File content as of revision 0:36b37fd10b58:

#include "mbed.h"
#include "string"
#include "vector"

DigitalOut led(LED1);

Serial pc(USBTX, USBRX); //rtosの機能を使うときはSerialではなくRawSerialを使えとの情報をみてこうしています。

char data[100];
int data_index = 0;

std::vector<std::string> separate_string(std::string input) 
{
    std::vector<std::string> return_data; 
    std::string separator = std::string(",");
    int separator_length = separator.length();
    std::string::size_type offset = std::string::size_type(0);
    while(1)
    {
        int pos = input.find(separator, offset);             
        if (pos == std::string::npos) 
        {
            return_data.push_back(input.substr(offset));
            break;
        }
        return_data.push_back(input.substr(offset,pos-offset));
        offset = pos + separator_length;
    }
    return return_data;
}


 
int main(void){
    while(1){
      if (!pc.readable()) continue;

        char c = pc.getc();
        data[data_index++] = c;
        if (c == '\n')
        {
            data[data_index] = '\0';
            std::string str;
            str = data;
            std::vector<std::string> data_list = separate_string(str);
            for(int i=0;data_list.size();++i)
            {
                pc.puts(data_list[i].c_str());
                pc.puts("+");
            }
            data_index = 0;
        }
        
    }
}