Command to test audio in rasberry pi

speaker-test -c 5 - t wav

HOW TO AUTOSTART A WEBSITE IN FULL SCREEN MOD IN RASPBERRY

By default, the System autostart is applied to all users and executes each time a user logs in.
The System autostart file is located here: /etc/xdg/lxsession/LXDE-pi/

1)sudo nano /etc/xdg/lxsession/LXDE-pi/autostart

2)paste the below given command

@lxpanel --profile LXDE-pi
@pcmanfm --desktop --profile LXDE-pi
@xscreensaver -no-splash
@chromium-browser --kiosk https://www.google.com/
To save and exit the nano editor press CTRL-X, Y and then ENTER. You can use your preferred text editor if nano isn’t your first choice.

• The first 2 lines are important and must not be removed and must also be present if doing the User method. If you have made an autostart file without these lines, the desktop will boot to a blank (Openbox) screen. To recover, right click anywhere on the screen and select terminal from the menu. Then edit autostart and add those 2 lines.

• The xscreensaver command is only relevant if you have installed xscreensaver. If not then it can be removed or just ignored.

• The @ is optional. With @ present, if there is an error on first try, the system will attempt to run the command up to 4 more times before giving up.

• Note that the autostart file is not a bash script and is processed differently. The commands in the autostart file are processed independently at near the same time in a parallel fashion. Or the system does not wait for the previous command to complete before starting the next command. If you have multiple commands that are dependent on being run in a specific order then you would need to put your commands in a bash script, then call your bash script from autostart.

• All programs launched by autostart run in the background so no need to use & at the end of the command.

• It is important to use the complete paths to scripts in autostart. Also calls within a script need to have the complete path specified. Paths to installed apps are not required.

• Scripts must be made executable.

• If your script requires keyboard and/or console interaction, then use the lxterminal -e command. See examples and notes below.

• If your command or app requires network and does not seem to work from autostart, then try enabling the wait for network at boot option in sudo raspi-config

• In some rare cases you may need to add a delay before starting your script to give the Desktop more time to complete the booting process before your app starts. This can be done with a bash sleep command. Do not attempt to add the sleep command directly in autostart, it won’t work. Use the sleep command in a bash script instead.

3) sudo raspi-config

go to advanced ->wayland-> and  change option to X11

The autostart file doesn't work because the new OS runs wayland as a backend, not X11. I'm sure there is a better solution, using the new wayland backend, but mine is just switching back to X11, then the autostart file works again. You can do so in the "sudo raspi-config" menu and then selecting advanced options > wayland.

How to edit the network setting in raspberry

 The following command can be used to load the file into an editor update the file:

sudo nano /etc/dhcpcd.conf

Home automation system using HC-05 Bluetooth module with Arduino Nano

 Using HC-05 Bluetooth module and Arduino nano making home automation system which can be controlled by smartphone

Components 1.Arduino nano 2.hc-05 Bluetooth module 3.4 Channel relay module 4.blanck PCB 5.Jumper connectors

source  code and cicuit diagram are on below link 

https://drive.google.com/drive/folders/1qzzS5Ps_Umg_29Gzq99c8AzmqrKPKPqy?usp=sharing

How to take a screenshot in raspberry

1)install this application by pasting the below given command

 sudo apt-get install scrot

2) after installing (scrot) by applying this command in terminal you can take a screen short instantly

3)if you want to take a delayed screen short the you can apply this command(scrot -d 10 )

****all your screen shot images will be saved in home folder****

GPIO control commands using terminal

1) (gpio readall) using this command you can read the stratus of gpio pin status

2)(gpio -g mode 22 out)this command helps to on the gpio pin

(gpio -g mode 22 in)this command helps to off the gpio pin

where 22 is number of gpio pin you can change the pin number which you want to control

3)below given picture will help to find and analyse gpio pins

how to open a folder in raspberry with root permission

1)open the folder which you want to access as root user

2)goto tools-----------open current folder in terminal

3)type this command in terminal (sudo pcmanfm)and press enter

4)same folder will open age now you can edit,delete,or do any modification