sábado, 11 de julho de 2015

How to Increase RAM available to Raspberry Pi CPU or GPU


Raspberry Pi 2 has 1,024MB RAM that is partitioned between the CPU and the GPU. If the Pi is working as a headless server or the Pi desktop is being accessed via VNC (which doesn't utilize the GPU) the memory split between the two processors can be altered to assign more memory to the CPU for running applications.
  • Default GPU memory on Raspbian is set to 64MB and the minimum recommended to ensure proper operation is 16MB.
  • Pi Camera Module requires a minimum of 128MB RAM.
  • Kodi Media center requires a minimum of 256MB RAM for the GPU, to avoid choppy video playback.
To modify GPU memory to 256MB either:
  1. edit /boot/config.txt and set gpu_mem=256;
    or
  2. run sudo raspi-config and select option 8 Advanced Options -> A3 Memory Split and modify value to 256
Save the change, reboot the Pi, and enjoy the CPU memory boost!

quinta-feira, 12 de fevereiro de 2015

Can't remote access lubuntu server with Vino but connection with ssh works.

PROBLEM:

Can't remote access lubuntu server with Vino but can ssh it.

DESCRIPTION:

You open a ssh tunnel (map remote 5900 port to local 12345 port) of remote lubuntu station (ex: 192.1.1.180) at terminal client side to remote access lubuntu station.

Example to type at cmd prompt:
 ssh -L 12345:localhost:5900 user@192.1.1.180

         note: change "user" and address (192.1.1.180) with your own ID.

You open a second terminal window at client station to start vnc with cmd:
xvncviewer localhost:12345


Error msg client side:
xvncviewer: VNC server closed connection

Error msg server (the ssh terminal) side:
channel 3: open failed: connect failed: Connection refused

DIAGNOSE:

Vino-server not running

SOLUTION:

At cmd prompt type (remote server side):
export DISPLAY=:0.0
/usr/lib/vino/vino-server



Error msg:
Connected to RFB server, using protocol version 3.7
Server did not offer supported security type


DIAGNOSE:

server encryption scheme not understood client side

SOLUTION:

At the remote lubuntu server side set encryption variable to false


cmd prompt type:
gsettings set org.gnome.Vino require-encyption false

domingo, 23 de novembro de 2014

How to install pt-br language interface on Libreoffice - Ubuntu

If you have installed Libreoffice on Ubuntu and would like to change the interface language to pt-br (brazilian portuguese) do this:

CTRL-ALT -T  to open a terminal

Then issue the following command:

sudo apt-get install libreoffice-l10n-pt-br

Cheers!

domingo, 12 de outubro de 2014

Raspberry Pi na Globo News - Ferramenta Pedagógica


Como a Globo retirou os vídeos sobre este assunto do sítio deles, me parece que não é mais um assunto que eles desejam que continue a ser divulugado.  Por ser um assunto de suma importância para o ensino básico no Brasil, eu me sinto obrigado em reproduzir aqui o máximo que consegui recuperar dos registros originais.

Enquanto a tecnologia avança para sistemas cada vez mais complicados, seis pesquisadores de Cambridge, na Inglaterra, resolveram ir na direção oposta ao criar o Raspberry Pi, um computador do tamanho de um cartão de crédito. Vendido a US$ 35, ele incentiva crianças a aprender sobre programação e dominar os bastidores do mundo virtual.

A ideia surgiu em 2006, inspirada no BBC Microcomputer System, usado nas escolas da Grã-Bretanha nos anos 80 para ensinar a lógica da informática aos alunos. No BBC Micro, era possível criar os próprios jogos e, de quebra, se tornar um especialista em códigos e funções. As aulas de programação, porém, foram riscadas do currículo porque o sistema não acompanhou a evolução tecnológica.

“As crianças viam os computadores pessoais como uma caixa de Lego. Estamos tentando recriar aquela situação na qual o natural é pensar no que se quer criar com o Raspberry Pi, em vez de apenas pensar em que jogo se quer jogar”, afirma Robert Mullins, cofundador da Raspberry Pi Foundation, uma organização de caridade que não pretende lucrar com as vendas da plataforma.

Para criar um computador tão barato, os pesquisadores concentraram tudo em um único chip. Menor e mais simples, a placa-mãe traz apenas as conexões essenciais: duas entradas USB, duas saídas de vídeo (uma HDMI e outra RCA), porta para conexão de rede, um leitor de cartão e fonte. O carregador é igual ao de um celular.

Instrumento educacional

Os cientistas de Cambridge estão empenhados em fazer do Raspberry Pi uma ferramenta de educação. O problema é que as aulas de informática de hoje não incluem mais a criação de programas ou jogos, focando apenas em softwares do dia a dia. Algumas escolas britânicas, no entanto, iniciaram uma revolução. Professores decidiram ignorar o currículo imposto pelo governo e incentivar as crianças a programar usando softwares gratuitos, como Scratch e Kodu.

“Eles sabem usar o computador, mas não sabem fazer os jogos e o software no qual eles rodam. Estamos tentando lhes mostrar maneiras mais simples de fazer isso. Algumas adoram, outras vão além do esperado”, diz o professor Ian Addison.

Desde o lançamento, em fevereiro deste ano, 300 mil placas do Raspberry Pi já foram vendidas. A maioria foi adquirida por programadores profissionais, que têm ajudado a melhorar o produto. “O projeto era apenas fornecê-las aos desenvolvedores, para ajudarem a melhorar a plataforma. Mas, quando a disponibilizamos no site de vendas, recebemos milhares de pedidos em poucas semanas”, conta Mullins.

Múltiplas aplicações
A placa conquistou os inventores e começou a ser incluída nos projetos mais diversos, como gerenciamento de mídia e criação de música. O entusiasta Dave Akerman mandou o Raspberry Pi para o espaço em busca de belas imagens, que eram transmitidas ao vivo pelo minicomputador.

Mas o Raspberry Pi não é apenas um instrumento para dar asas à imaginação. Alguns empreendedores querem usá-lo para lucrar com produtos feitos a partir dele. Não é necessário pedir nenhuma autorização especial ou licença. A única exigência é que, no pacote, o fabricante inclua o nome da placa e, se as vendas forem um sucesso, os desenvolvedores considerem doar uma pequena parte dos lucros à fundação de Cambridge.

Quem não é profissional, pode usar a ferramenta da mesma forma. O Raspberry PI traz dois softwares de programação: o Scratch, para alunos de 6 a 8 anos, e o Python, para quem já chegou a um nível mais avançado.

“Acho que se aprende muito sobre o que é um computador e o que é a ciência da computação quando se aprende a programar. Basta deixar as crianças serem criativas e inovarem com a tecnologia, dar a elas as habilidades básicas e deixar a imaginação correr solta”, acredita Mullins.

Raspberry Pi no Brasil

Colocar a mão em um Raspberry Pi requer paciência. A procura é tão grande que os distribuidores têm dificuldade de dar conta da demanda. A entrega pode demorar mais de três meses. No Brasil, a placa custa US$ 85 por causa dos impostos. Nem a demora e o preço fizeram o engenheiro eletrônico Rafael Gustavo desistir de comprar a plataforma. “O que impressiona na placa é a proposta de ter um computador muito poderoso por US$ 35. É um custo bastante baixo", diz o brasileiro.

O projeto ainda não atingiu sua principal meta: invadir as escolas e convencer as crianças de que programar é divertido. “O objetivo é criar uma geração de pessoas confiantes e que possam controlar e manipular o mundo digital, em vez de apenas consumir passivamente o conteúdo”, afirma Mullins.

REF:
http://g1.globo.com/globo-news/noticia/2012/10/cientistas-criam-computador-para-ensinar-programacao-criancas.html

quinta-feira, 11 de setembro de 2014

How to set logic levels in LTSPice to 5 volts?

LTSPICE IV - How to...

How to change logic levels in LTSPice?

Right-mouse-click on the device in your schematic.

A dialog will be shown.

Enter the parameter(s) into any of the fields
from "Value" to "SpiceLine2".

Vhigh=5 Vlow=0 Ref=1.5
Trise=5n Tfall=5n Td=5n

"Ref" is the threshold. Default is (Vhigh+Vlow)/2


Don't connect anything to unused inputs!

domingo, 7 de setembro de 2014

Reasons I Love Linux


I've have used in the past years AppleDOS, Windows 3.11, 98, XP, 7 (x32 and x64) and 8.1, Linux (many), SunOS Solaris, HP UX (Unix), OS2, IBM MVS, OS/360 - you name it, I've had my time on all of them at many moments of my working or private life.

I have also tested Linux distribuitions since the very beginning, Slackware, Debian, RedHAT, Suse, Lubuntu, Ubuntu, etc.  We used to buy magazines with a bundled CD/DVD-ROM that offered the Linux version for local install.  At that time Internet was only available in academic, companies or research centers.  Most of us used dial-up landlines to a local BBS.  The trend was to get your win-modem to work with Linux.

My very favorite operating systems for some time now, is Ubuntu Linux. Here's why:

1. Open Source and free to use. You can install it on as many computers as you like for the pretty price of absolute what you want to donate, or zero if you cannot spare some cash for now! This makes it wonderful for those on a budget, students and who get tired of constantly paying for expensive operating system upgrades.

2. It is the most stable OS that I have tested these last 30 years. I've put my kid on Windows boxes in the past only to have him mangle the operating system beyond recognition in a few short minutes. I've then put the same kid on an Ubuntu Linux box and left him playing happily for hours. 'Nuff said.

3. It's “wife” proof, that means, my wife, who is a lawyer, and does not like technology, does not call me so often like when she was using struggling with Windows, say goodbye to "my files are gone!", “updates bugs”, “virus alerts”, “BSOD”, “bad drivers”, etc.

4. Usually no Viruses or Malware. There aren't currently very many pieces of malware around for Linux boxes.  The way Linux is designed makes it very difficult for the bad guys to design malware or to crack it. As a result I don't have to bother wasting my precious computer resources on expensive antivirus programs, or having to recover my wife's or kid's system every week, hurray!!!

5. Your desktop graphics interface is a selection that can be: Unity, Gnome, LXDE, or other options of very easy to use GUI . In many ways the ease of use reminds me of the Mac computer concept when it hit the market back at the 80's but without the high price tag.

6. I can keep using my older computers as long as I want with Linux. Not only are upgrades free but the resource requirements are low enough that even older computers can use lighter versions like Lubuntu (i.e. just to mention on option), so I don't have to stop using a computer until I am ready to move on to a new one.

7. There are many open source packages that are GPL, GNU, free or pay as you need it, software available for most of all your needs.  You name it, Ubuntu has it, probably for free. They have Photoshop equivalents (Gimp), Office suite (Libreoffice), programs to see your images, hear your music, see all video types and decode streams with programs like VLC (ie. Players ) and more games (both educational and same really hot) than I have ever seen! There are programs available for Linux for literally ALL age groups and needs.

8. You can continue to use your many DOS, Windows 98 or XP, codes with WINE which runs windows codes right on you Linux screen. I use it to run LTSpice engineering circuit simulation and AXDecrypt for my confidential documents.

9. It is very powerful but at the same time very simple once you get basic “know how” of the system. While I can do almost everything I want to in the GUI, if I want to do something more complex I can always drop down to the command line and take care of business, because now I have "the power" with bash, python, C, and many other compilers and builtin tools.  For instance, I can navigate my mouse to the menu to shut down my Ubuntu computer or I can open a terminal and type "sudo shutdown -h now" or even "sudo poweroff"  at the command to turn the system off.  Ubuntu will ask me for my password and then shut the system off faster than the GUI menu ever though of doing!

10. No worries about NSA spying on you with backdoors. It is a known fact that the NSA is trying to spy on everyone. Chances are they have backdoors built into both Windows OS and applications and even on Apple computers that enable them to keep us all under surveillance. Since the source code on these operating systems is closed (some Apple Mac OSX source code is open, however), users have no way of knowing just how secure their computer really is. With Ubuntu, the source code is open so programmers all over the world look through the code to prevent these backdoors in Ubuntu.

11. It is usually easy to install hardware in Ubuntu (i.e. with exception of win-modens and some less known printers).  Plug in your printer and in moments Ubuntu has installed it. The same goes for wireless cards and many other devices commonly available. But hunting for drivers can be an issue some times, but installing bulky software or dealing with nag screens harassing you to register is gone. Most things just work, which makes life so much easier. Even my favorite old bed scanner that was dead because of lack of the right drivers for Windows 7 returned to life in Ubuntu! Yes!!!

12. A very big community of mostly friendly users, like me, with many thousands of web knowledge pages with “Howtos”, “instruct-ables”, “blogs”, “wikis”, shared experiences of almost any problem you can encounter in your life with Linux.

13. These are just same cool facts about my life before and after Linux. Let's face it, you need to be committed to get in to a better understand the Linux ways, but it is something rather FUN taking control again of your computing experience, like in the first years of home computers (ie. Sinclair, Apple II, TRS-80, Commodore, etc). Few things are as enjoyable as turning on your computer and hearing the gasps when you don't boot up Microsoft Windows.

Sure you may have to learns to answer new questions, learn a new GUI, but doing so not only spreads the word about this great operating system and also help someone to save a computer that they would otherwise throw away or loose the opportunity to “discover new worlds and boldly go where no user has gone before!”

Cheers!

terça-feira, 1 de julho de 2014

How to logout from Skype from all devices and remote places

This status problem, being offline and showing online, is often-reported in the Skype Community, after M$ took over the company, and is apparently a side-effect of having off-line instant message delivery instituted and having Skype account connected to M$ account.

The work-around I found online, until a fix is released, is to ensure my on-line/off-line status is set to "Invisible" prior to signing out of Skype, and avoid connecting to M$ account.  So far, this has worked for me.

What are chat commands and roles?

When you open a "chat" with one person in your contact list, you can use it to enter special commands to control some functions and members in the chat, secure the chat with a password and do other administrative tasks.

To see a list of the available commands simply type /help into the "chat" reply line. If you are just in a chat with one other person, only the relevant chat options will be shown. If you are in a chat with two or more people, /help will reveal a more comprehensive list of chat commands. If you don’t see the list, the version Skype you are using is not supported.

Important: Make sure you are using the latest version of Skype (only if you really needed them) because some of these commands may not be supported in older versions.

Note: you don’t need to use square brackets around your text after the command. For example, the command:

 /topic [text]

would be used as:  /topic Today’s Meeting Agenda.


Here is a list of all common commands and their descriptions:

Command Description
/add [Skype Name] Adds a contact to the chat. For instance: /add alex_cooper1 will add that member to the chat.
/alertson [text] Allows you to specify what needs to appear in a chat for you to be notified. For example, /alertson London will only alert you when the word "London" appears in the chat.
/alertsoff Disable message notifications.
/clearpassword Removes the password security.
/find [text] Finds specific text in a chat. For example, /find Charlie will return the first instance of the word "Charlie" in the chat.
/get allowlist Details people with access to the chat.
/get banlist Details people banned from the chat.
/get creator Details the person who created the chat.
/get guidelines See the current chat's guidelines.
/get options Details active options for current chat - see /set options below for a list of the options available.
/get password_hint Get the password hint.
/get role Details your role in the chat.
/get uri Creates a URL link that other people can use to join the group chat.
/golive Starts a group call with other participants of the chat.
/info Details number of people in chat and maximum number available.
/kick [Skype Name] Eject chat member. For instance, /kick alex_cooper1 will eject that member from the chat.
/kickban [Skype Name] Ejects chat member and prevents them from rejoining chat. For instance, /kickban alex_cooper1 will eject that member from the chat and ban them from rejoining.
/leave Leave current group chat.
/me [text] Your name will appear followed by any text you write. For instance, /me working from home will cause the phrase "working from home" to appear next to your name in the chat. You can use this to send a message about your activities or status.
/remotelogout Sign out all other instances except the current one. This will also stop push notifications on all other instances.
/set allowlist [[+|-]mask] .. Sets the members allowed in the chat. For instance, /set allowlist +alex_cooper1 will allow that member to join the chat.
/set banlist [[+|-]mask] .. Sets which members are banned from the chat. For instance, /set banlist +alex_cooper1 will ban that member from the chat. /set banlist -alex_cooper1 will allow them to rejoin it.
/set guidelines [text] Set a chat’s guidelines. For instance, /set guidelines No spoilers! These can be returned to be viewed in the chat by the command /get guidelines.
/set options [[+|-]flag] Sets options for this chat. For example: /set options -JOINING_ENABLED switches off the JOINING_ENABLED option, while /set options +JOINERS_BECOME_APPLICANTS will switch on the JOINERS_BECOME_APPLICANTS option.
The available flags are listed below:
HISTORY_DISCLOSED - Joiners can see the conversation that took place before they joined. The limit that they can see is either 400 messages or two weeks of time, depending on which is reached first.
JOINERS_BECOME_APPLICANTS - New users can join the chat, but cannot post or receive messages until authorized by a CREATOR or MASTER (see the table below for more information on roles).
JOINERS_BECOME_LISTENERS - New users can receive messages but cannot post any until promoted to the USER role.
JOINING_ENABLED - New users can join the chat.
TOPIC_AND_PIC_LOCKED_FOR_USERS - Only a user with a CREATOR role will be able to change the topic text or accompanying picture for the chat.
USERS_ARE_LISTENERS - Users with a USER role will be unable to post messages.
/set password [text] Create a password (no spaces allowed).
/set password_hint [text] Create the chat's password hint text.
/setpassword [password] [password hint] Create a password and password hint for the chat.
/setrole [Skype Name] MASTER | HELPER | USER | LISTENER Allows you to set a role to each chat member. A description of roles is given in the table below.
/showplaces Lists other instances where this Skype name is currently signed in.
/topic [text] Changes the chat topic.
/undoedit Undo the last edit of your message.
/whois [Skype Name] Provides details about a chat member such as current role.

Chat roles depend on whether you started the chat or were assigned a role by the chat creator or host:
Role Description
Creator The member who created the chat. There can be only one creator per chat. Only the creator can promote other members to masters.
Master Also known as chat hosts. Masters cannot promote other people to masters.
Helper A semi-privileged member. Helpers will not be affected by the USERS_ARE_LISTENERS option. Helpers cannot promote or demote other members.
User A member who can post messages into the chat.
Listener A member who can see messages but not post into the chat.
Applicant A member waiting for acceptance into the chat. Note: once accepted into the chat, members cannot be demoted to applicants.