Tuesday 16 December 2014

Motorola Photon Q (XT897) SIM mod

Original version is here: http://forum.xda-developers.com/showthread.php?t=1929143
Here's how my first attempt looks. Second one (next week?) should look neater I hope! It worked first time :)

The blue sleeve looked neat but was far too wide to stay. Although the pads are tiny, the pin pitch is huge so shouldn't cause any issues soldering unless you don't see the resistors just inside where the can used to sit

The tape is there for extra electrical insulation and to hold the springy wire in place... The SIM slot is soldered.

I removed plastic up until the antenna, and it fits with no room to spare

Sunday 7 December 2014

GB EPROM cart finally built, after about 10 years of never getting around to it!

Everyone's done one of these so I won't add much other than some photos. I already had the stuff... except the PLCC socket - I was still using UV EPROMS (DIP!) when I first got the rest of the stuff.

See kids, this is how you *actually* do a real ROM dump... none of that nandroid(etc) cheating! No virus-filled rapidshare downloads and a poorly written msword doc for this either!

Yeah, this was totally not worth the effort that went in to making it :P

Saturday 22 November 2014

MTK (Mediatek) debug cable

Reverse engineering crappy Android Linux hardware/platforms is much easier with a serial console when you have a working kernel, but no source (of course first attempt being GPL request, then when that fails, github/google). Many (most?) cheap smartphones at the moment are made using Mediatek SoCs like the MT6582, MT6589, or older MT6572. An interesting feature I found in these is that after the preloader stage, the LK bootloader and also the main kernel provides a 921600 baud TTL UART console port on the USB data lines, providing that it "sees" it during startup (else you get normal USB).

A "Prolific" PL2303HX cable will cost you about £2 from ebay. A CP210x might be a better choice, but they were just open boards so didn't look as nice.

The "2 minute" version is just swap the cable for a micro USB cable. The phone will charge if you connect the 5v wire, but the safe approach would be just connect the other 3 and leave 5v disconnected. Note that I put the green and white TX/RX the wrong way around here, on purpose to demonstrate what not to do *ahem*

That's the easy way... but the 5v input meant the phone boots up as soon as the cable is plugged in, which wasn't ideal. The few hours battery was no use really. I could have just put a switch on the cable - but that would have looked a mess. I opted for switching this using the DTR signal (ctrl-T in picocom). You might get lucky and find that DTR (pin 2 on the PL2303) is already connected up to a spare track or pad, but if not, SSOP isn't too small:

Take some switching parts from an old PC motherboard or something, I used a P-Channel MOSFET, NPN and a 10k & a 1k resistor, as shown in this non-standard & badly labelled diagram:

I tested it before compacting it! (also added an LED to show charging on/off). The phone is on the other end of the cable here... the LED isn't drawing 700mA :)

There's plenty of space to fit it inside the USB plug. If you can't use SMD parts, it'd probably sit above the PCB without issue.

The finished cable. "Why that horrible green?" - stops me thinking it's just a normal micro usb cable and plugging it in to something else and exploding it

Tuesday 30 September 2014

Internal usb flash drive conversion (aka DIY USB DoM)

For a low-cost alternative to a commercially available USB Disk on Module, I made my own out of a regular USB drive and a 0.1" 5x2 pin header (ebay, like 20p each)

Retail: £50 (GBP) + postage  (e.g. [link])
DIY: £4 (GBP)

USB drive that I used: Transcend JetFlash 350 [link]

I did manage to get hold of a "vintage" Windows Vista ReadyBoost(tm) Module (same thing, with a silly name)... but even that was significantly more expensive!

There isn't anything complicated here, but some tips if you're doing this:
  • Get the pinouts the right way around (it's mirrored)
  • Insulate the reverse of the PCB (the header has *two* ports). Kapton tape works well.
  • Solder the the NC pin to something - just to strengthen the connector
  • Melt a bit of plastic into the NC hole on the connector
  • If you use this exact same drive - there's 1 tiny plastic tab you'll need to snap off, and the "connector hole" needs (carefully!) making about 0.5mm wider for it to all fit back together. I opted for widening the casing, and filing the connector top+bottom; for a neater finish.
Here's some pictures:

These are annoying to dismantle without damaging the plastics

The "Vista" module I bought

If you're careful, you can save the USB connector for a future project. I was not:

 Hey, it works too!

 "In use"

The finished mod, and a side-by-side comparison with the one I bought:

P.S. yes, the cap still fits :)

Saturday 13 September 2014

"Zoostorm Desktop PC" - cheapo ebuyer i5-4460

I bought this a few days ago because it was cheap (£326). I couldn't find much about it beforehand, so planned to write stuff here... except they've stopped selling it :( That's probably why it was such a good price. Oh well, this will probably still apply to its replacement.

Here's what's inside it:

The motherboard is a Gigabyte H81M-DS2V
Western Digital "Blue" HDD
Corsair RAM
Akasa HSF
Generic Chinese no-name case and PSU

I was pleased to see it built using mostly branded stuff, and it runs almost silent when idle; and doesn't sound too bad under full load.

So, what's wrong with it? Just these (minor gripes):

The power light will burn your retinas off. Typical of cheap stuff, it's far too bright, and blue. Why are they always blue?! It was "cool" when the Playstation 2 first got released...

And this is what the horrible Gigabyte monstrosity of a bios looks like. Also it was Revision F2 out of the box... and they're up to F5 as of a couple of months ago.

Or you can switch it to "Classic"
(which is just as bad)

And if you want to use this for a diskless PXE client or something, pick something else. It comes with this "feature":

Finally, the SATA HDD came plugged into a 3Gbps socket rather than the 6Gbps one sat right next to it. Would it make a difference? Probably not, but still!

Sunday 8 June 2014

Linux Stuff

I've been messing around with various Linux-y things recently... anything that might be remotely useful to anyone else will appear here:

GitHub (stevenhoneyman)

...or maybe here: Arch Linux AUR packages (stevenhoneyman)

...Also, over a year since I last updated this blog/site...oops!