Sunday, May 1, 2016

Notes on the Gobi2000 in a Thinkpad X100e

The Qualcomm Gobi2000 is an internal Mini PCI Express 3G modem. It was used in a variety of machines including the Lenovo Thinkpad X100e.
It's a bit unintuitive to set up (to say the least) so I decided to write this post. Maybe it'll help someone else out there.

So right off the bat unless you're a Verizon customer do NOT just install the driver from Lenovo's site because it will default to loading Verizon's firmware. See:

If you already did you can uninstall and follow the instructions above or you can open the file: C:\ProgramData\QUALCOMM\QDLService2k\Options2k.txt and edit it.

The text file contains the path to 3 binary blobs which get loaded into the card's ram when the driver loads. Apps.mbn, AMMS.mbn and UQCN.mbn 
You just need to change which directory the images are loaded from. \1 is the Verizon firmware. For a full list see the support link above.
Note that to load the generic UMTS firmware you need to load Apps.mbn and AMMS.mbn from \UMTS and UQCN.mbn from \6 because consistency was not the developers' strong suit.

Also unless you're on a CDMA network that doesn't use a SIM card and requires an activation procedure instead do NOT install "Mobile Broadband Activation" either.

DO Install "Hotkey Features Integration" As far as I could tell it's the only way to enable the WWAN antenna. Fn+F5 brings up the radio power controls. It's also a separate executable so you can create a shortcut for it if you like. The naming is pretty straightforward, look through the installation folder in Program Files.

A note on all the abbreviations you can come across while setting up a 3G connection:
UMTS is the name of the whole 3G network technology, WCDMA is the name of the radio access layer used by UMTS networks. From a setup perspective they're pretty much interchangeable. HSDPA or HSUPA are high speed data services offered on a UMTS network. HSDPA offers faster download and HSUPA offers faster upload speeds. Together they are often referred to as HSPA. HSPA+ and Advanced HSPA+ are further iterations of this technology that offer even faster speeds.
And of course GPRS and EDGE are considerably slower data services running on a 2G GSM network.

Unlike Huawei or ZTE modems the Gobi2000 doesn't have a straightforward way to set which network and data service it should prefer. The automatic selection will be fine in most cases but sometimes you just want to force the setting. Like let's say the 3G network's signal is really weak and flaky but it's still faster than the 2G network that has good signal.
Apparently there is a method with the slow and clumsy Lenovo Access Connections tool but from what I can tell the setting doesn't persist.

I'm fairly certain the Lenovo tool just issues a manual network selection AT command. You can do that yourself (you can even add it as a pre-connection command to the Windows mobile broadband connection. It's there on one of the properties pages)
You can tell the modem to connect to a network by name but it's a better idea to use the network ID because carriers will sometimes name their 2g and 3g networks differently.

AT+COPS=1,2,"#####",0 (where ##### is the network id) will connect to the 2G network of the carrier

AT+COPS=1,2,"#####",2 will connect to the 3G network

To get the network ID you can issue AT+COPS=? to do a network scan (it will take a while) the 5 digit numbers in the list will be the network IDs

You can query the current operating mode with AT$QCSYSMODE?

On the 2G network I got simply GSM as the reply
On the 3G network WCDMA + HSDPA + HSUPA (which Windows listed as HSPA in the network list)
On another 3G network simply WCDMA (which Windows listed as UMTS)

You can also query the current network with AT+COPS?
You'll get something like +COPS: 1,0,"Network-Name",2

Note that the modem will return ERROR for most commands if it doesn't see a SIM card or if the radio is powered off.

Monday, April 18, 2016

[Random Teardowns] A couple of laptop batteries (aftermarket vs original)

Device: Original Lenovo 42T5225 (ThinkPad R61) and Chinese clone of 42T4788 (ThinkPad X100e)
Origin: Various
Reason for teardown: Broken
Impressions: I've recently opened up a few laptop batteries and decided to take some pictures. Keep reading if you've ever wondered just how different the Chinese aftermarket batteries are compared to the originals.

The original battery controller PCB is conformally coated while the clone is bare. Fair enough.

The original is based on the Mitsubishi/Renesas M37512 microcontroller (datasheet)

The clone on the other hand is based on the SINO WEALTH SH79F32 (datasheet)

Nothing terrible so far, right?

Well, if you take another look at the image with the original microcontroller there are two things worth mentioning on there. That component with the two long leads to the right of the micro is an externally triggerable fuse. It can blow during an overcurrent condition as any regular fuse OR the micro can trigger it in case of another hazard condition like say the cells overheating. Which brings us to the small flex cable temperature sensor stuck to the cell on the left side

Now let's see what the clone has in terms of overcurrent or overtemp protection.


Zero for two.

So the most the micro could do is (attempt) to shut the FETs off in case of an issue. (If it even noticed it before the cells set themselves ablaze.)

Lastly, let's take a look at the cells themselves.

The original has Japanese made Panasonic cells
The clone has Chinese made ChangJiang (CJ) cells
No surprises here. And it should be pointed out that these aren't necessarily bad or more hazardous than any of the high-end cells. If anything they're just unlikely to handle as many cycles before capacity loss renders them unusable. That said, a fuse and temperature monitoring still wouldn't hurt.

Thursday, October 29, 2015

[Random Teardowns] XL4005 5A step-down module with display

Device: XL4005 constant-current/constant-voltage buck converter with LED display
Origin: eBay / China
Reason for teardown: Project
Impressions: Ok so there isn't much to tear down on this given that it's just two PCBs screwed together with standoffs but oh well.

I got two of these for a project because they're just so cheap now. Supposedly they do 5amps and you get current limiting as well.

Already a bit modified

The modules themselves work reasonably well based on my limited testing. The display/monitor boards are pretty terrible though.

My gripes with them:
  • Horrible accuracy as-is and no calibration pot.  (FWIW you can hook up 10k trim pots to the two unpopulated resistor pads near the LM358 to fix this.)
  • Horrible resolution and pointless, wasted digits on the 7segment displays. (I'd take an extra digit over the lower-case u moonlighting as V ...)
  • Painfully slow update-rate
  • Serial feature poorly documented but also borderline worthless (see below)
All of these issues could be fixed in firmware. I'm almost tempted to get an ST-LINK dongle and reverse engineer the thing but it'd probably take about as much time as reimplementing the whole board using a microcontroller I'm actually familiar with and not bothering with the STM 8S003F3P6 it has which is to say: too long either way to be worth it. Anyone up for the challenge?

As for the worthless serial interface: the biggest issue is that the serial processing code takes too long to run and the micro isn't updating the screen while it's running so you get a really noticeable dip in brightness every time you send a query for voltage or current. And of course they're separate commands which compounds the problem.
If you're continuously polling the board with something you basically won't be able to see anything on the display.

If after all that you still want to use it, here's the info they give you:

Baud Rate : 9600 Bps
BB CC ADDR 00 XX XX CRC ( current return command )
BB CC ADDR 01 XX XX CRC ( voltage returns to the command )
BB CC for the header ( 2 bytes )
ADDR for the module address ( 1 byte )
00 to read the current command ( 1 byte )
01 is a read voltage command ( 1 byte )
XX XX arbitrary value ( 2 bytes )
CRC CRC checksum ( 1 byte )

Not bad. CRC is undocumented though and ADDR varies with board revision. (0 and 1 definitely exists)
Serial is standard 9600bps with no parity, 8 data and 1 stop-bits with no flow-control.
The revision with ADDR 0 may ignore CRC as long as it's not 0 because these have been reported to work with it:

Get current: BBCC00000000B4
Get voltage: BBCC00010000DF

It also doesn't return a CRC in it's replies and returns voltage and current in millivolts and milliamps (so a higher resolution than it displays) which is nice.

ADDR 1 on the other hand checks CRC and also returns it in replies. A brute-force loop later I got two replies with CRC and it was pretty obvious that it's just a simple addition you take the least significant byte of.

So the proper commands for ADDR 1 boards are:
Get current: BBCC0100000088 (  BB+CC+01+00+00+00 = 0188 so 0x88 )
Get voltage: BBCC0101000089 (  BB+CC+01+01+00+00 = 0189 so 0x89 )

Unfortunately this revision of the board returns values in 100 millivolts and 100 milliamps so for 4 volts you only get the value 40 .. FAIL!
And in case you're wondering if there's maybe an undocumented command you could use to get a higher resolution value or maybe a raw ADC value.. there isn't.

So in conclusion:
ADDR1 boards give you a low resolution value in exchange for a flickering or completely unreadable display.
ADDR0 boards give you a higher resolution value and I'm not sure if the flickering is present or not. Anyone know?

Sunday, September 20, 2015

Junk 2006 iMac repair - Part 2

Continued from Part 1.

I checked around for a replacement display and ended up buying a Samsung LTN170X2-L02 (datasheet) for $25 shipped. Bargain.

Another thing the UniMac adapter comes with is a "Y cable" for the inverter since the original screen has 2 CCFL lamps while most 17" laptop displays have 1. This cable simply connects the two outputs together and the combined output to a single lamp.
I'd recommend NOT trying this with any other inverters without checking datasheets and schematics unless you're trying to fry something. It's safe with the particular inverter model used in the iMacs, NOT all inverters universally.

I had several CCFL extender cables left over from a previous buy so I used two of those to make the adapter.


So then the display arrived like this:


No apparent damage though, so I hooked it all up.

It ain't pretty but it'll do

Moment of truth!

I'll be damned. First try even. Complete with perfect example of why I hate glossy screens.

Not getting any output from the firmware was a bit alarming but it does start working after a few seconds of blackness. Never ended up messing with the EDID. I'm fine with no Apple logo or boot menu on this machine since it's only ever going to run one operating system (which coincidentally isn't even Apple's) anyway.

So now came the most annoying and time-consuming part of this whole project, if you can believe that: Mounting the display.

I wanted to use the original brackets but the holes were all in the wrong place. Not only that but the right side bracket has gaps where the new display had screw holes.. Ugh..
This is starting to sound like an ad but note that the UniMac also comes with universal brackets so for $25 it's not a bad deal considering how much trouble it saves you from... Since I'm a cheapskate though, ghetto measures it is!

Yeah.. It's not pretty. The right bracket was even more of a pain as I had to add plastic L-brackets to fill the gaps in the metal.

If memory serves you need to shim the display around 6-8mms from the left side if you're using the original brackets as a base. I did 5-6 (the nut in the picture above) and it's just ever so slightly not enough. Annoying.

Especially since it's not so bad here:

But once everything was snapped back together it moved a little bit to the left. !@#!

I already added some epoxy to keep stuff from moving so I just left it as-is. It isn't something you really notice unless you know what to look for and I actually couldn't see it when I looked at it a week later.

In hindsight I probably could've just used contact glue or double-sided foam tape to glue the display directly onto the front bezel since it weighs almost nothing. Oh well..

Total cost $55 and a few hours of my time.

Not bad for a compact Core2Duo system that's still more than adequate for email and light browsing.