🗊Презентация Serial Communications

IMPLEMENTING IOE Assist. Prof. Rassim Suliyev - SDU 2017

Communicating with Others Arduino can use same USB cable for programming and to talk with computers Talking to other devices uses the “Serial” commands TX – sending to PC RX – receiving from PC

Serial Communications Sends “Hello world!” to your computer Click on “Serial Monitor” button to see output

Arduino Communications Is just serial communications Arduino doesn’t really do USB It really is “serial”, like old RS-232 serial All microcontrollers can do serial Not many can do USB Serial is easy, USB is hard

Serial Communications “Serial” because data is broken down into bits, each sent one after the other down a single wire. The single ASCII character ‘B’ is sent as:

Arduino & USB-to-serial A standard Arduino has a single hardware serial port But serial communication is also possible using software libraries to emulate additional ports

Arduino Mini Arduino Mini separates the two circuits

Arduino Mega The Arduino Mega has four hardware serial ports Only one of these has a USB adapter built in

Arduino to Computer USB is totally optional for Arduino, but it makes things easier Original Arduino boards were RS-232 serial, not USB All programs that talk to Arduino (even the Arduino IDE) think that they’re talking via a serial port

Arduino & USB Since Arduino is all about serial, and not USB, Interfacing to things like USB flash drives, USB hard disks, USB webcams, etc. is not possible Also, USB is a host/peripheral protocol. Being a USB “host” means needing a lot of processing power and software, not something for a tiny 8kB microcontroller. It can be a peripheral. In fact, there is an open project called “AVR-USB” that allows AVR chips like used in Arduino to be proper USB peripherals

Serial Message Protocol Where each message begins and ends? Sides must agree how information is organized in the message (communications protocol) Header - one or more special characters that identify the start of message Footer - one or more special characters that identify the end of message

Sending Debug Information from Arduino to Your Computer This sketch prints sequential numbers on the Serial Monitor:

Baud rate

Sending information You can display text using the Serial.print()or Serial.println() function

Strings String message = "This string"; //C++ type strings message.length() //provides thenumber of characters) in the string message.concat(anotherMessage) //appends the contents of anotheMessage to message (also + operator) message.substring(s, e); //returns a substring starting from s till e You can use the indexOf and lastIndexOf functions to find an instance of a particular character in a string char message[8] = "Arduino"; //C type string int length = strlen(message); // return the number of characters in the string strcpy(destination, source); // copy string source to destination strcat(destination, source); // append source string to the end of the destination string if(strcmp(str, "Arduino") == 0) // do something if the variable str is equal to "Arduino"

Comparing C type Strings

String Object charAt(n) or [n] - Access a particular character of the String concat(parameter) or + - Appends the parameter to a String endsWith(string2) - Tests whether or not a String ends with string2 equals(string2) or == - Compares two strings for equality (case sensitive) indexOf(val, [strt]) – locates val in a String by searching forward starting from strt index. To search backward use lastIndexOf(val,[strt]) length() - Returns the length of the String, in characters remove(index,[count]) – remove all characters (or count caracters if given) from a String starting from index replace(substring1, substring2) – Replace all instances of substring1 in a String to substring2 setCharAt(index, c) - Sets a character to c at index of the String startsWith(string2) - Tests whether or not a String starts with the string2 substring(from, [to]) - Get a substring of a String, from - inclusive, to – exclusive toInt() or toFloat() - Converts a valid String to an integer or float toLowerCase() or toUpperCase() - Get a lower-case or upper-case version of a String trim() - Get a version of the String with any leading and trailing whitespace removed

Mathematical Operators

Comparing Character and Numeric Values

Logical and Bitwise operators Logical operators Bitwise operators

Combining Operations and Assignment

Advanced Mathematical Operators

Other Useful Operators

Functions Functions are declared by first declaring the function type. This is the type of value to be returned by the function such as 'int' for an integer type function. If no value is to be returned the function type would be void. After type, declare the name given to the function and in parenthesis any parameters being passed to the function.

Receiving Serial Data in Arduino Serial.available() - Get the number of bytes (characters) available for reading from the serial port. This is data that's already arrived and stored in the serial receive buffer (which holds 64 bytes) Serial.read() - Reads incoming serial data Serial.readBytes(buffer, length) - reads characters from the serial port into a buffer. The function terminates if the determined length has been read, or it times out

Controlling Arduino

Tasks Part 1 Concatenate two strings (Name, Surname) with space between them and output to serial monitor Find a number of spaces in a given text Given a string “Name Surname Age”, divide it to 3 strings Convert a String containing a number to a number Write function that compares 2 numbers and returns -1 if a<b, 0 if a=b, 1 if a>b Write function that returns minimum number from an array of integers

Tasks Part 2 Write function that sorts array of integers Read the number N from Serial port and make LED blink N times Read numbers N and M and return N to the power of M

Home Work Given 2 strings A and B. A contains some text and B contains a number. Print B times A. Write function that compares two c type strings Write function that returns both minimum and maximum number from an array of integers Read N from Serial port and return N’th Fibonacci number Read N from Serial port then read N numbers into array, print sorted array Read a character from Serial port and print its ASCII value Read a String from Serial port then append “-OK” to it and print the resulting string