard and last week’s PsionPi). The PyPortal also has I2C connections, so let’s try it out:

So the first thing wanted to try out is to connect the two and see if I would get use the keyboard to enter text without a host computer or a USB keyboard. The keyboard is available at 0x5f and you just need to translate the keycodes to letters, certainly you need to translate delete, backspace and return keys to the right “actions” on screen, which kind of results in a minimalistic text editor:

Next thing was to design a case. I never ventured into hinge design, so I wanted to keep it as simple as possible just to get started and to see whether writing code is fun or not. So I started with a slate design:

Actually, the Casio pocket calculator is a clamshell design already, but my beloved Nokia E61 is a good sparring partner in terms of design. So the black base plate is a 125x100mm design which is kind of nice, it wouldn’t get much smaller than this. I got bored with the slate immediately when it finished printing…

On the other hand, what was really a logical next step in terms of form factor was the clam shell design and when I had an old Gameboy Advance SP in my hand, I felt that I need this nice sound when closing and I wanted to have a computer like this. Back to Tinkercad:

Now the baseplate has 100x80mm and the hinge is working really well. I also added magnets on all corners to keep the states stable but they are not strong enough and take up valuable space.

Just for fun, I pulled out my old screen from the earlier PocketPi iterations:

To make this usable, you’d need to add the Pi Zero underneath and power both with a battery plus connect them somehow (not via Wifi 😀 ).

Next it was time to design the power source. This time I didn’t stick with the Adafruit powerboost, I think it is too expensive and it gets fairly hot. I had a couple of cheaper but larger charger boards in a drawer, so I decided to give them a go. To save height and space, I removed the USB plug:

To save height, I also removes the plugs from the pyportal and wired the power cable directly, following the wiring scheme from Adafruit:

Finally, I also removed the plug from the M5Stack keyboard and soldered the cable directly:

I had to modify a couple of places of the original case design and cut out the plugs for USB-C / pyportal, the power switch and the micro-USB charging port, then it was time to fit the power circuit:

Finally, the keyboard is added using a double-sided tape:

And now the little darling in action:

I wrote a little file lister in python as well as a minimalistic python editor. The problem at the moment is that you can’t write to the on-board flash when hooked up to a host using USB-C. Need to check out now whether it works when the device is battery powered. Stay tuned!

UPDATE: I just polished the case design to actually close properly and removed the magnet holders to give the innards enough space. Files are published on Thingiverse now.

PsionPi

There’s certainly an emotional connection to EPOC, the precursor of Symbian OS that was running the high end devices of NOKIA a decade ago. EPOC was initially developed by PSION who kind of pioneered mobile computing (at least here in Europe) with decent keyboards.

Whenever you research about mobile computing all aficiandos praise the quality of the PSION keyboards. Especially the 5 Series are great – so I heard.

But when you look at the device, there is so much love to detail and passion in the design, for example see the hinge:

Actually, I want to build a little computer to write Python programs on the go. My experience with my previous, smaller design, the PocketPi, was that it is actually to small (keyboard and screenwise) to really write code and think about it.

The PSION keyboard is really nice and the 6inch screen is kind of nice, too. There’s even a Python port for this granddad. But I decided to build my own little device, so a Raspberry Pi would be the right computing platform.

Recently, some new displays are available on the market that save the whole HDMI cables and possible additional screen controller boards. These connect directly via a flat cable to the onboard DSI screen interface of Raspberry Pis. This saves a lot of space an height.

You see the USB and HDMI plugs on the left of the 7in screen, missing on the lower screens, these have the flat cable plugs on the board on the right hand side. So for this build, I used the 7in DSI screen that also includes capacitive touch (60€, 800×480 resolution). Both, display and touch functionality are supported by the OS out of the box.

Finally, I also bought a series 5 keyboard on ebay because I wasn’t able to slaughter the functional one that I bought before. There is a guy who tried to fit a Raspberry Pi into the original series 5 case, but he didn’t get very far. What he achieved however, is to design a little PCB containing an Arduino 32U4 (Leonardo compatible) that translates the keyboard’s signals to a USB-HID keyboard profile. It’s about 40€ (adding to the 90€ I paid for the keyboard and the screen).

USB keyboard adapter for Psion Series 5 keyboards 1

Finally I chose the Raspberry Pi 3a+ that has runs on a 1.4Ghz quadcore ARM and includes Wifi and Bluetooth. I love that device because it doesn’t have to many plugs (like LAN or quad-USB like the Pi4), so it’s flat and light. It also includes the DSI port while the Pi Zero W doesn’t.

So this is the final “build” (or rather “composition”, I used a gaffer tape to attac the keyboard to the screen):

So, while the screen itself is about 10mm thick, the Pi 3a adds another 20mm, which is totally unacceptable, esp compared to the Series 5 original 25mm. The screen incl the screw holes is about 120mm, while the keyboard is about 75mm. The Pi 3a+ has 55mm, so if I design a case, maybe I’d move the Pi to the keyboard and would get a floor of 130mm plus case walls. Not sure yet. Probably will also research a different screen, with OLED these are much thinner and lighter.

Software wise, I had to flash the keyboard with an Arduino script provided by the controller board guy on Tindie. That was easy, but it doesn’t support QMK like the pancake 40% mechanical keyboard I built last week. Doesn’t matter, the mapping is easy enough to change in the source code.

Finally, firing up the system and now the EPOC OS. For the first test, I used the emulation running in the browser. On a PC it boots like in a second, on the Pi 3a+ it takes about five minutes, so this is not an option. But see here:

Finally, the EPOC emulator is part of the MAME emulator package, that might be the next step.

Towards a lighter kickstand for my Lenovo Ideapad Duet

This is my first Chromebook and I really love it as it’s ARM driven, has Android support and runs Linux in a VM. The only thing I don’t like is the original kickstand that comes with it as it weighs 240g.

So I ordered this 46g foldable tablet stand and removed the lower lip that usually holds the tablet in place. For the chrombook I need a direct connection to the keyboard that is a broad cloth-like connection to the tablet part.

As this is an experiment, I added “power strips” to it, which is a two-sided glue tape that you can remove easily without leaving stains behind.

Finally, I placed it in the middle of the tablet part:

And voilá, this is how it looks like:

I may design something similar in 3d with even flatter angles and more rounded edges when folded so that I can put it into a bag without the risk of tangling.

PocketPi!

PocketPi in its current incarnation.

TL;DR: 14x11cm portable Raspberry Pi Zero W with 3000mAh Adafruit powerboost 1000, Hyperpixel 4inch display, a keyboard and a4 port USB hub. Scroll down for videos, STL files, shopping list.

I always want to be able to carry a little computer around that reduces the outside distractions, like no email, ideally no browser, no messaging, etc. Actually, I enjoy the “silence” that I have with the Raspberry Pis. They allow me to focus on writing software for robots and the like.

Sometimes, you want to code on the go. My second shot in that direction is the StickPi, a little computer without battery but with an e-paper display and a couple of buttons. I actually keep using it, it’s my most used self designed computer.

My first shot hasn’t been published yet: the SlatePi. It is a 5inch computer with a small keyboard and a 4000mA battery, but it seems to be to large for every day use.

So I did another computer: today’s PocketPi. It is the symbiosis of the first two: portable but still a full keybard and a battery included.

It all started with the idea to build a Pi Zero and a display into my favorite mobile keyboard:

I wanted to replace the mousepad with that display.

So at some time, I started to decompose that keyboard to understand how much space is there to actually fit in a Pi Zero W, battery and the display.

the decomposed keyboard and already cut off left part of the PCB and softkeys.

I quickly learned that a) the inclusion of the driver for a ST7735 1.8inch display is cumbersome and the resolution might actually not be nice for really working with it (128×160), it may be better suited for a retroPi machine.

So I decided to use another display that I had at home already which is a 3.5inch display for the Pi (without HDMI) and some more decent 480×320 resolution.

[I also removed the original battery plug and the keyboard’s switch to reduce height.]

However, I didn’t want to increase the size of the device by the height of the diplay and thus decided that I don’t need the left (media-related) buttons of the keyboard:

Another thing was to ideally keep the height of the original keyboard which is about 12mm, but looking at the standard plugs of GPIO displays, it became clear that I need to apply some tricks:

plug deprived display, pi with a plug

I soldered the rails of a DIP plug to the pi, took away the whole plug from the display cutting off the pins to a bare minimum.

great height reduction.

I also decided that I wanted to have a full size HDMI out so I bought shorter and more flexible cables than I had at home and dismantled them:

decomposing an HDMI cable reduces weight and increases flexibility.

Finally, i also wanted to add a decent non-OTG USB to the machine as OTG adaptors simply SUCK.

Different USB hubs to select from.

I actually went with a little board that included the OTG “logic” already and had one USB on the side to actually keep the keyboard receiver and stay within the devices case.

before dcomposing the USB 4 port hub.

During the journey, I decided to upgrade to the final Hyperpixel 4 inch display, with a decent 800×480 resolution. The advantage is the little increased size (4mm) compared to my 3.5inch before plus it can be switched off via GPIO. So this is the evolution of the displays over the project:

1.8 inch, 2.8 inch, 3.5 inch, 4.0 inch

I also added the Adafruit Powerboost 1000 and a rather flat 3000mAh LiPo to the mix. The Adafruit is rather expensive (20-30€) and only supports 1A charging current, I’d love to have a cheaper charger board with 2A at some point in time.

With the power source in place, it was time to wire it all up. Note that I added another switch to the keyboard so that I could switch off the keyboard but let the Pi run for background computations.

As you can see, I wired the USB hub directly to the Pi to save some more weight and space:

Wiring the OTG USB hub directly to the Pi.

Another trick to save height with also the new Hyperpixel display (the plug of the screen is okay, so I needed a new Pi Zero without the DIPs and just short pins), is to solder the pins with the plastic spacer from behind and then remove it plus the excess pin lengths on the back:

After the system was established, it was time to design the case and get a feeling for the locations of everything:

[earlier version with the 7 port USB hub and 3.5inch screen.]
[earlier version with the 3.5 inch screen and first attempt to make the display switchable.]

A later version then had spacing elements between the components to hold them in place. Also the HDMI output cable was added then:

As mentioned before, the screen switch for the 3.5 inch didn’t work as you could switch it off (cutting off 5V with the physical switch) but not on again since the OS wouldn’t re-recognise the screen then.

So the whole case design (TinkerCad) underwent a couple iterations:

As you can see in iterations 7 & 8, the battery was rotated 90° to landscape and the HDMI cable is going between battery and battery charger.

During these iterations the device grew a bit in dimensions to a final 11x14cm. That’s 3cm more than the original keyboard’s case at 8x14cm. But anyway that’s the price for a 4inch screen with a 800×480 resolution…

designing the holes for the keys is a pain in the butt…

So that’s the currently final layout:

Time to look at the functionality in a video:

FIRST BOOT UP!

As I wanted to take the PocketPi to my easter holidays, I needed trade the flat screw “lips” to be bold and rounded to give the hole thing more stability:

bold screw holders, not nice, but survived the holidays / travel.

I installed Raspbian Stretch lite and added the Pixel desktop plus Geany as python IDE. I also configured two of the buttons to zoom the text in Geany, the right mouse key on the keyboard is really handy, the touch screen works as left mouse button and I added multiple desktops to easily switch between apps. Here’s a video of the currently final device in operation:

LOVE the keyboard illumination.

As I have promised on the Facebook Raspberry Pi group, here are the STL files: https://www.thingiverse.com/thing:3623114

Here is the shopping list:

It’s roughly 130€ plus 3D print.

Woah! Featured in:
hackaday: https://hackaday.com/2019/05/16/pocketpi-is-exactly-what-it-sounds-like
hackster.io: https://blog.hackster.io/pocketpi-raspberry-pi-zero-w-keyboard-computer-is-an-iterative-success-981821d46c48
geeky-gadgets.com:
https://www.geeky-gadgets.com/pocketpi-raspberry-pi-pocket-computer-17-05-2019/

StickPi – a Raspberry Pi Zero W with GPIO buttons and an e-paper display

UPDATE: HACKAYDAY featured StickPi! So honored!

I always wanted to have a sturdy and rigid Raspberry Pi that is mobile and as small as possible. Recently I designed a Raspberry Pi 3 plus 5 inch display, built-in keyboard and a battery / charging circuit. It’s nice as it’s about a DIN A5 paper sheet.

Then I came along these USB boards that you can pogo-pin to your Pi Zero which is similar in design to what the guy at NODE did.

Pi Zero and USB power board

When working with a Pi Zero, I wanted to connect via VNC so I can run Pixel desktop and Geany on the Pi to develop and run software. When doing so, you quickly want the Pi to display the Wifi and IP address it’s connected to. I chose an e-paper display from Waveshare (do yourself a favor an buy the balck/white display only, not the one with three colors as they don’t support partial update, i.e. they refresh very slowly!) and bought such a USB power board and attached the Zero to a battery:

Pi Zero plus epaper plus USB board and battery

Once you have this kind of display, you learn that the physical interaction with the machine is one way: consumption. And immediately, you think that it would be nice to have interaction methods to select a WIFI or shut down the machine or select operation modes, etc.

So I sat down and designed a PCB (not printed but wires on a protoboard with a pretty ideal size), to add some buttons for directions as well as two “shoulder buttons”:

three pieces 1

To keep the design compact and as the e-paper display would consume the full GPIO, I soldered the pins on the Pi to go through the PCB:

three pieces 2

I chose a wiring that can actually use buttons without additional resistors and so the whole system works with only input ports as well as GND:

button gpio wiring

This led to a compact design alltogether, see also the first version of a PETG designed case:

The case itself is designed in Tinkercad and I made the case available on Thingiverse:

StickPi TinkerCAD

Pi in case

There is still room for improvement for the case but right now I’m happy enough with it to actually keep it and write software. Querying the keys is really easy:

 

button read  code

Finally see a little interaction of the buttons and the screen here, the software is really simple to query the buttons continually and display values on the e-paper:

(On the top left, you see the Raspberry Pi 3 case with the keyboard integrated, still not happy with that design, that’s why I haven’t published it yet.)

I may venture into actually designing (EAGLE files) and ordering PCBs for the button to make the whole thing more “defined” and better fitting the case.