Month: March 2018

Common-mode rejection ratio – Wikipedia

Jovan Stosic March 20, 2018

The common mode rejection ratio (CMRR) of a differential amplifier (or other device) is a metric used to quantify the ability of the device to reject common-mode signals, i.e., those that appear simultaneously and in-phase on both inputs. An ideal differential amplifier would have infinite CMRR, however this is not achievable in practice. A high CMRR is required when a differential signal must be amplified in the presence of a possibly large common-mode input, such as strong electromagnetic interference (EMI). An example is audio transmission over balanced line in sound reinforcement or recording.

Theory
Ideally, a differential amplifier takes the voltages, V+ and V- and produces an output voltage

V_{\mathrm {o} }=A_{\mathrm {d} }(V_{+}-V_{-})

where Ad is the differential gain. However, the output of a real differential amplifier is better described as

{\displaystyle V_{\mathrm {o} }=A_{\mathrm {d} }(V_{+}-V_{-})+{\tfrac {1}{2}}A_{\mathrm {cm} }(V_{+}+V_{-})}

where {\displaystyle A_{\mathrm {cm} }} A_{\mathrm {cm} } is the common-mode gain, which is typically much smaller than the differential gain.

The CMRR is defined as the ratio of the powers of the differential gain over the common-mode gain, measured in positive decibels (thus using the 20 log rule):

{\displaystyle \mathrm {CMRR} =\left({\frac {A_{\mathrm {d} }}{|A_{\mathrm {cm} }|}}\right)=10\log _{10}\left({\frac {A_{\mathrm {d} }}{A_{\mathrm {cm} }}}\right)^{2}{\text{dB}}=20\log _{10}\left({\frac {A_{\mathrm {d} }}{|A_{\mathrm {cm} }|}}\right){\text{dB}}}
differential gain should exceed common-mode gain, this will be a positive number, and the higher the better.

 

Source: Common-mode rejection ratio – Wikipedia

Common-mode rejection ratio – Wikipedia was last modified: March 20th, 2018 by Jovan Stosic

Does U-Center support Linux? – u-blox forum

Jovan Stosic March 17, 2018

Problem solved! Now I can run u-center 8.26 on Linux. I tried Mint and Lubuntu, both works fine. Although my laptop has Atom processor and 1G RAM, I can open many graphical windows, including Packet Console, Table View and so on. I tested by recording data for one hour, it worked fine, no crash.

I did intensive experiments with two versions of Linux, three versions of wine and two versions of u-center. They are:
Linux:
Mint 18.2 Mate //newest version, test reulst: okay
Lubuntu 17.04 //newest version, test reulst: okay

Wine:
winehq-stable 2.0.2 //newest, test reulst: okay
winehq-devel 2.13 //newest, test reulst: okay
1.6.2 //This is obtained through Software Manager in Mint. Really old version. Not recommended to use.

u-center:
8.26 //test reulst: okay.
8.16 //crash upon opening one of the three consoles: the packet console, binary console or test console. Not recommended to use.

At the time of writing, I recommend to use the wine 2.0.2 or 2.13 in combination with u-center 8.26. This issue has nothing to do with Linux distribution.
There’s crash in u-center 8.16 upon opening one of the three consoles as described above. The prompt window says:
The program u-Center.exe has encountered a serious problem and needs to close. We are sorry for the inconvenience. The can be caused by a problem or a deficiency in Wine. You may want to check the Application Database for tips about running this application.
If I click on “show details” button, a new window prompts out saying “Program Error Details: Unhandled exception: page fault on read access: 0x00000000 in 32-bit code (0x7ea213a0)……”

Here is how I did:
1. Install Mint or Lubuntu.

2. Install Wine Binary Package, following this link: https://wiki.winehq.org/Ubuntu
I chose the online method.
In case of Mint 18.2 Mate + winehq-stable package + my 32-bit laptop, here is the list of commands:

wget -nc https://dl.winehq.org/wine-builds/Release.key
sudo apt-key add Release.key
sudo apt-add-repository https://dl.winehq.org/wine-builds/ubuntu/
sudo apt-add-repository ‘deb https://dl.winehq.org/wine-builds/ubuntu/ xenial main’
sudo apt-get update
sudo apt-get install –install-recommends winehq-stable

If you want to reinstall other versions of wine package, run this command first before install other version of wine:
sudo apt-get remove winehq-stable

3. Run the command

winecfg

Unter “Application” Tab, select “Windows Version” to Win10. WinXP is default.
This step is very necessary, since u-center 8.26 doesn’t support Windows XP. If you don’t do this before install u-center 8.26, then a window will promt out saying “only windows vista or above supported”. Then Installation is aborted.
More information can be found at this website:
https://www.winehq.org/docs/wineusr-guide/config-wine-main
If winecfg command runs first time after the installation of wine, you will be asked to choose to install mono and gecko packages, just click on “yes” to install them.

4. Download u-center 8.26 and install it by default. After installation of u-center 8.26, it should be okay to launch, but communication is not yet set up between laptop and ublox.

5. Run the commands:

sudo adduser YOUR_USER dialout
cd ~/.wine/dosdevices
ls
ln -s /dev/ttyACM0 com1
sudo reboot

Note:
a) Replace “YOUR_USER” with the user name you use. This step is very necessary. If you don’t run adduser command, even if u-center can be launched, it’s not possible to choose com port, since all the ports are disabled. They appears in light gray in color, can’t be selected.
b) The second and third commands change directory to wine directory, and lists all the com ports.
c) The fourth command links the file ttyACM0 in /dev directory to com1. You may replace com1 with other COM ports. Every time you plug ublox into the USB port, the file named “ttyACM0” appears under the dev directory. Someone uses “ttyUSB0” instead of “ttyACM0”. But in my case it’s “ttyACM0”.
d) Restart the computer is necessary. Otherwise the adduser command will not take into effect. If you just restart the u-center without reboot computer, the com port is still unavailable to select.

I’ve experienced that after execution of the second and third commands, there were already 32 com ports in the directory, i.e. com1 to com32. What I did is: unlink one COM port, e.g. unlink COM1 by the command:

unlink com1

then link com1 with the ttyACM0 file by the command:

ln -s /dev/ttyACM0 com1

6. After reboot, laptop should be able to communicate with ublox via USB. Setup finishes.
penguin007 answered Jul 29, 2017
penguin007 edited Jul 29, 2017 Flag Flag Comment

Source: Does U-Center support Linux? – u-blox forum

Does U-Center support Linux? – u-blox forum was last modified: March 17th, 2018 by Jovan Stosic