Sunday, December 13, 2015

Dell Vostro 3350 problems upgrading to Windows 10

To get to Windows 10 appeared not an easy and straightforward task on Dell laptop. I chose upgrading from Windows 8.1 but not making a clean install. Can not comment on fresh install but upgrading made problems.
Process started as usually. Double clicking Windows 10 upgrading icon at the desktop clock. Everything went smoothly but during the process close to completing laptop screen went black. Computer was responding and it can be decided by looking on HDD light blinking and also Caps Lock light toggling. Thanks to googling I found recipe that helped.
  • First what you must do is connect external monitor to VGA output socket. You must be able to see login screen. Log in yourself.
  • Than connect to Internet and go to and download latest BIOS update for your machine. I updated to A09, but when writing this also found that A10 is available. I suppose this is not critical, just use latest one.
After restart you should see picture on both screens.

Both Windows are 64 bit versions.
Before I was testing different drivers for Intel HD Graphics 3000, newest one and some older, but what actually helped was this BIOS update.
You can also get picture on laptop's screen manually selecting Basic Graphics Drivers, but this is not good solution because you can't use maximum resolution also other features like external monitor connection etc are disabled.

Tuesday, November 10, 2015

CRC calculation in C

Here are some useful Internet resources when you have to deal with CRC calculation and checking. I found them handy and use occasionally. Some are online calculators, some gives also technical descriptions.
Below is some real working C source code. Borrowed from here!
It is tested and working. It calculates CRC CCITT16 with starting value 0xFFFF. It might be not as fast as table based CRC calculations, but occupies less RAM and code space which sometimes is essential for embedded systems.

#define POLY 0x1021

unsigned char i;
unsigned int crc = 0xFFFF;

while (wLength--) {
    wCrc ^= *(unsigned char *)pData++ << 8;
    for (i=0; i < 8; i++)
        wCrc = wCrc & 0x8000 ? (wCrc << 1) ^ POLY : wCrc << 1;
return wCrc & 0xffff;

Friday, November 6, 2015

uVision UDAS debugger connection problem

Recently I was getting strange error when trying to debug sample software on Infineon XC800 Starter Kit. Previously it was all ok, but now I got error messages in uVision output window:

Searching for DAS Server 'UDAS'...
DAS Server 'UDAS' is installed.
DAS Server 'UDAS' is not started yet. Trying to start it now...
DAS Server 'UDAS' has been started successfully.
Warning: Unknown JTAG ID=00000000. Assuming an XC866-4FR device with 16K flash

 I struggled for a while with the same problem but without success. Finally decided to search Internet and found some guidance here. I decided to switch mini-USB cable and problem disappeared immediately. Apparently I was using some random cheap low quality cable this time. Took another good thick cable and everything was fine.

Some lesson to learn. Always use good cables and check Internet after a moment if you are not succeeding to resolve problem soon.

Wednesday, July 8, 2015

Repair of Samsung laptop AC adapter model CPA09-004A

Sister has got a Samsung RC520 laptop. And this laptop power supply has got some functionality problems since bought. From time to time it stopped charging laptop and green LED light in adapter case went off. Than it was discovered that pulling off mains plug and plugging back in socket resolves issue. But unfortunately problem got more sever and after a while this procedure above did not help anymore. As the warranty period was over I decided to try to repair it.

AC adapter model name is CPA09-004A and it is made by Chicony Power Technology company. While opening adapter plastic case with knife I was thinking about possible problems what could made such fault symptoms. I was suspecting some loose soldering connection or something else but easy to fix. After opening and removing shields and rubbing away glue spots first thing I noticed was missing solder on one side of zero ohm resistor.

Red arrow shows resistor pad which is missing solder
It is always good to start electronic equipment repair with close look and inspection of device. It can save a lot of time.
So this situation with partly soldered part of course was suspicious already. After closer look it shows that resistor is series connected with optocoupler. And it explains device fault symptoms. When resistor looses connection than PWM driver are not getting feedback signal and shuts itself down. Removing and reapplying mains voltage restarts driver IC.
Than I properly soldered the resistor and connected the power supply to mains. And problem was gone of course. It can be seen also by looking on green LED which was steady and bright.
I don't know how likely is that somebody of you can meet the exact same problem on your AC adapter, but it tells something about Chicony manufacturing quality control. If you have the same product and it needs repair start with close visual inspection and look for loose connections, solder joints and similar easy things first.
And remember to be cautious when connecting power supply PCB to mains voltage without enclosure, because it is dangerous. If you are not sure what are you doing better leave repair to electronics repair service professionals.

Wednesday, May 27, 2015

Favorite IDE font

Today I selected new favorite font for my current IDE. It is called Consolas. It is quite nice good looking, monospaced and also clearly visible on screen. I use it of size 11. I have used it half a day and so far I am happy with it.

Monday, May 11, 2015


It took me several minutes to realize how to resolve this problem when you try to load your application into MCU and debug. It happens when you make some changes in the code, build it and after that start to debug. Apparently happens that situation that build in your computer is different from that one that is in the MCU flash memory as the following message tell us.

Error message is following:
Please download the application into ROM.

I did not realize what is the problem immediately and googling this lead  to some wrong hints about missing header files. Actually it is very easy to make this problem go away. In the Keil uVision go to menu Flash -> Configure Flash Tools -> in the "Utilities" tab enable check box "Update target before Debugging"