Category Archives: arduino

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  • And a yet unpublished 5in screen slate design.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.

Trashbot upper body and neck servos revived

I recently split my Trashbot in half to finally get hold on the walking patterns of the lower part, as I changed the controller from Arduino Nano to Raspberry Pi. Here’s the upper part:

Trashbot upper body incl neck & head

Trashbot upper body incl neck & head

With the recent progress of running Oculus Rift from a Pi 3 and the experiments of streaming video from the stereo cam Blackbird 2, I thought it was a great idea to attach the camera to the upper part of Trashbot and send the Oculus head orientation to the neck controlling Arduino Mini Pro.

First step is to get the Arduino run with the PC again. But oh, that shitty servo:

So, before diving deeper into head synchronous robotic telepresence, I’ll need to fix that bugger…

Arduino Tamagotchi, first power up!

That was more intense and exciting than I anticipated! I thought building my first “homebrew Arduino”  from an atmega 328p and controlling an OLED via I2C shouldn’t be too complicated.

In fact, it isn’t, but there are a couple of things you have to think of, especially when you do it in this contrained space.

20161204_173740sAnd actually, you can see the wiring mistake I did up there, I connected the RST of the chip and the DTR of the FTDI port wrong. But chip, FTDI and capacitor survived it…

I also did the buttons wrong as the buttons were rotated and always ON / HIGH. So, I changed the layout from this:20161204_183737s

To this:20161211_212541So now the power is on the upper part of the buttons, instead of the right (for the left buttons).

Yeah, so finally, here’s the first power up! The date / time is wrong because the third perf board with the RTC and the speaker are not connected yet, so the clock starts when the atmega is powering up:

 

 

Arduino Tamagotchi – first board fitting (Pt 2a of 3)

The design principle of keeping everything to a minimum is also paramount in the Tamagotchi project. In this case, I wanted to use the Arduino chip itself and layout a board around it by myself and luckily, I also found out that my slaughtered external phone battery delivered 5.1 Volts which is in the operating range of the Arudino.

Tamagotchi PCBs

Tamagotchi PCBs

Top left, you see the front board with the display and the intended buttons (only one placed), top middle the board for the Arduino and it socket plus an USB port that will be used for the LiPo charger board (the one that is close to the battery) and on the right it’s the back plate containing the speaker and the RTC board. Continue reading

palmsize Tamagotchi

Recently, I’ve come across a really nice Tamagotchi project on Instructables.

Tamagotchies are virtual pets in little devices (later on also apps, etc) that the user has to feed, clean up after and play with. They are a nice addition in my thinking on social robotics. Also while still collecting knowledge for the 68k computer, I learned that I want to start with a stripped down Arduino, not a Nano I usually work with. So this is an ideal little weekend project to learn a few things. Continue reading

first “unit test” in programming an arduino mini pro

so, after i’ve connected the head and its servos to trashbot 6, it’s now time to work on the actual control of the neck servos. unfortunately, the servo-board connected to the raspberry is not sufficient to control the neck servos since the body is already using 15 servos and the controller only has space for 16.

so i thought to use an arduino mini pro for this since it has 6 PWM outputs that can control six servos (people have noted that the output pin doesn’t necessarily have to be capable of PWM to control a servo). Continue reading

trashbot 6, quick video walk through

most of this work has been done over christmas, but only now i found the time to at least do a quick tour around the bot. here are some highlights:

  • arduino nano changed to raspberry pi 2 & wifi
  • moved controller from back to hips
  • added 16 channel i2c servo controller
  • new foot construction adding an additional degree of freedom (DoF)
  • reconstructed legs that are lighter and now take up new batteries
  • power distribution board including i2c current / voltage measurement
  • accelerometer and gyro sensor (i2c) moved to “belly” instead of neck
  • added arms with shoulders (two DoF)
  • changed spine, reduced complexity
  • removed head for now (being redesigned)

Trashbot 5, new hips, first movements

Last week I added three degrees more to Trashbot, two hip servos for forward movement (“kicking”) and one to the bone.

This week I found some time to do the first single servo movements and tests to check out the new geometry of the bot since the broader hips will affect the Center of Gravity etc. Here’s the first attempt to do what the normal gait would do: shift the body to one foot:

So, definetly software teaching me how to improve hardware… Next draft iteration: Continue reading

Working on more Degrees of Freedom in the legs of Trashbot

I’ve been working on Trashbot for quite a while now, but the basic gait mechanism is still the same as in version one. The hips’ movements and the distance between the legs define the possible step length. This is annoying since the robot is rather tall and you’d expect that he’ll walk a bit faster than he actually does. However, moving faster induces stronger vibrations in the skeleton and makes him fall much easier.

trashbot 4 in full length

Also, the upper part of the body will tilt “stronger” when Continue reading