2017-06-10

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

level13

level14: roughly 50% pulse width

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

level16 (brightest): no flickering

2017-05-23

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).
 UC3843 
 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.

Other:
TL431AC - voltage reference in TO-92 package - 2 pcs
transoptors: PC123 - 3 pcs
K3767
W9NK90Z 900V 8A MOSFETs
STPS2045CT (dual 10A Schottky) - 4 pcs

2017-04-01

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.

2017-03-25

VSIXInstaller

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-7.18.214.2
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.