USB Physical layer and components description

USB

USB Physical layer and components description USB 1.0 – Low speed –  1.5Mbps USB 1.1 – Full Speed  –   12 Mbps USB 2.0 – High Speed  – 480 Mbps USB 3.0 – Supper Speed – 3.2 Gbps Bus Topology Refer. Sec 4.1.1 – USB 2.0 spec Due to timing constraints allowed for hub and cable … Read more

Understanding Linux Device Tree Syntax (DTS)

DTB = Devicetree blob. Compact binary representation of the devicetree.DTC = Devicetree compiler. An open source tool used to create DTB files from DTS files.DTS = Devicetree syntax. A textual representation of a devicetree consumed by the DTC. See Appendix A Devicetree Source Format (version 1) A boot program (bootloader) loads a devicetree into a … Read more

How to capture Bluetooth packets on Android ?

Bluetooth

When we want to capture bluetooth packets for some debugging in Android, we can follow below procedure. Enable Bluetooth and then make sure you have also enabled developer options. Go to developer options, and enable “Enable Bluetooth HCI Snoop Log” then do the operations of what you need to capture from bluetooth, Now, connected your … Read more

adb shell command to Turn ON Bluetooth & make it discoverable

bluetooth

We can turn on the Bluetooth using adb command as below, once you type this on your desktop/laptop, Android will prompt the user on Mobile / Android device for allowing permissions to turn ON the bluetooth, like below We can make the Bluetooth Discoverable using adb command as below, This will prompt user on android … Read more

Writing first Linux kernel Module

We will try to understand the simple kernel driver which initially we will compile for Ubuntu host and later for a embedded hardware. Create a Makefile, [Note: Make sure you have added TAB before “make” in above makefile ] Now, compile this kernel module for Ubuntu based host, The “tree” command shows the output files … Read more

How to Enable and Disable Wireless / WiFi from command line ?

Rfkill is a tool for enabling and disabling wireless devices. We use “rfkill list” command as below to check the list of available wireless devices on our machine. This command returns the devices and its index 0, 1, 2 as below, As seen above we have a WiFi, LAN and Bluetooth supported and ON in … Read more

How to Turn ON and Turn OFF Bluetooth from command line ?

Rfkill is a tool for enabling and disabling wireless devices. Using “rfkill list” command we first check the list of available wireless devices supported in our hardware as, As seen above we have a WiFi, LAN and Bluetooth supported and ON in my laptop. Now lets try turning ON & OFF this Bluetooth device using … Read more

How to extract files from jffs2 root filesystem image ?

[ Note: following commands has been tried on ubuntu 16.04, but should work on other Linux distros as well ] Lets create a temporary device node in /tmp as, brw-r–r– 1 root root 31, 0 Aug 23 00:21 /tmp/mtdblock0 Now lets use dd command to write jffs2 binary rootfs to temporary device node we created … Read more