Assignment:

Design and build a wired &/or wireless network connecting at least two processors.

Let’s go to Communicate!

Concept:

The   Slave   board   is   waiting   for   command   and   blink   ...   so   the   master   board generate   at   random   command,   number   1   for   led   power   on   and   2   for   led power off, and send it to slave by serial port.

Final Result:

The   video   on   right   side,   demonstrates   good   working   of   boards   and   software everything's made by me thanks to  knowledges learned by Fablab course.

Communication: Serial Asynchronous Interface

Serial   interfaces   stream   their   data,   one   single   bit   at   a   time.   These   interfaces   can   operate   on   as   little   as   one   wire,   usually   never   more than four. Serial Generalization: Example of a serial interface, transmitting one bit every clock pulse. Just 2 wires required! Asynchronous   means   that   data   is   transferred   without   support   from   an   external   clock   signal.   This   transmission   method   is   perfect   for minimizing   the   required   wires   and   I/O   pins,   but   it   does   mean   we   need   to   put   some   extra   effort   into   reliably   transferring   and receiving data.

My Problem Reading the serial data .... 1 = 49 !!!

When I try the code for the first time, I can not see the expected value on the Arduino serial monitor. My main code simply sends a number to communicate the command, only 1 or 2. This operation seems to be really easy and I do not understand why it does not work properly. I   check   the   code   but   it   seems   correct   so   ..   I   try   to   connect   the   txd   pin   of   the   master   card   to   the   Arduino   serial   monitor   and   ...   the   correct value is on the screen! The   problem   exists   from   the   master   to   the   slave,   to   understand   why   ...   I   make   a   temporary   change   to   my   master   code   and   generate   a   wide range   of   random   numbers   and   the   slave   code   that   prints   all   the   value   received   from   the   master   to   the   Arduino   serial   monitor,   so   the   text   is on screen and I understand: it is the ASCII code !!!

What is the ASCII Code?

The   American   Standard   Code   for   Information   Interchange   (acronym:   ASCII)   is   a   character-encoding   scheme   based   on   the   ordering   of   the w:English   alphabet.   ASCII   codes   represent   text   in   computers,   communications   equipment,   and   other   devices   that   use   text.   Most   modern character-encoding schemes, which support many more characters than did the original, are based on ASCII. At   this   point   I   make   the   changes   on   the   master   and   slave   code,   when   the   master   transmit   the   random   command   send   a   value   in   ASCII code, so ... 1=49 and 2=50 this is the solution! After the changes on the Arduino codes everything works good. The changes in the Arduino slave code concern the "IF" control and the serial value read:   int c = mySerial.read();// read the value on serial rxd pin if (c==49){// the ASCII value for "1"   if (c==50){// the ASCII value for "2"

Wired Communication from Master Board to Slave board

To   complete   the   assignment   of      this   week   I   will   try   to   use   the   serial   communication   protocol   and   two   of   my   cards   made   in   fablab     by me.

The correct wiring:

Studying the serial protocol I understood two basic rules that I have to respect when I physically connect my two cards: 1- The TXD pin of the Master must be connected to the RXD pin of the slave and vice versa. 2- The two cards must have the GND in common

Now   I   have   to   write   a   software   code   for   my   boards,   using   Arduino   IDE   and   integrated   serial   monitoring   tools,   I   can   do   it   more   easily. In my code I need the RANDOM function to generate commands and the SERIAL function to write and read the value. I think it's a good idea to read the documentation of these functions in the   Official Arduino reference guide . Below is the information of the official guide, which I will study to learn how to use the two functions.

random()

[Random Numbers] Description The random function generates pseudo-random numbers. Syntax random(max) random(min, max) Parameters min - lower bound of the random value, inclusive (optional) max - upper bound of the random value, exclusive Example Code: // print a random number from 10 to 19   randNumber = random (10, 20);   Serial.println(randNumber);

Serial

[Communication] Description Used   for   communication   between   the   Arduino   board   and   a   computer   or   other   devices.   All   Arduino   boards   have   at   least   one   serial port   (also   known   as   a   UART   or   USART):   Serial.   It   communicates   on   digital   pins   0   (RX)   and   1   (TX)   as   well   as   with   the   computer   via   USB. Thus, if you use these functions, you cannot also use pins 0 and 1 for digital input or output. You   can   use   the   Arduino   environment’s   built-in   serial   monitor   to   communicate   with   an   Arduino   board.   Click   the   serial   monitor button in the toolbar and select the same baud rate used in the call to begin().

Serial.begin()

Description Sets   the   data   rate   in   bits   per   second   (baud)   for   serial   data   transmission.   For   communicating   with   the   computer,   use   one   of   these rates:   300,   600,   1200,   2400,   4800,   9600,   14400,   19200,   28800,   38400,   57600,   or   115200.   You   can,   however,   specify   other   rates   -   for example, to communicate over pins 0 and 1 with a component that requires a particular baud rate. An optional second argument configures the data, parity, and stop bits. The default is 8 data bits, no parity, one stop bit. Syntax Serial.begin(speed) Serial.begin(speed, config) Example Code:  Serial.begin(9600); // opens serial port, sets data rate to 9600 bps

Serial.read()

Description Reads incoming serial data. read() inherits from the Stream utility class. Syntax Serial.read() Example Code:  value= Serial.read();

Serial.write()

Description Writes binary data to the serial port. This data is sent as a byte or series of bytes; to send the characters representing the digits of a number use the print() function instead. Syntax Serial.write(val) Serial.write(str) Serial.write(buf, len)  Example Code: Serial.write(45); // send a byte with the value 45

Start to Write the Code

I have the elements of programming to write my "wiring" code in Arduino IDE and start to write for  the  Master and Slave software.