Lenovo T500: measuring screen flickering

Lenovo T500 was one of the first laptops with LED backlight. I've used also R500 with CCFL and I would actually prefer it over T500. R500 had more natural colors (no bluish hard to correct hint like with T500) and I hadn't noticed any screen flickering. With T500 flickering is quite noticeable when e.g. moving fingers before the screen.
How bad is it?
To measure actual flickering frequency I've connected small photovoltaic battery from old calculator to USB oscilloscope input (1M input impedance) and put 100k load resistor in addition.

T500 has 16 brightness levels, here are some captured waveforms from photo cell in front of the screen:
lowest brighness (aka level01): 100Hz pulse period

level02: similar amplitude captured (pulse width) but 220Hz pulse frequency

level05: higher amplitude (probably wider pulse), same frequency

level 10


level14: roughly 50% pulse width

level15: pulse width over ~66%, same frequency (still 220Hz)

level16 (brightest): no flickering


GPS-400AB power supply

DELTA GPS-400AB power supply, branded as ASUS. Some sources point that same power supply can be also sold under Chieftec or Enlight brand. This unit seems to be produced in 2008.

"Cigarettes, that's what got her".

 Most of the capacitors branded as CapXon are either leaked or about to burst.
 This is why this power supply is heavy -  passive PFC choke, PFC41V-056 TP130-2.
Most individual wires are crimped in groups, copper crimps are soldered to PCB.
 From what I can find DWA102 seems to be analog of TPS5510P, 3-channel power supervisor (over/undervoltage protection).
 U8KBA80R - 800V, 8A rectifier
 These soldered and then cut out resistors seems to be some kind of configuration elements. As markings say same PCB is used for GPS-300AP and GPS-350AP (AB?).

 Quite a lot components on the bottom side.

 Soldering is slightly inconsistent, as if few componets were manually soldered.

TL431AC - voltage reference in TO-92 package - 2 pcs
transoptors: PC123 - 3 pcs
STPS2045CT (dual 10A Schottky) - 4 pcs


EmBitz - first impression

EmBitz is Code::Blocks based pre-packaged IDE with ARM compiler targeted for embedded.
It is relatively lightweight (50MB installer including GCC), ~600MB after installation. Obviously it's also much more responsive than any eclipse-based IDE.
IDE works with STLink and it looks like it's much more stable than SW4STM32 (when working with SW4STM32 I had to reset/reconnect STLink each 5 minutes, so far I haven't seen any problems with EmBitz.
While collection of .svd files is available only after buying support package it seems that .svd files from other sources work as well.



When you are looking for crappy software, Microsoft can provide. I'm not not talking about Windows as Linux desktop distributions I've tried recently failed me way worse, often with functionality broken right from the start (i.e. it seems to me that no one tests it before releasing, not even once). But when it comes to overly complicated and bloated non-os software Microsoft is definitely the leader.
Last year I've installed Visual Studio 2015 Community and I just discovered that it has a habit of eating disk space on system partition, 10MB (some installer file with random name and some log file) every day with update installation that fails:
2017-03-17 08:26:21 - Microsoft VSIX Auto Update
2017-03-17 08:26:21 - -------------------------------------------
2017-03-17 08:26:22 - VSIXAutoUpdate :  Supported products on the machine
2017-03-17 08:26:22 -         Microsoft Visual Studio Community 2015
2017-03-17 08:26:22 - VSIXAutoUpdate :  Supported products applicable to auto update
2017-03-17 08:26:22 -         Microsoft Visual Studio Community 2015
2017-03-17 08:27:17 - VSIXAutoUpdate result in error when updating extension:
2017-03-17 08:27:17 - xxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxx-Developer Analytics Tools-
2017-03-17 08:27:17 - Certificate check failed. Certificate information of the previously installed extension could not be read.

I hope that disabling VSIX Auto Update in Task Scheduler would stop this.


Logitech M310

Since replacement mouse wheel encoder for my A4Tech X-710 turned out to be almost as imprecise as old one and it's USB cable has lost almost all isolation exposing wires (I guess chemical decomposition over time) and plastic cracked a little next to screws it's time to change mouse.
I've bought refurbished Logitech M310 for $12.
First impression:
  • it's "full size" mouse and it turns out it's very similar in size and shape to X-710
  • left and right button are nice but little louder than in A4Tech
  • middle/scroll button is slightly hard to use requiring some force to be pressed and pretty loud
  • scroll wheel moves quietly and with little resistance although still seems to be precise (contrary to opinions I've found on micro-precise scroll used e.g. in M325)
  • off-center optical sensor probably needs some time to adjust to (sensor in X-710 was placed exactly in the middle)
  • mouse feet seem interior to those (thicker and 6 instead of 4) in X-710
  • mouse worked out of the box (I'm not sure if paired earlier or does not require pairing), no software installation was necessary with Windows 7 
Because of asymmetric optical sensor location I wouldn't recommend it for people using left hand (or both hands) - when using with right hand it feels like it has lower dpi than X-710 (i.e. less than 1000) while using with left hand it behaves very strange. It must be related to anatomy - when rotating mouse with right hand cursor moves only a little (this is fine) while when rotating even little with left hand cursor moves whole screen length.
If you are using windows consider turning off "Allow this device to wake up the computer" option in device manager to not be surprised with accidental waking up of computer. Useful commands:
  • powercfg lastwake - check reason of last wakeup
  • powercfg -devicequery wake_armed - list devices allowed to wake PC
Although producer recommends alkaline cell (i.e. 1.5V cell) it works fine with charged NiMH eneloop 2000mAh cell. With my use (5-6 hours on work day, more on weekends, no ON/OFF switch used) it worked 2.5 months from this cell, down to 0.945V.

I am not noticing optical sensor performance drop after switching from X-710 which is probably good thing. I'm using cloth mouse pad thus these are not challenging conditions though.