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The Plan...

A project log for SPACE CAADET

Simple, Portable, Ad-Hoc Computational Engine for Communication, Amusement, and Additional Distinctly Everyday Tasks

starhawkStarhawk 07/17/2020 at 21:100 Comments

I'm going to throw together something with (mostly) what I have. A lot of this pulls from the leftover debris that is the remains of the "SETEC Astronomy" project, and incorporates a few of the lesser goals of that project.

I have an HP multimedia keyboard, a "standard" (102/104/etc-key full-size) PS/2 model, that my tech shop friend gave me. That's going to be a major part of this... it will serve as the main chassis, essentially, with the rest of the stuff mounted to it (or *in* it, in one particular case) -- an LCD, a USB 2.0 hub, a USB3.0 extension cable, a touchpad mouse, and the system unit in a rather *ahem* unusual and decorative casing ;) I'll also have a battery unit going here :D I've figured out an easy way to do that...

The screen is one I impulse-bought on eBay for "SETEC" and didn't get a chance to show off -- I got it, entirely unopened and unused (heck, the shrinkwrap was still on it!) for a THIRD of what I'd have paid a CN/HK seller to send it via SpeedPAK or ePacket, simply because the guy who bought it never used it! It's a 10.1-inch "Ultra Thin" 1024x600 LCD monitor -- it's not just a panel and a board, it's got a housing and everything. It has capacitive-touch buttons for power and the OSD menu, right on the front of the thing, and it's got audio handling (unlike the 7-inch Waveshare and Waveshare-clone displays I've been using) and a speaker in the back. On top of the rest, it runs on 5vDC just fine, despite being rated (and labeled) for 12vDC operation. This mucks up the colors in anything other than HDMI mode, but I don't care -- I'm going to be using HDMI. I've removed the original barrel jack and will be hardwiring it.

Unfortunately, the monitor's controller-board design shows the usual, er, "Chinese innovation" as far as BOM count and shameless simplification is concerned, ugh. The way the audio chip is wired, it only outputs audio on the righthand channel (!) -- the lefthand channel is not wired to a speaker -- and although the chip has the *ability* to auto-detect when headphones are inserted, this feature is not used and that pin is tied low (disabling that mode) with a pin that goes under the chip! The little stub of trace that sticks out from the chip pad is so small I can't cut it... and the line has to be pulled high to enable headphones mode :( Of course it's also a surface-mount chip, an SSOP-20. I'm going to pull the speaker off, it's on a connector so that's easy, and just use a USB headphone adapter I have already. The speaker looks like something from one of those awful birthday cards that sings to you, and even the really good ones of those always sound incredibly awful -- and this speaker didn't come from one of the good ones! ;) so it's guaranteed to sound criminally horrendous. Screw it, I've got a Plantronics audio dongle that will do much, much better!

The USB2.0 hub will be integrated into the keyboard housing. It has four ports... one I'll need for the USB audio dongle, one for a PS/2-to-USB adapter for keyboard and mouse (more on that later), and one for a nifty little adapter I got from Adafruit (eBay would have been cheaper but it would not have gotten here in time unless I paid $20+ for EMS service -- which of course would make it *more* expensive than Adafruit) that works part of the battery subsystem (again, more on that later...). A single port is left for other uses... we'll see if I need it. Probably it will get a WiFi card if the onboard decides not to behave, which is all-too-often indeed the case (for shame!).

The USB3.0 cable simply breaks that port out (the system unit has one USB2.0 port and one USB3.0 port) to a convenient location so that I can stick a flash drive in it.

The touchpad mouse is an ooooold model. It's the one thing (so far) I purchased purposefully for this build other than a little bit of hardware (hinges and such). It's a "Cirque" brand model, a "Smart Cat Pro" touchpad -- the one with the scroll buttons. Per the label, its guts are apparently a Glidepoint construction, not that it matters, and it's old enough that the native protocol is... RS-232 LOL. Yup, it's a COMport mouse that's switchable to PS/2 with a handily-included little adapter (which I will of course be using!). Nifty little bugger. It's also quite large. I'll be bolting that on so that it hinges flat over the keyboard's numpad when the system is off. The cable on the touchpad will need a little gentle re-routing for that, since it comes out the back and will therefore be in the way, but I don't think that's going to be too much of an issue ;) I'll redirect it out the left side of the unit (it comes out on the left-rear corner at the back, so that's the easiest way to fix it), so that it goes over the keyboard, and I'll make it decorative somehow with that.

The system unit is the one from "SETEC", an Intel Compute Stick brand Compute Stick (LOL) with an Atom x5-8330 SoC, 2gb DDR3L RAM, and 32gb eMMC storage. It's going inside, of all things, an orange pill bottle that will have some LEDs inside to make it look extra-pretty. I'm using the integrated fan, for once, and probably won't bother with a second one... I really don't see the need. Unlike the MeeGoPad units, this stick PC is quite well designed as far as thermal dissipation is concerned. The pill bottle, BTW, will have vents and port-cutouts put into it, and will be mounted to the keyboard on a hose clamp.

The battery subsystem is actually a [Hackaday]-enabled setup. Thanks to an excellent article published in regards to some work done by another fellow who was frustrated with an eBay purchase ("item not as described" -- the design of the apparent RasPi UPS HAT, sold under a "Geekworm" throwaway 'brand name' (who comes up with those names, LOL?!), was so heavily "simplified", in the usual manner, that it really didn't actually do the job it claimed to) and, rather than pitch it or drop it in the part-salvage bin, he decided to fix it with a minimum of componentry and expense. [Maya Posch] did the write-up for [Hackaday], it's at https://hackaday.com/2019/08/27/fixing-a-cheap-ups-hat-for-your-raspberry-pi-with-a-tiny-daemon/, and both the article and the work behind it are quite excellent. The even better part is -- *any* power bank can be used with the additional module that [Joachim Baumann] created. It's an ATTiny85 and a few passives, and it's an absolutely brilliant design. I have a six-18650-cell-maximum power bank, one of the ones that comes as a "kit" (PCB and housing; BYOB batteries), and a set of four 2000mAh cells that Wal-Mart sells in the garden center for solar lights... they're supposedly Westinghouse brand, but that's an absolutely shamelessly-obvious blatant license deal, so I'm a bit leery... we'll see ;) but in they go, with the module and that USB adapter I mentioned tagging along beside.

That adapter is basically a USB-C (ugh! MicroUSB would've been fine... or, better yet, USB Mini-B, get off my lawn!) breakout board for an FTDI FT232H chip. Note the '-H' there! It's not *just* a USB-to-RS232C adapter ;) This chip also provides SPI, I2C, or SMBus functions, and up to eighteen GPIOs -- mind you, two of those eighteen GPIOs are needed for I2C or SMBus functions, and four for SPI... or six of them for RS232C. Unfortunately, all of these pins overlap -- you *have* to choose between RS232, SPI, I2C, or SMBus (which is essentially an alternate I2C mode). Separately, there's also a "Stemma QT" connector for Adafruit's knockoff of the Sparkfun "Qwiic" interconnection 'standard' (which was already unnecessary cruft, LOL... but, hey, do what you want, guys).

Laptops use SMBus to communicate with their batteries, and [Mr Baumann]'s work uses that -- hence the need for the adapter. The only issue is that I've got to either find an adapter for the adapter (LOL) or get a USB2.0 Male-'A'-to-Male-'A' cable, because the only USB-C cable I have came with my phone and I need it for that (it's the charge cable). Of course, I could just buy more USB-C cables, but this is Hackaday and we don't do that sort of thing here! (Besides, I'm out of money till next month, and the "Making Tech At Home" contest, which I want to enter this in, will be over by then.)

OK, yeah, there you go, that's the design RN.

IMMEDIATE EDIT: realized I'd pressed "Publish" without writing the last line. Fixed, lol.

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