Pocket Computer Project

by Elijah


This project is suspended at the moment, as I discovered that I might be able to get an Aspire One D270 netbook down to 7 W power consumption, thus being able to power it by solar panel.

Hint: boot Xubuntu live with a large-ish permanent-storage virtual disk from a fast USB Flash memory, auto spin-down internal HDD (hdparm -s command in /etc/rc.local) and use HDD sparingly if at all, reduce screen brightness as much as possible, have a triple-capacity battery.


My Motives

Ever since my life changed to a more spiritual path, I was more or less living as a vagabound, spending some months here and there, without a real home (sigh) – living with no more than I can carry on my back. This leaves little space, so that the necessity of carrying is constantly re-evaluated with every piece. During the past couple of years, I spent half of my time literally in a cave in the desert (no joke!). Those who may think now that such a hermit's life is necessarily a meager one, may hear and see differently: Although I spend a lot of time away from power outlets and other comforts of industrialized civilization, I still use some pieces of technology, for work and communication. Just because I'm enlightened does not mean that I suddenly don't remember how to use a computer (paraphrasing, I think, Terence McKenna, please correct me if you know the quotation). So, I was sitting there in my little cave, with my now-obsolete Nokia smartphones (good old E7 and C7 from 2010 with "Delight Belle" Symbian OS), a bluetooth keyboard and a solar charger, writing lenghty texts, recording and transcribing shamanic channeling sessions, e-mailing, and doing the occasional webserver maintenance per SSH. All is possible, although with the handy little C7 which is just a little less reduced in functionality than Android devices, such tasks can be a copious endeavour.

 ▹ here comes a rant, click to see more

Now, I feel I want to have a more capable pocket computer, but neither I want to have those Microsoft's nor the Google's or the Apple's toys. To have my netbook solar powered, the combined weight would approach 2kg, and it would account for quite some bulkiness. A tablet running open software on open, affordable, fair-trade hardware would best suit my cause, yet no such things are currently available. Therefore, I will have some tech fun in building my own. Sure, it's not going to be a super-flat, do-it-all, foolproof pocket gadget. But those wires-in-a-box will only add to its awesomeness!

Requirements

What Features I Think It Requires

Good-To-Have

Non-Requirements

Hardware Selection

For some years now, kickstarted by the famous Raspberry Pi, there developed a whole ecosystem of cheaply produced, more-or-less open source, compact single board computers (SBCs) that are good for computing projects which require more than a microcontroller could do. They all employ SOCs (system-on-a-chip) that integrate a processor with a lot of peripherals and ports found in modern PCs into a single IC package, while being extremely energy efficient. Many of the SOCs used in SBCs are otherwise put to work in embedded systems and portables. Many currently manufactured SBCs are well capable of running current Linux, including full desktop environments.

For my purpose, it became clear very quickly that using a Raspberry Pi (3) would put me to many limits (low on RAM and clock rate, missing RTC, USB-connected SATA, lack of power management, etc), although it would probably have the best community support available. Therefore, I spent some days researching viable alternatives. Following is a list of what came up. By the details given, one can already see which devices got my most interest. I list only those features which are of interest for this project. This list is by no means complete, I can not guarantee that there are no devices which would be more suitable.

Now, there is a plethora of (cheap) boards available for the task. Some of them, it seems, have been made to quickly cash in on the SBC hype. Products are shipped in beta stage, often lacking driver support for all functions, designers violating the license by keeping sources under their cape, while relying on the "community" to help get the software running (and being uncooperative in that).

"Banana Pi" products

 ▹ Click to see more

NanoPi S2 (FriendlyARM)

product website see the comments here.

Dropped from consideration due to lack of kernel support.

Odroid C0 (Hardkernel)

 ▹ Click to see more

CubieBoard3 / CubieTruck (CubieTech)

A warehouse full of features, full open-sourced, with plenty of community support – but also at about €100 outside of my intended price range. Until I found out that I could probably get a CB3 from a second-hand source for half that money, SSD included. So this is currently my favourite.

product website
schematic
A20 SOC datasheet
board closeup pictures: front, back
Power Management IC (PMIC): AXP209 datasheet

drawbacks:

Issues with the CB3