Electronic Coin Bank

#include "mbed.h"
#include "SDFileSystem.h"
#include "uLCD_4DGL.h"
#include "Servo.h"
#include <Timer.h>

uLCD_4DGL LCD(p13, p14, p11);
SDFileSystem sd(p5, p6, p7, p8, "sd"); //SD card
Serial  blue(p9,p10);
Servo lock(p21);
AnalogIn IR1(p17), IR2(p18), IR3(p19), IR4(p20);
char pw[] = {'p','a','s','s','w','o','r','d'};
int mode=0; //0=not logged in, 1=logged in, 2=logged in and inputting new pw
bool locked=1;
float savings=0.0f;
FILE *sd_file;
Timer t;

void blue_recv(){
    while(blue.readable()){
        switch(mode){
            case 0: {
                int newmode=1;
                for (int i=0; i<8; i++){
                    if (blue.getc()!=pw[i])
                        newmode=0;
                }
                if(newmode==0){
                    LCD.cls();
                    LCD.printf("\n\rIncorrect password. Try again.\n\r");
                }
                mode=newmode;
                break;
            }
            case 1: {
                char select=blue.getc();
                switch(select){
                    case '1': {
                        locked=!locked;
                        break;
                    }
                    case '2': {
                        mode=2;
                        break;
                    }
                    case '3': {
                        savings=0.0;
                        break;
                    }
                    case '4': {
                        mode=0;
                        break;
                    }
                }
                break;
            }
            case 2: {
                for (int i=0; i<8; i++){
                    pw[i]=blue.getc();
                }
                LCD.cls();
                LCD.printf("\n\rNew password has been set.\n\r");
                wait(2);
                mode=1;
                break;
            }
        }
    }
}

int main(){
    t.start();
    blue.baud(9600);
    blue.attach(&blue_recv, Serial::RxIrq);
    int oldmode=-1;
    float oldsavings=-2.0f;

    while(1){
        if(locked){
            lock=1.0;
        }else{
            lock=0.0;
        }
        if(IR1<0.3){
            savings+=0.10;
        }else if(IR2<0.3){
            savings+=0.01;
        }else if(IR3<0.3){
            savings+=0.05;
        }else if(IR4<0.3){
            savings+=0.25;
        }
        if(oldmode!=mode || oldsavings!=savings){
            LCD.cls();
            switch(mode){
                case 0: {
                    LCD.printf("\n\rPlease enter password to log in.\n\r");
                    break;
                }
                case 1: {
                    LCD.printf("\n\rYou're logged in.\n1=lock/unlock\n2=reset password\n3=reset balance\n4=log out\n\r");
                    break;
                }
                case 2: {
                    LCD.printf("\n\rPlease enter your new 8-character password.\n\r");
                    break;
                }
            }
            LCD.printf("\n\rTotal savings:\n\r$%.02f\n\r", savings);
            oldmode=mode;
            if(oldsavings!=savings){
                sd_file = fopen("/sd/savings.csv","a");
                fprintf(sd_file, "$%.02f, %d\n", savings, t.read_ms());
                oldsavings = savings;
                fclose(sd_file);
            }
        }
    }
}