File content as of revision 0:3355c5b6d8fd:

//UART FLUSH()

// This program is further improvement of circular buffer concepts
/* Note : In Serial class library /or RawSerial class library there is no flush() command.
Sometimes buffer clearing process require when you want to compare receiving data with pre-stored value
or when doing some string related operation, because if you not clear UART buffer you will get old stored data.
*/

/*Note : simple way to clear Buffer : Read it , & reset all UART process related counter.*/

//PROGRAM SUBJECT : UART BUFFER CLEAR / FLUSH()
//Date : 24 July 2020 Version 1.0
//JAYDEEP SHAH -- radhey04ec@gmail.com

// I am sending one by one characters to slave and slave provide response according it , Ex : 'T' = Test Mode

#include "mbed.h"
#define BUFFER_SIZE 90   //SIZE OF BUFFER   ---DEPENDS ON YOUR DATA SIZE  --This is circular buffer

char rxBuffer[BUFFER_SIZE];  //CREATE CIRCULAR BUFFER  -- TO STORE RECEIVE DATA

unsigned int bufferReadingIndex=0;  //CREATE POINTER TO READ DATA FROM UART AND STORE INTO ARRAY

unsigned int i=0; //counter to read data from buffer Array

// 0 - Rx - PA_0   : Board Tx ___ Arduino Connector socket >>> First_pin _Orange  -- If FTDI CABLE USE
// 1 - Tx - PA_1   : Board Rx ____ Arduino connector socket  >>> Second_pin _red  -- If FTDI CABLE USE

//If you use only Serial calss , there is chance of damage OS because of MUTEX GUARD

//use RawSerial class
RawSerial UT(PA_0,PA_1);  //UART PIN DECLARATION
RawSerial pc(USBTX,USBRX);  //HOST PC TERMINAL  - 9600 BAUD WITH 8-N-1 STTING

//NOTE : UT OBJ FOR SLAVE BOARD & pc OBJ FOR TERMINAL

//DEFINE Rx Interrupt function --DECLARATION
void RxInterrupt(void);

//Function that read response data
void response(void);

//FLUSH() UART

void FLUSH(void); //Function declaration only

int main()
{
UT.baud(57600);  //BAUD RATE SETTING
UT.format(8,Serial::None,1);   //FORMAT OF UART COMMUNICATION

//INTERRUPT ATTACHMENT WHEN RECEIVE DATA
UT.attach(&RxInterrupt,Serial::RxIrq);

pc.printf("\n TESTING TURN ON : \n");
wait(1);

UT.putc('T');  //ENTER IN TEST MODE  -- SLAVE BOARD ENTER INTO TEST MODE
wait(0.5);
response();  //Read Response from Slave 
FLUSH(); // BEFORE SENDING /RECEIVING NEW DATA

ThisThread::sleep_for(1000);

UT.putc('d');   // RED LED OF SLAVE BOARD ON
wait(1);
response(); //Read Response from Slave
FLUSH(); // BEFORE SENDING /RECEIVING NEW DATA
ThisThread::sleep_for(5000);


UT.putc('b');  // RED LED OF SLAVE BOARD OFF
wait(1);
response();  //Read Response from slave
FLUSH(); // BEFORE SENDING /RECEIVING NEW DATA
ThisThread::sleep_for(1000);

UT.putc('Q');  //QUIT FROM TEST MODE -- NORMAL MODE SELECT
wait(1);
response();//Read response from Slave
FLUSH(); // BEFORE SENDING /RECEIVING NEW DATA
ThisThread::sleep_for(3000);

while(1)
{
}

}


void RxInterrupt()      //if Rx buffer have data --- Interrupt call
{
    if(UT.readable())  //IF data available
    {
        rxBuffer[bufferReadingIndex++] = UT.getc();   // read and store into Buffer
        if(bufferReadingIndex >= BUFFER_SIZE)  // If limit cross
        {
            bufferReadingIndex =0; // RESET CONTER
        }
    }
}

void response()  //FUNCTION TO READ DATA
{
    char rxByte;

    while(i != bufferReadingIndex)  //READ WHILE COMPLETE DATA NOT RECEIVED
    {
        rxByte = rxBuffer[i];  //READ DATA ONE BY ONE CHARACTER
        pc.putc(rxByte); // SEND ON TERMINAL
        i++;  //COUNTER INCREMENT
        
        if(i >= BUFFER_SIZE) //IF LIMIT CROSS
        {
            i = 0;   //RESET COUNTER
        }
    }
}

void FLUSH()            //FLUSH FUNCTIONS
{
    RxInterrupt(); // This is because read data if something available in UART buffer
    
    //Counters which are related with UART reading process make it zero again
    i = 0U;
    bufferReadingIndex = 0U;   
    
}