Like many people into electronics I’ve always had the hankering to build my own portable system. You will often build a PC from components and very carefully select their pro’s and con’s to meet your specific requirements, This is frequently more difficult with portable system.
After finally giving up on getting a working Pandora, I’m ashamed to say while they were built in my own country the build quality was sadly rather poor. However I’m glad that I did have various semi working Pandora’s because they did make my mind up on a number of points
- It must be open source – ideally everything circuit diagrams, datasheets, software and ideally no driver blobs.
- While it might be nice to multi boot into Android (ASOP) on the odd occasion for me in terms of programming on the go, applications, freedom etc it has to be Gnu/Linux!
- The graphics and CPU for that matter should at least have enough grunt to allow moderately complex OpenGL applications to be created and run
- All the usual things you’d expect like Wifi, Chargeable battery etc. but with some exceptions
- The screen should be a decent size, so bigger than a phone, but still something you could just about get into a jacket pocket
- SATA – probably a bit much to ask for but an actual harddrive in device would be so much nicer than SD cards in terms or reliability and speed.
My design decisions were not just dictated by must haves but also by a list of things I was quite indifferent to (my Meh list!)
- GPS / compass – I don’t have a great use for this as if I need to find something in a strange town I’m as likely to use my phone or shockingly ask someone!
- Accelerometer / Gyro / G sensor – I often turn screen rotation off on a phone or tablet and do it manually, the device doesn’t know the orientation of your head and gravity doesn’t always point down!
- RFID tag / RFID reader – Something that might allow retailers to track my physical movements – no thanks, as for a reader I really can’t see a need for it myself…
- Camera – I have a good quality camera if a focal length that no portable device is going to match… again for a quick snap there’s the phone in my pocket and video sexting isn’t my bag 😉
- built in analogue stick, keyboard, fire buttons etc… Gaming isn’t my primary concern, that said there will be USB ports and I may well make a tablet lap-perch / sleeve thingie that I can plug the tablet in, that should have keyboard / joystick – add a wireless mouse and that should do the trick.
- 3/4 G I thought long and hard about this there is always tethering but the only real use I have for mobile data is an occasional price check most times for anything more substantial I’ll be inside a WIFI footprint.
- built in FPGA – well no… if I want to design some custom circuit I’ll wait till I’m back home! this isn’t going to be a monster bitcoin mining monster!
Well so much for thoughts on design then, how about practical considerations… My initial investigations into displays (for me what seemed the major hurdle) resulted in disappointment whenever I looked. All I seemed able to find were really VERY expensive displays at disappointing resolutions or worse still great looking kit that turned out to be vaporware (very frustrating) … months went by…
It seemed the way to go would be to salvage an LCD panel from a netbook and find some kind of HDMI -> LVDS / power board – again more vaporware and more disappointment. Finally it looked like I had an excuse to get into FPGA’s ! YaY – no where as difficult to get into as I expected and before long I actually had some kind of VGA controller working, as practice for the glue I’d have to build for whatever LCD panel – I knew it would be hard… but I was sure I could do it.
I spent a long time looking for some kind of SBC to base my design on and this was very much because of the design choices I had made. For example the Raspberry Pi was a possible candidate for a while but although its touted as an open source machine as many know it has a dirty little secret – the slave (arm) CPU eventually got open source drivers or rather interfaces but the master (gpu) processor that really runs the whole show is strictly an off limits propitiatory black box, single core, a little slow and not massive amounts of memory – especially if you favoured the GPU eventually all ruled this SBC out.
So with not a massive amount of hope I kept looking, one night while browsing near to bed time I stumbled into this website – hardware looked good, there even seemed to be some displays… tired I plodded off to bed.
Then I had a feverish dream…. The SBC had open source GPU drivers faster than the proprietary ones… it was dual core….. it even had just about enough RAM… there were lots of interface options… 100’s of GPIO pins (literally) …. there seemed loads of sensor modules too…. and the kicker it had a SATA interface… what a LiPo charging circuit? WOW! ….and then the dream just went wild, not only were there LCD modules, but included in the price were interface boards that you could just plug directly into the SBC and they would just work…
Of course all this would mean that the price MUST be through the roof, but wait the more I looked these prices seemed realistic – it would be economically practical and even desirable to build something with this….
Of course I was dreaming!!! Never the less the next morning I determined to clear the fevered fog from my mind and take a proper look at the olimex site I had discovered. I literally could not believe what I was looking at, I actually wasn’t dreaming, this was affordable good quality kit and these weren’t some fly by night vaporware company, these are guys supplying the likes of Digikey, Mouser and Farnel none of these guys are going to deal with anything other that the real deal!
Well after a day or so thinking about do I make a laptop, or a tablet (or both!), I flexed the old plastic friend and bought an A20 board (which the spec reads like they followed everyone’s wish list and added a few extra bits) and also a 7″ LCD touch screen, with a few other bits and pieces I decided I’d need not forgetting TAX and postage it came to a little over 200€ which amounts at the time of purchase to something in the order of £165 – that includes a LiPo battery too – sure I’ll need to make myself some kind of enclosure but these guys have just made my dream an economic plausibility!
So now all I have to do is….
- wait for it to arrive…
- assemble it…
- make the software stack work how I want…
- make a enclosure that will fit in a jacket pocket…
- not much then…
but think on this – basically its just an assembly job, probably no electronics involved! I wouldn’t want to be a laptop manufacturer in the coming years….
BTW I’m in no way involved with Olimex – just amazed at their products that answer so well a problem I’ve been chewing over for literally years.