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Linux/UNIX shell commands The UNIX shell is a command-line interface made for interacting with the OS. There are various commands to execute this. Note: The current documentaiton is based on Ububtu and similar debian bases operating systems. File systems The linux file system is a tree structure with the root directory at the top. The root directory is denoted by /. The directories are separated by / and the files are separated by .. The file system is case sensitive. The file system is made up of the following: ...

Computer networks Packets In networking, a packet is a small segment of a larger message. Data sent over computer networks*, such as the Internet, is divided into packets. These packets are then recombined by the computer or device that receives them. The Internet is a “packet switching” network. Packet switching refers to the ability of networking equipment to process packets independently from each other. It also means that packets can take different network paths to the same destination, so long as they all arrive at the destination. Because of packet switching, packets from multiple computers can travel over the same wires in basically any order. This enables multiple connections to take place over the same networking equipment at the same time. ...

Motor Encoder Components Arduino Uno 4x4 Keypad I2C LCD DC Motor with encoder L293D Motor Driver Connections Display connections From (I2C display) To (arduino) 1 VCC 5V 2 GND GND 3 SDA SDA 4 SCL SCL Keypad connections From (Keypad) To (arduino) 1 Row 1 D13 2 Row 2 D12 3 Row 3 D11 4 Row 4 D10 5 Col 1 D9 6 Col 2 D8 7 Col 3 D7 8 Col 4 D4 Motor connections From (Motor) To 1 Motor negative Output 4 (L293D) 2 Motor positive Output 3 (L293D) 3 Encoder ground GND (L293D) 4 Channel B D3 (arduino) 5 Channel A D2 (arduino) 6 Encoder power 5V (arduino) L293D connections From (L293D) To (arduino) 1 Power 1 5V 2 Input 4 D5 3 Output 4 refer above 4 Ground GND (both arduino/motor) 5 Ground GND (both arduino/motor) 6 Output 3 refer above 7 Input 3 D6 8 Enable 3,4 5V 9 Enable 1,2 5V 10 Input 1 N/A 11 Output 1 N/A 12 Ground GND 13 Ground GND 14 Output 2 N/A 15 Input 2 N/A 16 Power 2 5V Code 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 // ---------- // keypad setup #include <Keypad.h> const byte numRows= 4; //number of rows on the keypad const byte numCols= 4; //number of columns on the keypad // global keypad variables String enteredValue = ""; int encoderSpeed = 0; float debugEncoderSpeed = 0.00; // (encoderSpeed * 100) / 255 //keymap defines the key pressed according to the row and columns just as appears on the keypad char keymap[numRows][numCols]= { {'1', '2', '3', 'A'}, {'4', '5', '6', 'B'}, {'7', '8', '9', 'C'}, {'*', '0', '#', 'D'} }; //Code that shows the the keypad connections to the arduino terminals byte rowPins[numRows] = {13,12,11,10}; //Rows 0 to 3 byte colPins[numCols]= {9,8,7,4}; //Columns 0 to 3 Keypad myKeypad= Keypad(makeKeymap(keymap), rowPins, colPins, numRows, numCols); // ---------- // lcd setup #include <Adafruit_LiquidCrystal.h> Adafruit_LiquidCrystal lcd_1(0); int LCDRow = 0; #define motorA 5 #define motorB 6 int encoderPin1 = 2; int encoderPin2 = 3; volatile int lastEncoded = 0; volatile long encoderValue = 0; volatile long correctEncoderValue =0; long lastencoderValue = 0; int lastMSB = 0; int lastLSB = 0; void setup() { Serial.begin (9600); pinMode(encoderPin1, INPUT); pinMode(encoderPin2, INPUT); digitalWrite(encoderPin1, HIGH); //turn pullup resistor on digitalWrite(encoderPin2, HIGH); //turn pullup resistor on attachInterrupt(0, updateEncoder, CHANGE); attachInterrupt(1, updateEncoder, CHANGE); pinMode(motorA,OUTPUT); pinMode(motorB,OUTPUT); lcd_1.begin(16, 2); lcd_1.print("Enter value:"); lcd_1.setCursor(LCDRow, 10); } void loop() { // encoder control statements correctEncoderValue = encoderValue/4; Serial.println(correctEncoderValue); if ( 0<=correctEncoderValue && correctEncoderValue < 3000) { analogWrite(motorA,encoderSpeed); digitalWrite(motorB,LOW); } else { analogWrite(motorA,0); digitalWrite(motorB,LOW); } delay(100); // keypad control statements char keypressed = myKeypad.getKey(); if (keypressed != NO_KEY) { Serial.println(keypressed); } // getting the key pressed from the user if (keypressed){ // gets triggered for numeric key presses if (keypressed != 'D' && keypressed != 'A' && keypressed != 'B' && keypressed != 'C') { Serial.println(keypressed); lcd_1.print(keypressed); lcd_1.setCursor(++LCDRow, 10); enteredValue += keypressed; // a - clear the entered value } else if (keypressed == 'A') { lcd_1.clear(); lcd_1.print("Enter value:"); lcd_1.setCursor(++LCDRow, 10); enteredValue = ""; encoderSpeed = 0; // d - update the entered value } else { LCDRow = 0; lcd_1.clear(); lcd_1.print("Value updated"); delay(500); // taking the encoder speed from the user // encoder value lies between 0 and 255 // we take the value only if its between 0 and 255 if (enteredValue == "") { encoderSpeed = 0; Serial.println("Case 1: Blank entered value"); } else if (enteredValue.toInt() > 0 && enteredValue.toInt() < 255) { encoderSpeed = enteredValue.toInt(); Serial.println("Case 2: Accepted entered value"); } else { encoderSpeed = 0; Serial.println("Case 3: Out of of bounds entered value"); } } // special keypresses end } // keypressed trigger end debugEncoderSpeed = (encoderSpeed * 100) / 255; Serial.println(debugEncoderSpeed); } void updateEncoder(){ int MSB = digitalRead(encoderPin1); //MSB = most significant bit int LSB = digitalRead(encoderPin2); //LSB = least significant bit int encoded = (MSB << 1) |LSB; //converting the 2 pin value to single number int sum = (lastEncoded << 2) | encoded; //adding it to the previous encoded value if(sum == 0b1101 || sum == 0b0100 || sum == 0b0010 || sum == 0b1011) encoderValue ++; if(sum == 0b1110 || sum == 0b0111 || sum == 0b0001 || sum == 0b1000) encoderValue --; lastEncoded = encoded; //store this value for next time } How to use this Click the link below and press simulate. You can see the debug output in the serial monitor. To enter a value press a key on the keypad. To update the value press D and to clear the value press A. ...

ARM Basics Advanced RISC Machine (ARM) is a family of reduced instruction set computing (RISC) architectures for computer processors, configured for various environments. Arm Holdings develops the architecture and licenses it to other companies, who design their own products that implement one of those architectures‍—‌including systems-on-chips (SoC) and systems-on-modules (SoM) that incorporate memory, interfaces, radios, etc. It also designs cores that implement this instruction set and licenses these designs to a number of companies that incorporate those core designs into their own products. Running ARM IC within simulator Download and install Keil uVision - MDK ARM Go to project in the menu bar anc click on new uVision Project. Select lpc2148 in the menu and click it. Disable startup file. Save the project in a new folder named something. This folder name can be changed accordingly but all the dependency file should correspnd to it. Within this folder create a newfile called as something.s. Copy and paste this code in something.s 1 2 3 4 5 6 7 8 AREA ONE, CODE, READONLY ENTRY MOV R0, #0X01 MOV R1, #0X02 ADD R2, R1, R0 L B L END Click one the source group on the left hand side and right click to add existing files… Add the something.s file, by checking the assembly files option Click translate first on the menu bar and then click build the second time. Now in the menu bar click on debug and then click start/stop debug session You can click run to run everything or click on step to run one line at a time More info about the lpc2148 The microcontroller lpc 2148 is a 32 bit memory controller. ...

Web notes FYI CSA: Client server architecture A web can be two tier, three tier, n tier having different applets for different purposes HTML: Hypertext markup lang, CSS: Cascading stylesheet, JS: Javascript P2P: Peer to peer architecture DOM: Document Object Model (DOM) is a file model wherein all the files are shown in a multiinterface structural model Tree stucture: A tree structure is a model where the start point is a single node but as we go down the model the number of nodess increase just like a tree. Misc &npsp: singlewhitespace Basics Structure of a HTML document A HTML document contents many tags called as elements. These elements are crutial in making a HTML document. This is the common structure of an HTML document. ...