Printing a handheld PC

Have you seen this? https://hackaday.io/project/9082/gallery#68358f511c84a57ec18391e1d8f8b162

The design is ugly, but the guy actually used a Jornada 720 keyboard! It would be nice if your device could fit on the Jornada case and even use the Jornada keyboard. It would probably be hard to reuse the screen though. And finding another screen of the same size is quite complicated

Not exactly easy on the eyes...Yeah, with a face only a mother could love! A 3D printer could sure help with the appearance in this case. But a great idea...is the J720 keyboard pinout standardized?? I recently was daydreaming about taking one of my discarded Samsung 5 cell phones and duct taping it like a hinge to a wireless keyboard or maybe to the bottom half of a J720. Then I might compete with this in the looks department.

Wow, the looks do leave a little to be desired... I like the little thumb pointing stick though, and his use of the Jornada keyboard as you noted.

I had a look at doing this inside a (broken) Jornada 690 case but it was beyond my capabilities. The components are quite tightly packed and even with most of the internals removed there are few truly useful spaces inside. One possibility might be to design a case (for 3D printing) externally similar to the Jornada case but with a nice big void inside.

I have found a few 6.5" screens with the same aspect ratio as the Jornada, only issue then would be fitting in the controller board to get the Pi (or other SBC) to speak to it. Thankfully modern LED-backlit TFT panels are a good bit thinner than the panel in the Jornada so it might just be possible to fit it behind the panel inside the lid.

My 'HPC' is much closer to an NEC MobilePro 900 in dimensions, as this was my favourite HPC. However once I'm happy with that I would love to take on something more Jornada-sized. A good bit more difficult though!

The pinout isn't what I'd call standardised but as with most laptop keyboards I've encountered the ribbon cable just carries the keyboard matrix so with a multimeter to work out the matrix layout and something Arduino-based like the Adafruit Teensy https://www.adafruit.com/product/2419 you could turn it into a USB keyboard. Then it's just a case of connecting it to your phone via an OTG cable. There are even Arduino-compatible boards with Bluetooth https://www.dfrobot.com/product-1259.html so you could even make it wireless if you so desired...

Again an idea I've spent quite some time thinking about, but the last few times I replaced my phone I sold its predecessor so there are no remotely recent 'spare' ones here. I'm pretty sure a HTC Desire is slower than the slowest Raspberry Pi!

Minor update on my project:

I've finally found a power supply board for the Raspberry Pi that I'm happy with. It claims to be able to supply 3A (at 5v) and I have tested it with a Pi 3B+ with all my peripherals connected, as well as a little USB light I had just to increase the current draw further. No issues running from battery, or connected to a charger, or whilst connecting and disconnecting. This is by no means a given with these types of boards in my experience, but on the basis of this I am prepared to believe the specs are at least close to accurate. I am confident it will supply a Raspberry Pi 4 with sufficient power so I can press ahead with my Pi-based design for the second prototype. As soon as I get hold of a Pi 4 I'll make sure it works, but I'm waiting for the next revision as they seem to have released it with a few issues.

I'm fairly well on with the design work, I expect to have a finished CAD model within the month and then I would expect a further month to build it, allowing of course for corrections and modifications to the design as I go.

In the meantime please see below a photo of the inside of the current prototype. I will definitely be simplifying and tidying the cabling for the new prototype!






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Pi-HPC Internals.jpg (95KB - 1 downloads)

wow, cool. How long does the battery last on a charge? What does the monitor and keyboard look like?

With the current battery setup (4 x 3000MAh 18650 cells) and a Raspberry Pi 3 B+ I get something around 4 hours' continuous usage (active, with the screen on) and around 12 hours in 'standby' (not a true sleep mode - implemented by turning off everything that can be turned off on the Pi). I have not yet incorporated brightness control for the screen so expect to improve the 'active' power consumption significantly when I do this (simple procedure) - as it is the screen is at maximum brightness whenever it is on and as you can imagine this is not necessary most of the time. 'Standby' power consumption is a little harder to improve as I have done most of the easy things.

The machine is currently disassembled as I am deep into the design of the next version and constantly measuring components. However I have an old photo from when I first put it together that should give you some idea. For reference the screen measures 7 inches (diagonal) and the keyboard is 205mm (~8.1 inches) wide.







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Pi-HPC Prototype 1.jpg (99KB - 2 downloads)

It's looking really good!

Looking good!

That website looks familiar

Yep, the website looks familiar... I wonder why?

The handheld is looking superb!

I thought it would be only fitting if the first website it visited was this one, I will be doing the same when my second prototype is built!

Speaking of which, I have a couple of screenshots of the CAD model showing the whole machine. I would estimate the CAD design is about 90% complete, there are some internal fixings yet to be finished and I need to finalise my cable routes and make sure there is room for them all. Time to order the remaining parts I think.

I've kept the same footprint as previously but taken as much off the thickness as I could, whilst still fitting in a full sized (unmodified) Raspberry Pi 4. Hopefully the measures I've taken to do this haven't hurt its appearance too much. I didn't manage to lose a whole 10mm off the thickness sadly, but at 30.5mm (1.2 in.) it is quite noticeably slimmer, even from just a model.

Today I've been working on the hardware side of things down in the shed / workshop - I managed to track down and largely eliminate a noise issue I had with the amp / speakers (simple grounding problem), and followed this up by getting the brightness control working on the LCD. This is driven by the Raspberry Pi's GPIO pins so I can do neat things like progressively dimming the screen following inactivity or when the battery is low. This is far better than my usual success rate!



Edited by robertojones 2019-08-11 12:42 AM








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Pi-HPC Prototype 2 Front.jpg (64KB - 1 downloads)
Pi-HPC Prototype 2 Rear.jpg (65KB - 0 downloads)

Mini-update on my project:

CAD model is basically complete. I'm playing around a little with colour combinations (see below for my favourite so far) but really just need to get on with printing the parts. I've got a few more electronic / wiring bits to sort out but these can be sorted while I get the printing under way.

Since my last post I've managed to wreck my Raspberry Pi 3 B+ (by slipping and bridging 5v and 3.3v pins with a multimeter probe - very silly and instantly fatal to the Pi). Naturally I took the opportunity to replace it with a Raspberry Pi 4, and I'm pleased to report that my chosen charging board runs it quite happily under all the use cases I've tested. Once I've got my 'sleep mode' code working again (completely new SoC on the Pi 4 means some commands have changed) I'll do some battery life estimates.

Edited by robertojones 2019-09-09 12:05 AM






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Pi-HPC Colour Scheme 1.jpg (44KB - 0 downloads)

Wow I don't think I've seen a micro trackball in something since the Dell Latitude 433C back in the mid-90s!


I'd lose the bump for the logo, modern design is clean, clean, clean.

Looking good though!

Roberto,

Your designs are and prototypes looks great!

Would love to have one of these....



Thanks for sharing.

Mark

Trackball is a bit of an odd (or old-fashioned) choice, I'm happy to admit, but I didn't really want to make room for a trackpad (I think it would make it too laptop-like as well as larger than I want). ThinkPad-style stick pointers are another option but I didn't find anything standalone of that sort. Could probably make it optional though, I need to try one of those battery-powered 'active' styluses (stylii?) on the touchscreen and see if that's a better option.

I'm not a fan of the bump either, it's there to clear the HDMI connector on the back of the display so I thought I'd stick a logo there to make it seem more like a design 'choice'. Does seem a bit inconsistent with the rest of the case design - may have to think about relocating the socket instead.

Thanks for the input!