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dB vs dBm

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dB   DB is Power Ratio OR Power Loss OR Variation in Power.  So, in order to see the loss of your patch cable, you need a transmitter at one end with known power and put the receiver on the other end with known transmitter power. Then the receiver will give you the dB or loss introduced by the patch cable you made.  dBm dBm is the actual Power of the signal or value of the quantity. Getting the Signal Strenght of an RF signal is tricky. The Most accurate way to express it is with Milliwatts (mW). But you will end with with huge number if zero in before decimal places because of super-low power. For Example -60dBm is 0.000001 Milli Watts. So that means 1mW = 0dBm , 10mW = 10dBm, 100mW = 20 dBm, -40db = 0.0001 mWatt
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Basics of Sending Data Serially in AVR (ATmega32)

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  1. Before you start serial communication you have to enable the USART receive r or USART transmitter by writing one to the RXEN or TXEN bit of UCSRB.  LDI R16, (1<<TXEN)  OUT UCSRB, R16 2. As we mentioned before, in the AVR you can use either synchronous or asynchronous operating mode. The UMSEL bit of the UCSRC register selects the USART operating mode. Since we want to use the Asynchronous USART operating mode, we have to set the UMSEL bit to zero/low. Note: By default, UMSEL is Zero/LOW, so instruction (0<<UMSEL) can be skipped  // NOTE: When Writing to USCRC if    URSEL = 1, data will go to USCRC, if URSEL = 0, Data will go to BRRH, because BRRH and USCRC share the same address. To set the number of data bits (character size) in a frame you must set the  values of the UCSZ1 and USCZ0 bits in the UCSRB and UCSZ2 bits in UCSC.  LDI R16, (1<<URSEL)|(1<<UCSZ1)|(1<<UCSZ0)|(0<<UMSEL)    OUT UCSRC...
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U-Boot SPL vs U-BOOT

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During I was Working on Embedded  Linux development, during boot up the very first message you will see on the console is as shown below. So I was curious what is U-BOOT SPL and U-BOOT. So i tried to understand this bootup process below. On Embedded OMAP platforms the first program being run after power-on is ROM code (which is similar to BIOS on a PC. This Code buried in every Microcontroller, Microprocessor by default by the manufacturer). ROM code looks for bootloader (which must be a file named "MLO" and located on the active first partition of MMC, which must be formatted as FAT12/16/32, -- but that's details) ROM code copies the content of that "MLO" file to static RAM (because regular RAM is not initialized yet). Next picture shows the SRAM memory layout for OMAP4460 SoC: SRAM memory is limited (due to physical reasons), so we only have 48 KiB for the bootloader. Usually regular bootloader (e.g. U-Boot) binary is bigger than that. So we need to create som...
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br0 Network Interface Explained

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Bridging allows you to create a software switch that connects two ports at Layer 2 of the OSI model. A bridge consists of two or more ports that are members of a bridge group. This document was created on VyOS 1.2.0. Software Switch: Similar to a Hardware switch, a software switch also works as a LAN switch and it learns the Mac address of bridged interfaces. The bridged interface can be ethernet or wifi. Bridge Interface Names Bridge interfaces are named   br  in front of a number, for example,  br0  would bridge interface zero. Bridge interfaces can be called bridge interfaces or bridge groups interchangeably. Creating a Bridge Creating a bridge interface is very simple. For this example, let's create a bridge between two physical interfaces on a VyOS router. More example use cases will be given below. This example uses  eth0  and  eth1 . vyos@vyos-rtr# set interfaces bridge br0 vyos@vyos-rtr# set interfaces ethernet eth0 bridge-group bridge br...
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