File content as of revision 1:acf14b6dd1be:

//master
#include "mbed.h"
#include <stdlib.h>

I2C master(p28, p27);        // sda, scl
Serial pc_master(USBTX, USBRX); // tx, rx
DigitalOut success(LED1);
DigitalOut fail(LED2);
DigitalIn read(p29);

const int SLAVEADDR = 0x88; // define the I2C Slave Address (mbed 2)
char cmd[2];
char buf[50];

void i2c_write(char * data) {
    int ack = master.write(SLAVEADDR, cmd, 2); // Send command string
    if (ack)
        fail=!fail;
    else {
        pc_master.printf("Master is writing..\n");
        success=!success;
    }
}

void i2c_read(char * buf) {
    /*
    int ack = master.read(SLAVEADDR, buf, 6);
    if (ack)
        fail=!fail;
    else {
        pc_master.printf("Slave sent: %s\n", buf);
        success=!success;
    }
    */
    int ack, data, scan_counter;
    scan_counter = 0;
    while(1)
    {
        data=master.read(ack);
        if(data==0xFF)
        {
            pc_master.printf("Scan finish..\n");
            break;
        }
        else
        {
            pc_master.printf("data %d reads %d\n",scan_counter++, data);
        }
    }
}

void i2c_test() {
    master.start();
    cmd[0] = 'U';
    cmd[1] = 'S';
    while (1) {
        if (read) {
            i2c_read(buf);
        } else {
            i2c_write(cmd);
        }
        wait(0.07);
    }
}

void i2c_test2() {
    //send signal to mbed2 and wait for response
    master.start();
    cmd[0] = 'C';
    while (master.write(SLAVEADDR, cmd, 2)) {
        fail=!fail;
    }
    int ack = 1;
    while (1) {
        if (read) {
            while (ack) {
                ack = master.read(SLAVEADDR, buf, 2);
            }
            success = 1;
            //pc_master.printf("Slave sent: $s\n", buf);
            break;
        }
    }
}

void master_write() {
    char cmd[] = "scan";
    while (master.write(SLAVEADDR, cmd, 4)) {
        fail=1;
    }
    fail = 0;
}

void master_read() {
    /*
    char * data[2];
    for (int i=0; i<2; i++) {
        int ack = 1;
        while (ack) {
            ack = master.read(SLAVEADDR, data[i], 10);
            fail = 1;
        }
        fail = 0;
    }
    pc_master.printf("master gets: %s  and %s", *(data[0]), *(data[1]));
    */
    pc_master.printf("master starts reading\n");
    char data_read[64*5+1];
    for(int i=0;i<64*5;i++)
    {
        data_read[i]=(char)49;
    }
    master.read(SLAVEADDR|1, data_read, 64*5, true);
    for(int i=0;i<64;i++)
    {
      pc_master.printf("master gets: %c%c%c%c%c\n", data_read[5*i],data_read[5*i+1],data_read[5*i+2],data_read[5*i+3],data_read[5*i+4]);
    }
    pc_master.printf("master finishes reading\n");
}

void m2s_scan() {
    pc_master.printf("master sends command..\n");
    master_read();
    master_write();
    
    master_read();
    master_read();
}